Commit 18246ced by Jonathan Wakely Committed by Jonathan Wakely

faq.xml: Link to manual.

2010-04-22  Jonathan Wakely  <jwakely.gcc@gmail.com>

	* doc/xml/faq.xml: Link to manual.
	* doc/xml/manual/using.xml: Expand dynamic libraries section.
	* doc/xml/manual/strings.xml: Mention shrink_to_fit() member.
	* doc/xml/manual/prerequisites.xml: Link to doxygen requirements.
	* doc/xml/manual/appendix_contributing.xml: Update Bash version.
	* doc/html/*: Regenerate.

From-SVN: r158624
parent bc58d7e1
2010-04-22 Jonathan Wakely <jwakely.gcc@gmail.com>
* doc/xml/faq.xml: Link to manual.
* doc/xml/manual/using.xml: Expand dynamic libraries section.
* doc/xml/manual/strings.xml: Mention shrink_to_fit() member.
* doc/xml/manual/prerequisites.xml: Link to doxygen requirements.
* doc/xml/manual/appendix_contributing.xml: Update Bash version.
* doc/html/*: Regenerate.
2010-04-13 Ian Lance Taylor <iant@google.com>
* include/backward/hash_map: Don't #include "backward_warning.h"
......
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>API and Source Level Documentation</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk02.html" title="" /><link rel="prev" href="bk02.html" title="" /><link rel="next" href="bk03.html" title="" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">API and Source Level Documentation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk02.html">Prev</a> </td><th width="60%" align="center"></th><td width="20%" align="right"> <a accesskey="n" href="bk03.html">Next</a></td></tr></table><hr /></div><div class="article" title="API and Source Level Documentation"><div class="titlepage"><div><div><h2 class="title"><a id="api"></a>API and Source Level Documentation</h2></div><div><p class="copyright">Copyright ©
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>API Documentation</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk02.html" title="" /><link rel="prev" href="bk02.html" title="" /><link rel="next" href="bk03.html" title="" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">API Documentation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk02.html">Prev</a> </td><th width="60%" align="center"></th><td width="20%" align="right"> <a accesskey="n" href="bk03.html">Next</a></td></tr></table><hr /></div><div class="article" title="API Documentation"><div class="titlepage"><div><div><h2 class="title"><a id="api"></a>API Documentation</h2></div><div><p class="copyright">Copyright ©
2008
,
2010
<a class="ulink" href="http://www.fsf.org/" target="_top">FSF
</a>
</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id561368"></a><p>
</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id515244"></a><p>
<a class="link" href="manual/license.html" title="License">License
</a>
</p></div></div></div><hr /></div><p>
The GNU C++ library sources have been specially formatted so that with the
proper invocation of another tool (Doxygen), a set of HTML pages
are generated from the sources files themselves. The resultant
documentation is referred to as Source Level Documentation, and is
useful for examining the signatures of public member functions for
the library classes, finding out what is in a particular include
file, looking at inheritance diagrams, etc.
The GNU C++ library sources have been specially formatted so that
with the proper invocation of another tool (Doxygen), a set of
indexed reference material can generated from the sources files
themselves. The resultant documentation is referred to as the API
documentation, and is useful for examining the signatures of public
member functions for the library classes, finding out what is in a
particular include file, looking at inheritance diagrams, etc.
</p><p>
The source-level documentation for the most recent releases can be
viewed online:
The API documentation, rendered into HTML, can be viewed online:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-3.4/index.html" target="_top">for the 3.4 release
</a>
......@@ -39,16 +40,14 @@ viewed online:
</a>
(For the main development tree; see the date on the first page.)
</p></li></ul></div><p>
This generated HTML collection, as above, is also available for download in the libstdc++ snapshots directory at
The rendered HTML, as above, is also available for download on the
gcc.org site in a directory located at
<code class="literal">&lt;URL:ftp://gcc.gnu.org/pub/gcc/libstdc++/doxygen/&gt;</code>.
You will almost certainly need to use one of the
<a class="ulink" href="http://gcc.gnu.org/mirrors.html" target="_top">mirror sites</a> to download
the tarball. After unpacking, simply load libstdc++-html-*/index.html
the tarball. After unpacking, simply load libstdc++-html-*/index.html
into a browser.
</p><p>
Documentation for older releases is available for download only, not
online viewing.
</p><p>
In addition, an initial set of man pages are also available in the
same place as the HTML collections. Start with C++Intro(3).
In addition, a rendered set of man pages are available in the same
location specified above. Start with C++Intro(3).
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"> </td><td width="20%" align="center"><a accesskey="h" href="spine.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="prev" href="manual/backwards.html" title="Backwards Compatibility" /><link rel="next" href="api.html" title="API Documentation" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="manual/backwards.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="api.html">Next</a></td></tr></table><hr /></div><div class="book"><div class="titlepage"><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="article"><a href="api.html">API Documentation</a></span></dt></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="manual/backwards.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="api.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Backwards Compatibility </td><td width="20%" align="center"><a accesskey="h" href="spine.html">Home</a></td><td width="40%" align="right" valign="top"> API Documentation</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="prev" href="api.html" title="API and Source Level Documentation" /><link rel="next" href="faq.html" title="Frequently Asked Questions" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="api.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="faq.html">Next</a></td></tr></table><hr /></div><div class="book"><div class="titlepage"><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="article"><a href="faq.html">Frequently Asked Questions</a></span></dt></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="api.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="faq.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">API and Source Level Documentation </td><td width="20%" align="center"><a accesskey="h" href="spine.html">Home</a></td><td width="40%" align="right" valign="top"> Frequently Asked Questions</td></tr></table></div></body></html>
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="prev" href="api.html" title="API Documentation" /><link rel="next" href="faq.html" title="Frequently Asked Questions" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="api.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="faq.html">Next</a></td></tr></table><hr /></div><div class="book"><div class="titlepage"><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="article"><a href="faq.html">Frequently Asked Questions</a></span></dt></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="api.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="faq.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">API Documentation </td><td width="20%" align="center"><a accesskey="h" href="spine.html">Home</a></td><td width="40%" align="right" valign="top"> Frequently Asked Questions</td></tr></table></div></body></html>
......@@ -4,7 +4,7 @@
2008
<a class="ulink" href="http://www.fsf.org" target="_top">FSF</a>
</p></div></div><hr /></div><div class="qandaset" title="Frequently Asked Questions"><a id="id571249"></a><dl><dt>1. <a href="faq.html#faq.info">General Information</a></dt><dd><dl><dt>1.1. <a href="faq.html#faq.what">
</p></div></div><hr /></div><div class="qandaset" title="Frequently Asked Questions"><a id="id621954"></a><dl><dt>1. <a href="faq.html#faq.info">General Information</a></dt><dd><dl><dt>1.1. <a href="faq.html#faq.what">
What is libstdc++?
</a></dt><dt>1.2. <a href="faq.html#faq.why">
Why should I use libstdc++?
......@@ -315,12 +315,15 @@
and <span class="command"><strong>ldconfig</strong></span> for more information. The dynamic
linker has different names on different platforms but the man page
is usually called something such as <code class="filename">ld.so/rtld/dld.so</code>.
</p><p>
Using LD_LIBRARY_PATH is not always the best solution, <a class="link" href="manual/using_dynamic_or_shared.html#manual.intro.using.linkage.dynamic" title="Finding Dynamic or Shared Libraries">Finding Dynamic or Shared
Libraries</a> in the manual gives some alternatives.
</p></td></tr><tr class="question" title="3.5."><td align="left" valign="top"><a id="faq.what_is_libsupcxx"></a><a id="q-what_is_libsupcxx"></a><p><b>3.5.</b></p></td><td align="left" valign="top"><p>
What's libsupc++?
</p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-what_is_libsupcxx"></a></td><td align="left" valign="top"><p>
If the only functions from <code class="filename">libstdc++.a</code>
which you need are language support functions (those listed in
<a class="link" href="manual/support.html" title="Part II.  Support">clause 18</a> of the
<a class="link" href="manual/support.html" title="Chapter 4.  Support">clause 18</a> of the
standard, e.g., <code class="function">new</code> and
<code class="function">delete</code>), then try linking against
<code class="filename">libsupc++.a</code>, which is a subset of
......@@ -647,8 +650,9 @@
typo, or wrong visibility, or you just plain forgot, etc).
</p><p>
More information, including how to optionally enable/disable the
checks, is available
<a class="link" href="manual/bk01pt03ch08.html" title="Chapter 8. Concept Checking">here</a>.
checks, is available in the
<a class="link" href="manual/bk01pt02ch05s02.html" title="Concept Checking">Diagnostics</a>.
chapter of the manual.
</p></td></tr><tr class="question" title="6.6."><td align="left" valign="top"><a id="faq.dlopen_crash"></a><a id="q-dlopen_crash"></a><p><b>6.6.</b></p></td><td align="left" valign="top"><p>
Program crashes when using library code in a
dynamically-loaded library
......@@ -685,7 +689,7 @@
list::size() is O(n)!
</p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-list_size_on"></a></td><td align="left" valign="top"><p>
See
the <a class="link" href="manual/containers.html" title="Part VII.  Containers">Containers</a>
the <a class="link" href="manual/containers.html" title="Chapter 9.  Containers">Containers</a>
chapter.
</p></td></tr><tr class="question" title="6.9."><td align="left" valign="top"><a id="faq.easy_to_fix"></a><a id="q-easy_to_fix"></a><p><b>6.9.</b></p></td><td align="left" valign="top"><p>
Aw, that's easy to fix!
......@@ -869,6 +873,6 @@
    </p></div><p>
The copy will take O(n) time and the swap is constant time.
</p><p>
See <a class="link" href="manual/bk01pt05ch13s05.html" title="Shrink to Fit">Shrink-to-fit
See <a class="link" href="manual/strings.html#strings.string.shrink" title="Shrink to Fit">Shrink-to-fit
strings</a> for a similar solution for strings.
</p></td></tr></tbody></table></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk03.html">Up</a></td><td width="40%" align="right"> </td></tr><tr><td width="40%" align="left" valign="top"> </td><td width="20%" align="center"><a accesskey="h" href="spine.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Part IX.  Algorithms</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; , &#10; algorithm&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library" /><link rel="prev" href="bk01pt08ch19s02.html" title="One Past the End" /><link rel="next" href="bk01pt09pr02.html" title="" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Part IX
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 11.  Algorithms</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; , &#10; algorithm&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt02.html" title="Part II.  Standard Contents" /><link rel="prev" href="iterators.html" title="Chapter 10.  Iterators" /><link rel="next" href="numerics.html" title="Chapter 12.  Numerics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 11
Algorithms
</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt08ch19s02.html">Prev</a> </td><th width="60%" align="center">The GNU C++ Library</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt09pr02.html">Next</a></td></tr></table><hr /></div><div class="part" title="Part IX.  Algorithms"><div class="titlepage"><div><div><h1 class="title"><a id="manual.algorithms"></a>Part IX. 
</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="iterators.html">Prev</a> </td><th width="60%" align="center">Part II. 
Standard Contents
</th><td width="20%" align="right"> <a accesskey="n" href="numerics.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 11.  Algorithms"><div class="titlepage"><div><div><h2 class="title"><a id="std.algorithms"></a>Chapter 11. 
Algorithms
<a id="id638163" class="indexterm"></a>
</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="preface"><a href="bk01pt09pr02.html"></a></span></dt><dt><span class="chapter"><a href="bk01pt09ch20.html">20. Mutating</a></span></dt><dd><dl><dt><span class="sect1"><a href="bk01pt09ch20.html#algorithms.mutating.swap"><code class="function">swap</code></a></span></dt><dd><dl><dt><span class="sect2"><a href="bk01pt09ch20.html#algorithms.swap.specializations">Specializations</a></span></dt></dl></dd></dl></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt08ch19s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt09pr02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">One Past the End </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div></body></html>
<a id="id505811" class="indexterm"></a>
</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="algorithms.html#std.algorithms.mutating">Mutating</a></span></dt><dd><dl><dt><span class="sect2"><a href="algorithms.html#algorithms.mutating.swap"><code class="function">swap</code></a></span></dt></dl></dd></dl></div><p>
The neatest accomplishment of the algorithms sect1 is that all the
work is done via iterators, not containers directly. This means two
important things:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
Anything that behaves like an iterator can be used in one of
these algorithms. Raw pointers make great candidates, thus
built-in arrays are fine containers, as well as your own
iterators.
</p></li><li class="listitem"><p>
The algorithms do not (and cannot) affect the container as a
whole; only the things between the two iterator endpoints. If
you pass a range of iterators only enclosing the middle third of
a container, then anything outside that range is inviolate.
</p></li></ol></div><p>
Even strings can be fed through the algorithms here, although the
string class has specialized versions of many of these functions
(for example, <code class="code">string::find()</code>). Most of the examples
on this page will use simple arrays of integers as a playground
for algorithms, just to keep things simple. The use of
<span class="emphasis"><em>N</em></span> as a size in the examples is to keep things
easy to read but probably won't be valid code. You can use wrappers
such as those described in
the <a class="link" href="containers.html" title="Chapter 9.  Containers">containers sect1</a> to keep
real code readable.
</p><p>
The single thing that trips people up the most is the definition
of <span class="emphasis"><em>range</em></span> used with iterators; the famous
"past-the-end" rule that everybody loves to hate. The
<a class="link" href="iterators.html" title="Chapter 10.  Iterators">iterators sect1</a> of this
document has a complete explanation of this simple rule that seems
to cause so much confusion. Once you
get <span class="emphasis"><em>range</em></span> into your head (it's not that hard,
honest!), then the algorithms are a cakewalk.
</p><div class="sect1" title="Mutating"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.algorithms.mutating"></a>Mutating</h2></div></div></div><div class="sect2" title="swap"><div class="titlepage"><div><div><h3 class="title"><a id="algorithms.mutating.swap"></a><code class="function">swap</code></h3></div></div></div><div class="sect3" title="Specializations"><div class="titlepage"><div><div><h4 class="title"><a id="algorithms.swap.specializations"></a>Specializations</h4></div></div></div><p>If you call <code class="code"> std::swap(x,y); </code> where x and y are standard
containers, then the call will automatically be replaced by a call to
<code class="code"> x.swap(y); </code> instead.
</p><p>This allows member functions of each container class to take over, and
containers' swap functions should have O(1) complexity according to
the standard. (And while "should" allows implementations to
behave otherwise and remain compliant, this implementation does in
fact use constant-time swaps.) This should not be surprising, since
for two containers of the same type to swap contents, only some
internal pointers to storage need to be exchanged.
</p></div></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="iterators.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="numerics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 10. 
Iterators
 </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 12. 
Numerics
</td></tr></table></div></body></html>
......@@ -30,8 +30,8 @@ Removal of <code class="filename">ext/tree</code>, moved to <code class="filenam
</p><p>Symbol versioning introduced for shared library.</p><p>Removal of include <code class="filename">backward/strstream.h</code>.</p><p>Allocator changes. Change <code class="code">__malloc_alloc</code> to <code class="code">malloc_allocator</code> and <code class="code">__new_alloc</code> to <code class="code">new_allocator</code>. </p><p> For GCC releases from 2.95 through the 3.1 series, defining
<code class="literal">__USE_MALLOC</code> on the gcc command line would change the
default allocation strategy to instead use <code class="code"> malloc</code> and
<code class="function">free</code>. (This same functionality is now spelled <code class="literal">_GLIBCXX_FORCE_NEW</code>, see
<a class="link" href="using_macros.html" title="Macros">this page</a>
<code class="function">free</code>. (This same functionality is now spelled <code class="literal">_GLIBCXX_FORCE_NEW</code>, see
<a class="link" href="using_macros.html" title="Macros">this page</a>
for details.
</p><p>Error handling in iostreams cleaned up, made consistent. </p></div><div class="sect2" title="3.3"><div class="titlepage"><div><div><h3 class="title"><a id="api.rel_330"></a><code class="constant">3.3</code></h3></div></div></div><p>
</p></div><div class="sect2" title="3.4"><div class="titlepage"><div><div><h3 class="title"><a id="api.rel_340"></a><code class="constant">3.4</code></h3></div></div></div><p>
......@@ -75,11 +75,11 @@ _Alloc_traits</code> have been removed.
<span class="type">__alloc</span> to select an underlying allocator that
satisfied memory allocation requests. The selection of this
underlying allocator was not user-configurable.
</p><div class="table"><a id="id653273"></a><p class="title"><b>Table B.1. Extension Allocators</b></p><div class="table-contents"><table summary="Extension Allocators" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Allocator (3.4)</th><th align="left">Header (3.4)</th><th align="left">Allocator (3.[0-3])</th><th align="left">Header (3.[0-3])</th></tr></thead><tbody><tr><td align="left"><code class="classname">__gnu_cxx::new_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/new_allocator.h</code></td><td align="left"><code class="classname">std::__new_alloc</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::malloc_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/malloc_allocator.h</code></td><td align="left"><code class="classname">std::__malloc_alloc_template&lt;int&gt;</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::debug_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/debug_allocator.h</code></td><td align="left"><code class="classname">std::debug_alloc&lt;T&gt;</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::__pool_alloc&lt;T&gt;</code></td><td align="left"><code class="filename">ext/pool_allocator.h</code></td><td align="left"><code class="classname">std::__default_alloc_template&lt;bool,int&gt;</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::__mt_alloc&lt;T&gt;</code></td><td align="left"><code class="filename">ext/mt_allocator.h</code></td><td align="left"> </td><td align="left"> </td></tr><tr><td align="left"><code class="classname">__gnu_cxx::bitmap_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/bitmap_allocator.h</code></td><td align="left"> </td><td align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p> Releases after gcc-3.4 have continued to add to the collection
</p><div class="table"><a id="id433329"></a><p class="title"><b>Table B.1. Extension Allocators</b></p><div class="table-contents"><table summary="Extension Allocators" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Allocator (3.4)</th><th align="left">Header (3.4)</th><th align="left">Allocator (3.[0-3])</th><th align="left">Header (3.[0-3])</th></tr></thead><tbody><tr><td align="left"><code class="classname">__gnu_cxx::new_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/new_allocator.h</code></td><td align="left"><code class="classname">std::__new_alloc</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::malloc_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/malloc_allocator.h</code></td><td align="left"><code class="classname">std::__malloc_alloc_template&lt;int&gt;</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::debug_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/debug_allocator.h</code></td><td align="left"><code class="classname">std::debug_alloc&lt;T&gt;</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::__pool_alloc&lt;T&gt;</code></td><td align="left"><code class="filename">ext/pool_allocator.h</code></td><td align="left"><code class="classname">std::__default_alloc_template&lt;bool,int&gt;</code></td><td align="left"><code class="filename">memory</code></td></tr><tr><td align="left"><code class="classname">__gnu_cxx::__mt_alloc&lt;T&gt;</code></td><td align="left"><code class="filename">ext/mt_allocator.h</code></td><td align="left"> </td><td align="left"> </td></tr><tr><td align="left"><code class="classname">__gnu_cxx::bitmap_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/bitmap_allocator.h</code></td><td align="left"> </td><td align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p> Releases after gcc-3.4 have continued to add to the collection
of available allocators. All of these new allocators are
standard-style. The following table includes details, along with
the first released version of GCC that included the extension allocator.
</p><div class="table"><a id="id594438"></a><p class="title"><b>Table B.2. Extension Allocators Continued</b></p><div class="table-contents"><table summary="Extension Allocators Continued" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Allocator</th><th align="left">Include</th><th align="left">Version</th></tr></thead><tbody><tr><td align="left"><code class="classname">__gnu_cxx::array_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/array_allocator.h</code></td><td align="left">4.0.0</td></tr><tr><td align="left"><code class="classname">__gnu_cxx::throw_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/throw_allocator.h</code></td><td align="left">4.2.0</td></tr></tbody></table></div></div><br class="table-break" /><p>
</p><div class="table"><a id="id432659"></a><p class="title"><b>Table B.2. Extension Allocators Continued</b></p><div class="table-contents"><table summary="Extension Allocators Continued" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Allocator</th><th align="left">Include</th><th align="left">Version</th></tr></thead><tbody><tr><td align="left"><code class="classname">__gnu_cxx::array_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/array_allocator.h</code></td><td align="left">4.0.0</td></tr><tr><td align="left"><code class="classname">__gnu_cxx::throw_allocator&lt;T&gt;</code></td><td align="left"><code class="filename">ext/throw_allocator.h</code></td><td align="left">4.2.0</td></tr></tbody></table></div></div><br class="table-break" /><p>
Debug mode first appears.
</p><p>
Precompiled header support <acronym class="acronym">PCH</acronym> support.
......@@ -143,13 +143,13 @@ Debug mode for <code class="filename">unordered_map</code> and <code class="file
</p><p>
Parallel mode first appears.
</p><p>Variadic template implementations of items in <code class="filename">tuple</code> and
<code class="filename">functional</code>.
<code class="filename">functional</code>.
</p><p>Default <code class="code">what</code> implementations give more elaborate
exception strings for <code class="code">bad_cast</code>,
<code class="code">bad_typeid</code>, <code class="code">bad_exception</code>, and
<code class="code">bad_alloc</code>.
</p><p>
PCH binary files no longer installed. Instead, the source files are installed.
PCH binary files no longer installed. Instead, the source files are installed.
</p><p>
Namespace pb_ds moved to __gnu_pb_ds.
</p></div><div class="sect2" title="4.4"><div class="titlepage"><div><div><h3 class="title"><a id="api.rel_440"></a><code class="constant">4.4</code></h3></div></div></div><p>
......@@ -227,7 +227,7 @@ C++0X features.
</p></li></ul></div><p>
Profile mode first appears.
</p><p>
Support for decimal floating-point arithmetic, including <code class="classname">decimal32</code>, <code class="classname">decimal64</code>, and <code class="classname">decimal128</code>.
Support for decimal floating-point arithmetic, including <code class="classname">decimal32</code>, <code class="classname">decimal64</code>, and <code class="classname">decimal128</code>.
</p><p>
Python pretty-printers are added for use with appropriately-advanced versions of <span class="command"><strong>gdb</strong></span>.
</p><p>
......
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Free Software Needs Free Documentation
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</th><td width="20%" align="right"> <a accesskey="n" href="appendix_gpl.html">Next</a></td></tr></table><hr /></div><div class="appendix" title="Appendix C.  Free Software Needs Free Documentation"><div class="titlepage"><div><div><h2 class="title"><a id="appendix.free"></a>Appendix C. 
Free Software Needs Free Documentation
<a id="id702684" class="indexterm"></a>
<a id="id490083" class="indexterm"></a>
</h2></div></div></div><p>
The biggest deficiency in free operating systems is not in the
software--it is the lack of good free manuals that we can include in
......@@ -35,7 +37,7 @@ restrict it so that we cannot use it.
</p><p>
Given that writing good English is a rare skill among programmers, we
can ill afford to lose manuals this way.
</p><p>
</p><p>
Free documentation, like free software, is a matter of freedom,
not price. The problem with these manuals was not that O'Reilly
Associates charged a price for printed copies--that in itself is fine.
......@@ -119,6 +121,6 @@ prefer copylefted manuals to non-copylefted ones.
that lists free books available from other publishers</a>].
</p><p>Copyright © 2004, 2005, 2006, 2007 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA</p><p>Verbatim copying and distribution of this entire article are
permitted worldwide, without royalty, in any medium, provided this
notice is preserved.</p><p>Report any problems or suggestions to <code class="email">&lt;<a class="email" href="mailto:webmaster@fsf.org">webmaster@fsf.org</a>&gt;</code>.</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="backwards.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix_gpl.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Backwards Compatibility </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix D. 
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Appendix E. GNU Free Documentation License</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt04.html" title="Part IV.  Appendices" /><link rel="prev" href="appendix_gpl.html" title="Appendix D.  GNU General Public License version 3" /><link rel="next" href="../bk02.html" title="" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Appendix E. GNU Free Documentation License</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="appendix_gpl.html">Prev</a> </td><th width="60%" align="center">Part IV. 
Appendices
</th><td width="20%" align="right"> <a accesskey="n" href="../bk02.html">Next</a></td></tr></table><hr /></div><div class="appendix" title="Appendix E. GNU Free Documentation License"><div class="titlepage"><div><div><h2 class="title"><a id="appendix.gfdl-1.2"></a>Appendix E. GNU Free Documentation License</h2></div></div></div><p>
Copyright (C) 2000, 2001, 2002 Free Software Foundation,
<abbr class="abbrev">Inc.</abbr> 51 Franklin <abbr class="abbrev">St</abbr>, Fifth Floor,
Boston, <abbr class="abbrev">MA</abbr> 02110-1301 <abbr class="abbrev">USA</abbr>. Everyone is permitted to copy and
......@@ -390,6 +392,6 @@
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit their
use in free software.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="appendix_gpl.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01ix01.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix D. 
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="appendix_gpl.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt04.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="../bk02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix D. 
<acronym class="acronym">GNU</acronym> General Public License version 3
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</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="appendix_free.html">Prev</a> </td><th width="60%" align="center">Part IV. 
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</th><td width="20%" align="right"> <a accesskey="n" href="appendix_gfdl.html">Next</a></td></tr></table><hr /></div><div class="appendix" title="Appendix D.  GNU General Public License version 3"><div class="titlepage"><div><div><h2 class="title"><a id="appendix.gpl-3.0"></a>Appendix D. 
<acronym class="acronym">GNU</acronym> General Public License version 3
</h2></div></div></div><p>
Version 3, 29 June 2007
......@@ -76,7 +78,7 @@
</p><p>
The precise terms and conditions for copying, distribution and modification
follow.
</p><h2><a id="id703002"></a>
</p><h2><a id="id382653"></a>
TERMS AND CONDITIONS
</h2><h2><a id="gpl-3-definitions"></a>
0. Definitions.
......@@ -617,7 +619,7 @@
waiver of all civil liability in connection with the Program, unless a
warranty or assumption of liability accompanies a copy of the Program in
return for a fee.
</p><h2><a id="id635999"></a>
</p><h2><a id="id421222"></a>
END OF TERMS AND CONDITIONS
</h2><h2><a id="HowToApply"></a>
How to Apply These Terms to Your New Programs
......@@ -675,7 +677,7 @@ under certain conditions; type ‘<code class="literal">show c</code>’ for det
proprietary applications with the library. If this is what you want to do,
use the <acronym class="acronym">GNU</acronym> Lesser General Public License instead of this
License. But first, please read <a class="ulink" href="http://www.gnu.org/philosophy/why-not-lgpl.html" target="_top">http://www.gnu.org/philosophy/why-not-lgpl.html</a>.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="appendix_free.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix_gfdl.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix C. 
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="appendix_free.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt04.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix_gfdl.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix C. 
Free Software Needs Free Documentation
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 14.  Atomics</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; , &#10; atomic&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt02.html" title="Part II.  Standard Contents" /><link rel="prev" href="io_and_c.html" title="Interacting with C" /><link rel="next" href="concurrency.html" title="Chapter 15.  Concurrency" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 14. 
Atomics
</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="io_and_c.html">Prev</a> </td><th width="60%" align="center">Part II. 
Standard Contents
</th><td width="20%" align="right"> <a accesskey="n" href="concurrency.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 14.  Atomics"><div class="titlepage"><div><div><h2 class="title"><a id="std.atomics"></a>Chapter 14. 
Atomics
<a id="id510195" class="indexterm"></a>
</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="atomics.html#std.atomics.api">API Reference</a></span></dt></dl></div><p>
Facilities for atomic operations.
</p><div class="sect1" title="API Reference"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.atomics.api"></a>API Reference</h2></div></div></div><p>
All items are declared in the standard header
file <code class="filename">atomic</code>.
</p><p>
Set of typedefs that map <span class="type">int</span> to
<code class="classname">atomic_int</code>, and so on for all builtin
integral types. Global enumeration <span class="type">memory_order</span> to
control memory ordering. Also includes
<code class="classname">atomic</code>, a class template with member
functions such as <code class="function">load</code> and
<code class="function">store</code> that is instantiable such that
<code class="classname">atomic_int</code> is the base class of
<code class="classname">atomic&lt;int&gt;</code>.
</p><p>
Full API details.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="io_and_c.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="concurrency.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Interacting with C </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 15. 
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happen with misuse of the <code class="classname">auto_ptr</code> class
template (called <acronym class="acronym">AP</acronym> here) would take some
time. Suffice it to say that the use of <acronym class="acronym">AP</acronym>
safely in the presence of copying has some subtleties.
</p><p>
The AP class is a really
nifty idea for a smart pointer, but it is one of the dumbest of
all the smart pointers -- and that's fine.
</p><p>
AP is not meant to be a supersmart solution to all resource
leaks everywhere. Neither is it meant to be an effective form
of garbage collection (although it can help, a little bit).
And it can <span class="emphasis"><em>not</em></span>be used for arrays!
</p><p>
<acronym class="acronym">AP</acronym> is meant to prevent nasty leaks in the
presence of exceptions. That's <span class="emphasis"><em>all</em></span>. This
code is AP-friendly:
</p><pre class="programlisting">
// Not a recommend naming scheme, but good for web-based FAQs.
typedef std::auto_ptr&lt;MyClass&gt; APMC;
extern function_taking_MyClass_pointer (MyClass*);
extern some_throwable_function ();
void func (int data)
{
APMC ap (new MyClass(data));
some_throwable_function(); // this will throw an exception
function_taking_MyClass_pointer (ap.get());
}
</pre><p>When an exception gets thrown, the instance of MyClass that's
been created on the heap will be <code class="function">delete</code>'d as the stack is
unwound past <code class="function">func()</code>.
</p><p>Changing that code as follows is not <acronym class="acronym">AP</acronym>-friendly:
</p><pre class="programlisting">
APMC ap (new MyClass[22]);
</pre><p>You will get the same problems as you would without the use
of <acronym class="acronym">AP</acronym>:
</p><pre class="programlisting">
char* array = new char[10]; // array new...
...
delete array; // ...but single-object delete
</pre><p>
AP cannot tell whether the pointer you've passed at creation points
to one or many things. If it points to many things, you are about
to die. AP is trivial to write, however, so you could write your
own <code class="code">auto_array_ptr</code> for that situation (in fact, this has
been done many times; check the mailing lists, Usenet, Boost, etc).
</p></div><div class="sect2" title="Use in Containers"><div class="titlepage"><div><div><h3 class="title"><a id="auto_ptr.using"></a>Use in Containers</h3></div></div></div><p>
</p><p>All of the <a class="link" href="containers.html" title="Part VII.  Containers">containers</a>
described in the standard library require their contained types
to have, among other things, a copy constructor like this:
</p><pre class="programlisting">
struct My_Type
{
My_Type (My_Type const&amp;);
};
</pre><p>
Note the const keyword; the object being copied shouldn't change.
The template class <code class="code">auto_ptr</code> (called AP here) does not
meet this requirement. Creating a new AP by copying an existing
one transfers ownership of the pointed-to object, which means that
the AP being copied must change, which in turn means that the
copy ctors of AP do not take const objects.
</p><p>
The resulting rule is simple: <span class="emphasis"><em>Never ever use a
container of auto_ptr objects</em></span>. The standard says that
<span class="quote"><span class="quote">undefined</span></span> behavior is the result, but it is
guaranteed to be messy.
</p><p>
To prevent you from doing this to yourself, the
<a class="link" href="ext_compile_checks.html" title="Chapter 29. Compile Time Checks">concept checks</a> built
in to this implementation will issue an error if you try to
compile code like this:
</p><pre class="programlisting">
#include &lt;vector&gt;
#include &lt;memory&gt;
void f()
{
std::vector&lt; std::auto_ptr&lt;int&gt; &gt; vec_ap_int;
}
</pre><p>
Should you try this with the checks enabled, you will see an error.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="memory.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="memory.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="shared_ptr.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 11. Memory </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> shared_ptr</td></tr></table></div></body></html>
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</p><div class="sect2" title="Design"><div class="titlepage"><div><div><h3 class="title"><a id="allocator.bitmap.design"></a>Design</h3></div></div></div><p>
As this name suggests, this allocator uses a bit-map to keep track
of the used and unused memory locations for it's book-keeping
......@@ -103,7 +103,7 @@ else return false.</p></li></ol></div><p>
</p><p>
Consider a block of size 64 ints. In memory, it would look like this:
(assume a 32-bit system where, size_t is a 32-bit entity).
</p><div class="table"><a id="id620814"></a><p class="title"><b>Table 33.1. Bitmap Allocator Memory Map</b></p><div class="table-contents"><table summary="Bitmap Allocator Memory Map" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left">268</td><td align="left">0</td><td align="left">4294967295</td><td align="left">4294967295</td><td align="left">Data -&gt; Space for 64 ints</td></tr></tbody></table></div></div><br class="table-break" /><p>
</p><div class="table"><a id="id379923"></a><p class="title"><b>Table 20.1. Bitmap Allocator Memory Map</b></p><div class="table-contents"><table summary="Bitmap Allocator Memory Map" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left">268</td><td align="left">0</td><td align="left">4294967295</td><td align="left">4294967295</td><td align="left">Data -&gt; Space for 64 ints</td></tr></tbody></table></div></div><br class="table-break" /><p>
The first Column(268) represents the size of the Block in bytes as
seen by the Bitmap Allocator. Internally, a global free list is
used to keep track of the free blocks used and given back by the
......@@ -192,20 +192,20 @@ For map/multimap: k = 12, and c = 4 (int and double), we get: 37.524%
_S_refill_pool which does the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Gets more memory from the Global Free List of the Required
size.
size.
</p></li><li class="listitem"><p>
Adjusts the size for the next call to itself.
Adjusts the size for the next call to itself.
</p></li><li class="listitem"><p>
Writes the appropriate headers in the bit-maps.
</p></li><li class="listitem"><p>
Sets the use count for that super-block just allocated to 0
(zero).
(zero).
</p></li><li class="listitem"><p>
All of the above accounts to maintaining the basic invariant
for the allocator. If the invariant is maintained, we are
sure that all is well. Now, the same process is applied on
the newly acquired free blocks, which are dispatched
accordingly.
accordingly.
</p></li></ul></div></li></ol></div><p>
Thus, you can clearly see that the allocate function is nothing but a
combination of the next-fit and first-fit algorithm optimized ONLY for
......@@ -337,4 +337,4 @@ equivalent.</p></li><li class="listitem"><p>And also this would preserve the cac
sizeof(size_t) x 8 which is the number of bits in an integer,
which can fit exactly in a CPU register. Hence, the term given is
exponential growth of the internal pool.
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>bitset</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="associative.html" title="Chapter 17. Associative" /><link rel="prev" href="associative.html" title="Chapter 17. Associative" /><link rel="next" href="containers_and_c.html" title="Chapter 18. Interacting with C" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">bitset</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="associative.html">Prev</a> </td><th width="60%" align="center">Chapter 17. Associative</th><td width="20%" align="right"> <a accesskey="n" href="containers_and_c.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="bitset"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="containers.associative.bitset"></a>bitset</h2></div></div></div><div class="sect2" title="Size Variable"><div class="titlepage"><div><div><h3 class="title"><a id="associative.bitset.size_variable"></a>Size Variable</h3></div></div></div><p>
No, you cannot write code of the form
</p><pre class="programlisting">
#include &lt;bitset&gt;
void foo (size_t n)
{
std::bitset&lt;n&gt; bits;
....
}
</pre><p>
because <code class="code">n</code> must be known at compile time. Your
compiler is correct; it is not a bug. That's the way templates
work. (Yes, it <span class="emphasis"><em>is</em></span> a feature.)
</p><p>
There are a couple of ways to handle this kind of thing. Please
consider all of them before passing judgement. They include, in
no particular order:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>A very large N in <code class="code">bitset&lt;N&gt;</code>.</p></li><li class="listitem"><p>A container&lt;bool&gt;.</p></li><li class="listitem"><p>Extremely weird solutions.</p></li></ul></div><p>
<span class="emphasis"><em>A very large N in
<code class="code">bitset&lt;N&gt;</code>.  </em></span> It has been
pointed out a few times in newsgroups that N bits only takes up
(N/8) bytes on most systems, and division by a factor of eight is
pretty impressive when speaking of memory. Half a megabyte given
over to a bitset (recall that there is zero space overhead for
housekeeping info; it is known at compile time exactly how large
the set is) will hold over four million bits. If you're using
those bits as status flags (e.g.,
<span class="quote"><span class="quote">changed</span></span>/<span class="quote"><span class="quote">unchanged</span></span> flags), that's a
<span class="emphasis"><em>lot</em></span> of state.
</p><p>
You can then keep track of the <span class="quote"><span class="quote">maximum bit used</span></span>
during some testing runs on representative data, make note of how
many of those bits really need to be there, and then reduce N to
a smaller number. Leave some extra space, of course. (If you
plan to write code like the incorrect example above, where the
bitset is a local variable, then you may have to talk your
compiler into allowing that much stack space; there may be zero
space overhead, but it's all allocated inside the object.)
</p><p>
<span class="emphasis"><em>A container&lt;bool&gt;.  </em></span> The
Committee made provision for the space savings possible with that
(N/8) usage previously mentioned, so that you don't have to do
wasteful things like <code class="code">Container&lt;char&gt;</code> or
<code class="code">Container&lt;short int&gt;</code>. Specifically,
<code class="code">vector&lt;bool&gt;</code> is required to be specialized for
that space savings.
</p><p>
The problem is that <code class="code">vector&lt;bool&gt;</code> doesn't
behave like a normal vector anymore. There have been
journal articles which discuss the problems (the ones by Herb
Sutter in the May and July/August 1999 issues of C++ Report cover
it well). Future revisions of the ISO C++ Standard will change
the requirement for <code class="code">vector&lt;bool&gt;</code>
specialization. In the meantime, <code class="code">deque&lt;bool&gt;</code>
is recommended (although its behavior is sane, you probably will
not get the space savings, but the allocation scheme is different
than that of vector).
</p><p>
<span class="emphasis"><em>Extremely weird solutions.  </em></span> If
you have access to the compiler and linker at runtime, you can do
something insane, like figuring out just how many bits you need,
then writing a temporary source code file. That file contains an
instantiation of <code class="code">bitset</code> for the required number of
bits, inside some wrapper functions with unchanging signatures.
Have your program then call the compiler on that file using
Position Independent Code, then open the newly-created object
file and load those wrapper functions. You'll have an
instantiation of <code class="code">bitset&lt;N&gt;</code> for the exact
<code class="code">N</code> that you need at the time. Don't forget to delete
the temporary files. (Yes, this <span class="emphasis"><em>can</em></span> be, and
<span class="emphasis"><em>has been</em></span>, done.)
</p><p>
This would be the approach of either a visionary genius or a
raving lunatic, depending on your programming and management
style. Probably the latter.
</p><p>
Which of the above techniques you use, if any, are up to you and
your intended application. Some time/space profiling is
indicated if it really matters (don't just guess). And, if you
manage to do anything along the lines of the third category, the
author would love to hear from you...
</p><p>
Also note that the implementation of bitset used in libstdc++ has
<a class="link" href="bk01pt12ch34s02.html" title="HP/SGI">some extensions</a>.
</p></div><div class="sect2" title="Type String"><div class="titlepage"><div><div><h3 class="title"><a id="associative.bitset.type_string"></a>Type String</h3></div></div></div><p>
</p><p>
Bitmasks do not take char* nor const char* arguments in their
constructors. This is something of an accident, but you can read
about the problem: follow the library's <span class="quote"><span class="quote">Links</span></span> from
the homepage, and from the C++ information <span class="quote"><span class="quote">defect
reflector</span></span> link, select the library issues list. Issue
number 116 describes the problem.
</p><p>
For now you can simply make a temporary string object using the
constructor expression:
</p><pre class="programlisting">
std::bitset&lt;5&gt; b ( std::string(<span class="quote"><span class="quote">10110</span></span>) );
</pre><p>
instead of
</p><pre class="programlisting">
std::bitset&lt;5&gt; b ( <span class="quote"><span class="quote">10110</span></span> ); // invalid
</pre></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="associative.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="associative.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="containers_and_c.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 17. Associative </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 18. Interacting with C</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Index</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library" /><link rel="prev" href="appendix_gfdl.html" title="Appendix E. GNU Free Documentation License" /><link rel="next" href="../bk02.html" title="" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Index</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="appendix_gfdl.html">Prev</a> </td><th width="60%" align="center">The GNU C++ Library</th><td width="20%" align="right"> <a accesskey="n" href="../bk02.html">Next</a></td></tr></table><hr /></div><div class="index" title="Index"><div class="titlepage"><div><div><h2 class="title"><a id="id649926"></a>Index</h2></div></div></div><div class="index"><div class="indexdiv"><h3>A</h3><dl><dt>Algorithms, <a class="indexterm" href="algorithms.html">
Algorithms
</a></dt><dt>Appendix</dt><dd><dl><dt>Contributing, <a class="indexterm" href="appendix_contributing.html">
Contributing
</a></dt><dt>Free Documentation, <a class="indexterm" href="appendix_free.html">
Free Software Needs Free Documentation
</a></dt><dt>Porting and Maintenance, <a class="indexterm" href="appendix_porting.html">
Porting and Maintenance
</a></dt></dl></dd></dl></div><div class="indexdiv"><h3>C</h3><dl><dt>Containers, <a class="indexterm" href="containers.html">
Containers
</a></dt></dl></div><div class="indexdiv"><h3>D</h3><dl><dt>Diagnostics, <a class="indexterm" href="diagnostics.html">
Diagnostics
</a></dt></dl></div><div class="indexdiv"><h3>E</h3><dl><dt>Extensions, <a class="indexterm" href="extensions.html">
Extensions
</a></dt></dl></div><div class="indexdiv"><h3>I</h3><dl><dt>Input and Output, <a class="indexterm" href="io.html">
Input and Output
</a></dt><dt>Introduction, <a class="indexterm" href="intro.html">
Introduction
</a></dt><dt>Iterators, <a class="indexterm" href="iterators.html">
Iterators
</a></dt></dl></div><div class="indexdiv"><h3>L</h3><dl><dt>Localization, <a class="indexterm" href="localization.html">
Localization
</a></dt></dl></div><div class="indexdiv"><h3>N</h3><dl><dt>Numerics, <a class="indexterm" href="numerics.html">
Numerics
</a></dt></dl></div><div class="indexdiv"><h3>S</h3><dl><dt>Strings, <a class="indexterm" href="strings.html">
Strings
</a></dt><dt>Support, <a class="indexterm" href="support.html">
Support
</a></dt></dl></div><div class="indexdiv"><h3>T</h3><dl><dt>Test</dt><dd><dl><dt>Exception Safety, <a class="indexterm" href="test.html#test.exception.safety">
Qualifying Exception Safety Guarantees
</a></dt></dl></dd></dl></div><div class="indexdiv"><h3>U</h3><dl><dt>Utilities, <a class="indexterm" href="utilities.html">
Utilities
</a></dt></dl></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="appendix_gfdl.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="../bk02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix E. GNU Free Documentation License </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Part II.  Standard Contents</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library" /><link rel="prev" href="debug.html" title="Debugging Support" /><link rel="next" href="support.html" title="Chapter 4.  Support" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Part II. 
Standard Contents
</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="debug.html">Prev</a> </td><th width="60%" align="center">The GNU C++ Library</th><td width="20%" align="right"> <a accesskey="n" href="support.html">Next</a></td></tr></table><hr /></div><div class="part" title="Part II.  Standard Contents"><div class="titlepage"><div><div><h1 class="title"><a id="manual.std"></a>Part II. 
Standard Contents
</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="chapter"><a href="support.html">4.
Support
</a></span></dt><dd><dl><dt><span class="sect1"><a href="support.html#std.support.types">Types</a></span></dt><dd><dl><dt><span class="sect2"><a href="support.html#std.support.types.fundamental">Fundamental Types</a></span></dt><dt><span class="sect2"><a href="support.html#std.support.types.numeric_limits">Numeric Properties</a></span></dt><dt><span class="sect2"><a href="support.html#std.support.types.null">NULL</a></span></dt></dl></dd><dt><span class="sect1"><a href="dynamic_memory.html">Dynamic Memory</a></span></dt><dt><span class="sect1"><a href="termination.html">Termination</a></span></dt><dd><dl><dt><span class="sect2"><a href="termination.html#support.termination.handlers">Termination Handlers</a></span></dt><dt><span class="sect2"><a href="termination.html#support.termination.verbose">Verbose Terminate Handler</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="diagnostics.html">5.
Diagnostics
</a></span></dt><dd><dl><dt><span class="sect1"><a href="diagnostics.html#std.diagnostics.exceptions">Exceptions</a></span></dt><dd><dl><dt><span class="sect2"><a href="diagnostics.html#std.diagnostics.exceptions.api">API Reference</a></span></dt><dt><span class="sect2"><a href="diagnostics.html#std.diagnostics.exceptions.data">Adding Data to <code class="classname">exception</code></a></span></dt></dl></dd><dt><span class="sect1"><a href="bk01pt02ch05s02.html">Concept Checking</a></span></dt></dl></dd><dt><span class="chapter"><a href="utilities.html">6.
Utilities
</a></span></dt><dd><dl><dt><span class="section"><a href="utilities.html#std.util.functors">Functors</a></span></dt><dt><span class="section"><a href="pairs.html">Pairs</a></span></dt><dt><span class="section"><a href="memory.html">Memory</a></span></dt><dd><dl><dt><span class="section"><a href="memory.html#std.util.memory.allocator">Allocators</a></span></dt><dt><span class="section"><a href="memory.html#std.util.memory.auto_ptr">auto_ptr</a></span></dt><dt><span class="section"><a href="memory.html#std.util.memory.shared_ptr">shared_ptr</a></span></dt></dl></dd><dt><span class="section"><a href="traits.html">Traits</a></span></dt></dl></dd><dt><span class="chapter"><a href="strings.html">7.
Strings
</a></span></dt><dd><dl><dt><span class="sect1"><a href="strings.html#std.strings.string">String Classes</a></span></dt><dd><dl><dt><span class="sect2"><a href="strings.html#strings.string.simple">Simple Transformations</a></span></dt><dt><span class="sect2"><a href="strings.html#strings.string.case">Case Sensitivity</a></span></dt><dt><span class="sect2"><a href="strings.html#strings.string.character_types">Arbitrary Character Types</a></span></dt><dt><span class="sect2"><a href="strings.html#strings.string.token">Tokenizing</a></span></dt><dt><span class="sect2"><a href="strings.html#strings.string.shrink">Shrink to Fit</a></span></dt><dt><span class="sect2"><a href="strings.html#strings.string.Cstring">CString (MFC)</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="localization.html">8.
Localization
</a></span></dt><dd><dl><dt><span class="section"><a href="localization.html#std.localization.locales">Locales</a></span></dt><dd><dl><dt><span class="section"><a href="localization.html#std.localization.locales.locale">locale</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html">Facets</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#std.localization.facet.ctype">ctype</a></span></dt><dt><span class="section"><a href="facets.html#std.localization.facet.codecvt">codecvt</a></span></dt><dt><span class="section"><a href="facets.html#manual.localization.facet.messages">messages</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="containers.html">9.
Containers
</a></span></dt><dd><dl><dt><span class="sect1"><a href="containers.html#std.containers.sequences">Sequences</a></span></dt><dd><dl><dt><span class="sect2"><a href="containers.html#containers.sequences.list">list</a></span></dt><dt><span class="sect2"><a href="containers.html#containers.sequences.vector">vector</a></span></dt></dl></dd><dt><span class="sect1"><a href="associative.html">Associative</a></span></dt><dd><dl><dt><span class="sect2"><a href="associative.html#containers.associative.insert_hints">Insertion Hints</a></span></dt><dt><span class="sect2"><a href="associative.html#containers.associative.bitset">bitset</a></span></dt></dl></dd><dt><span class="sect1"><a href="containers_and_c.html">Interacting with C</a></span></dt><dd><dl><dt><span class="sect2"><a href="containers_and_c.html#containers.c.vs_array">Containers vs. Arrays</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="iterators.html">10.
Iterators
</a></span></dt><dd><dl><dt><span class="sect1"><a href="iterators.html#std.iterators.predefined">Predefined</a></span></dt><dd><dl><dt><span class="sect2"><a href="iterators.html#iterators.predefined.vs_pointers">Iterators vs. Pointers</a></span></dt><dt><span class="sect2"><a href="iterators.html#iterators.predefined.end">One Past the End</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="algorithms.html">11.
Algorithms
</a></span></dt><dd><dl><dt><span class="sect1"><a href="algorithms.html#std.algorithms.mutating">Mutating</a></span></dt><dd><dl><dt><span class="sect2"><a href="algorithms.html#algorithms.mutating.swap"><code class="function">swap</code></a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="numerics.html">12.
Numerics
</a></span></dt><dd><dl><dt><span class="sect1"><a href="numerics.html#std.numerics.complex">Complex</a></span></dt><dd><dl><dt><span class="sect2"><a href="numerics.html#numerics.complex.processing">complex Processing</a></span></dt></dl></dd><dt><span class="sect1"><a href="generalized_numeric_operations.html">Generalized Operations</a></span></dt><dt><span class="sect1"><a href="numerics_and_c.html">Interacting with C</a></span></dt><dd><dl><dt><span class="sect2"><a href="numerics_and_c.html#numerics.c.array">Numerics vs. Arrays</a></span></dt><dt><span class="sect2"><a href="numerics_and_c.html#numerics.c.c99">C99</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="io.html">13.
Input and Output
</a></span></dt><dd><dl><dt><span class="sect1"><a href="io.html#std.io.objects">Iostream Objects</a></span></dt><dt><span class="sect1"><a href="streambufs.html">Stream Buffers</a></span></dt><dd><dl><dt><span class="sect2"><a href="streambufs.html#io.streambuf.derived">Derived streambuf Classes</a></span></dt><dt><span class="sect2"><a href="streambufs.html#io.streambuf.buffering">Buffering</a></span></dt></dl></dd><dt><span class="sect1"><a href="stringstreams.html">Memory Based Streams</a></span></dt><dd><dl><dt><span class="sect2"><a href="stringstreams.html#std.io.memstreams.compat">Compatibility With strstream</a></span></dt></dl></dd><dt><span class="sect1"><a href="fstreams.html">File Based Streams</a></span></dt><dd><dl><dt><span class="sect2"><a href="fstreams.html#std.io.filestreams.copying_a_file">Copying a File</a></span></dt><dt><span class="sect2"><a href="fstreams.html#std.io.filestreams.binary">Binary Input and Output</a></span></dt></dl></dd><dt><span class="sect1"><a href="io_and_c.html">Interacting with C</a></span></dt><dd><dl><dt><span class="sect2"><a href="io_and_c.html#std.io.c.FILE">Using FILE* and file descriptors</a></span></dt><dt><span class="sect2"><a href="io_and_c.html#std.io.c.sync">Performance</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="atomics.html">14.
Atomics
</a></span></dt><dd><dl><dt><span class="sect1"><a href="atomics.html#std.atomics.api">API Reference</a></span></dt></dl></dd><dt><span class="chapter"><a href="concurrency.html">15.
Concurrency
</a></span></dt><dd><dl><dt><span class="sect1"><a href="concurrency.html#std.concurrency.api">API Reference</a></span></dt></dl></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="debug.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="support.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Debugging Support </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 4. 
Support
</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Numeric Properties</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="fundamental_types.html" title="Chapter 4. Types" /><link rel="prev" href="fundamental_types.html" title="Chapter 4. Types" /><link rel="next" href="bk01pt02ch04s03.html" title="NULL" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Numeric Properties</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="fundamental_types.html">Prev</a> </td><th width="60%" align="center">Chapter 4. Types</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt02ch04s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Numeric Properties"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.support.types.numeric_limits"></a>Numeric Properties</h2></div></div></div><p>
The header <code class="filename">limits</code> defines
traits classes to give access to various implementation
defined-aspects of the fundamental types. The traits classes --
fourteen in total -- are all specializations of the template class
<code class="classname">numeric_limits</code>, documented <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00593.html" target="_top">here</a>
and defined as follows:
</p><pre class="programlisting">
template&lt;typename T&gt;
struct class
{
static const bool is_specialized;
static T max() throw();
static T min() throw();
static const int digits;
static const int digits10;
static const bool is_signed;
static const bool is_integer;
static const bool is_exact;
static const int radix;
static T epsilon() throw();
static T round_error() throw();
static const int min_exponent;
static const int min_exponent10;
static const int max_exponent;
static const int max_exponent10;
static const bool has_infinity;
static const bool has_quiet_NaN;
static const bool has_signaling_NaN;
static const float_denorm_style has_denorm;
static const bool has_denorm_loss;
static T infinity() throw();
static T quiet_NaN() throw();
static T denorm_min() throw();
static const bool is_iec559;
static const bool is_bounded;
static const bool is_modulo;
static const bool traps;
static const bool tinyness_before;
static const float_round_style round_style;
};
</pre></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="fundamental_types.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="fundamental_types.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt02ch04s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 4. Types </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> NULL</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>NULL</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="fundamental_types.html" title="Chapter 4. Types" /><link rel="prev" href="bk01pt02ch04s02.html" title="Numeric Properties" /><link rel="next" href="dynamic_memory.html" title="Chapter 5. Dynamic Memory" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">NULL</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt02ch04s02.html">Prev</a> </td><th width="60%" align="center">Chapter 4. Types</th><td width="20%" align="right"> <a accesskey="n" href="dynamic_memory.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="NULL"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.support.types.null"></a>NULL</h2></div></div></div><p>
The only change that might affect people is the type of
<code class="constant">NULL</code>: while it is required to be a macro,
the definition of that macro is <span class="emphasis"><em>not</em></span> allowed
to be <code class="constant">(void*)0</code>, which is often used in C.
</p><p>
For <span class="command"><strong>g++</strong></span>, <code class="constant">NULL</code> is
</p><pre class="programlisting">#define</pre><p>'d to be
<code class="constant">__null</code>, a magic keyword extension of
<span class="command"><strong>g++</strong></span>.
</p><p>
The biggest problem of #defining <code class="constant">NULL</code> to be
something like <span class="quote"><span class="quote">0L</span></span> is that the compiler will view
that as a long integer before it views it as a pointer, so
overloading won't do what you expect. (This is why
<span class="command"><strong>g++</strong></span> has a magic extension, so that
<code class="constant">NULL</code> is always a pointer.)
</p><p>In his book <a class="ulink" href="http://www.awprofessional.com/titles/0-201-92488-9/" target="_top"><span class="emphasis"><em>Effective
C++</em></span></a>, Scott Meyers points out that the best way
to solve this problem is to not overload on pointer-vs-integer
types to begin with. He also offers a way to make your own magic
<code class="constant">NULL</code> that will match pointers before it
matches integers.
</p><p>See
<a class="ulink" href="http://www.awprofessional.com/titles/0-201-31015-5/" target="_top">the
Effective C++ CD example</a>
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt02ch04s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="fundamental_types.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="dynamic_memory.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Numeric Properties </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 5. Dynamic Memory</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 8. Concept Checking</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="diagnostics.html" title="Part III.  Diagnostics" /><link rel="prev" href="bk01pt03ch07s02.html" title="Adding Data to Exceptions" /><link rel="next" href="utilities.html" title="Part IV.  Utilities" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 8. Concept Checking</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt03ch07s02.html">Prev</a> </td><th width="60%" align="center">Part III
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Concept Checking</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="diagnostics.html" title="Chapter 5.  Diagnostics" /><link rel="prev" href="diagnostics.html" title="Chapter 5.  Diagnostics" /><link rel="next" href="utilities.html" title="Chapter 6.  Utilities" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Concept Checking</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="diagnostics.html">Prev</a> </td><th width="60%" align="center">Chapter 5
Diagnostics
</th><td width="20%" align="right"> <a accesskey="n" href="utilities.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 8. Concept Checking"><div class="titlepage"><div><div><h2 class="title"><a id="manual.diagnostics.concept_checking"></a>Chapter 8. Concept Checking</h2></div></div></div><p>
</th><td width="20%" align="right"> <a accesskey="n" href="utilities.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Concept Checking"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.diagnostics.concept_checking"></a>Concept Checking</h2></div></div></div><p>
In 1999, SGI added <span class="quote"><span class="quote">concept checkers</span></span> to their
implementation of the STL: code which checked the template
parameters of instantiated pieces of the STL, in order to insure
......@@ -39,7 +39,10 @@
support for template parameter constraints based on concepts in the core
language. This will obviate the need for the library-simulated concept
checking described above.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt03ch07s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="diagnostics.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="utilities.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Adding Data to Exceptions </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part IV. 
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Diagnostics
 </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 6. 
Utilities
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Support
</th><td width="20%" align="right"> <a accesskey="n" href="fundamental_types.html">Next</a></td></tr></table><hr /></div><div class="preface"><div class="titlepage"><div><div><h2 class="title"><a id="id616146"></a></h2></div></div></div><p>
This part deals with the functions called and objects created
automatically during the course of a program's existence.
</p><p>
While we can't reproduce the contents of the Standard here (you
need to get your own copy from your nation's member body; see our
homepage for help), we can mention a couple of changes in what
kind of support a C++ program gets from the Standard Library.
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 </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 4. Types</td></tr></table></div></body></html>
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The standard exception classes carry with them a single string as
data (usually describing what went wrong or where the 'throw' took
place). It's good to remember that you can add your own data to
these exceptions when extending the hierarchy:
</p><pre class="programlisting">
struct My_Exception : public std::runtime_error
{
public:
My_Exception (const string&amp; whatarg)
: std::runtime_error(whatarg), e(errno), id(GetDataBaseID()) { }
int errno_at_time_of_throw() const { return e; }
DBID id_of_thing_that_threw() const { return id; }
protected:
int e;
DBID id; // some user-defined type
};
</pre></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="exceptions.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="exceptions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch08.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 7. Exceptions </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 8. Concept Checking</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Semantics</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; debug&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="debug_mode.html" title="Chapter 30. Debug Mode" /><link rel="prev" href="debug_mode.html" title="Chapter 30. Debug Mode" /><link rel="next" href="bk01pt12ch30s03.html" title="Using" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Semantics</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="debug_mode.html">Prev</a> </td><th width="60%" align="center">Chapter 30. Debug Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch30s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Semantics"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.debug_mode.semantics"></a>Semantics</h2></div></div></div><p>
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Semantics</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; debug&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="debug_mode.html" title="Chapter 17. Debug Mode" /><link rel="prev" href="debug_mode.html" title="Chapter 17. Debug Mode" /><link rel="next" href="bk01pt03ch17s03.html" title="Using" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Semantics</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="debug_mode.html">Prev</a> </td><th width="60%" align="center">Chapter 17. Debug Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch17s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Semantics"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.debug_mode.semantics"></a>Semantics</h2></div></div></div><p>
</p><p>A program that uses the C++ standard library correctly
will maintain the same semantics under debug mode as it had with
the normal (release) library. All functional and exception-handling
......@@ -10,7 +10,7 @@
instance, erasing an element in a <code class="code">std::list</code> is a
constant-time operation in normal library, but in debug mode it is
linear in the number of iterators that reference that particular
list. So while your (correct) program won't change its results, it
list. So while your (correct) program won't change its results, it
is likely to execute more slowly.</p><p>libstdc++ includes many extensions to the C++ standard library. In
some cases the extensions are obvious, such as the hashed
associative containers, whereas other extensions give predictable
......@@ -52,4 +52,4 @@ with the debug-mode checks included, but this is unsupported and not
guaranteed to work. For full debug-mode support you can use the
<code class="code">__gnu_debug::basic_string</code> debugging container directly,
which always works correctly.
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</p><div class="sect2" title="Using the Debug Mode"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.using.mode"></a>Using the Debug Mode</h3></div></div></div><p>To use the libstdc++ debug mode, compile your application with the
compiler flag <code class="code">-D_GLIBCXX_DEBUG</code>. Note that this flag
changes the sizes and behavior of standard class templates such
as <code class="code">std::vector</code>, and therefore you can only link code
compiled with debug mode and code compiled without debug mode if no
instantiation of a container is passed between the two translation
units.</p><p>By default, error messages are formatted to fit on lines of about
78 characters. The environment variable
<code class="code">GLIBCXX_DEBUG_MESSAGE_LENGTH</code> can be used to request a
different length.</p></div><div class="sect2" title="Using a Specific Debug Container"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.using.specific"></a>Using a Specific Debug Container</h3></div></div></div><p>When it is not feasible to recompile your entire application, or
only specific containers need checking, debugging containers are
available as GNU extensions. These debugging containers are
functionally equivalent to the standard drop-in containers used in
debug mode, but they are available in a separate namespace as GNU
extensions and may be used in programs compiled with either release
mode or with debug mode. The
following table provides the names and headers of the debugging
containers:
</p><div class="table"><a id="id487304"></a><p class="title"><b>Table 17.1. Debugging Containers</b></p><div class="table-contents"><table summary="Debugging Containers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Container</th><th align="left">Header</th><th align="left">Debug container</th><th align="left">Debug header</th></tr></thead><tbody><tr><td align="left"><code class="classname">std::bitset</code></td><td align="left"><code class="filename">bitset</code></td><td align="left"><code class="classname">__gnu_debug::bitset</code></td><td align="left"><code class="filename">&lt;debug/bitset&gt;</code></td></tr><tr><td align="left"><code class="classname">std::deque</code></td><td align="left"><code class="filename">deque</code></td><td align="left"><code class="classname">__gnu_debug::deque</code></td><td align="left"><code class="filename">&lt;debug/deque&gt;</code></td></tr><tr><td align="left"><code class="classname">std::list</code></td><td align="left"><code class="filename">list</code></td><td align="left"><code class="classname">__gnu_debug::list</code></td><td align="left"><code class="filename">&lt;debug/list&gt;</code></td></tr><tr><td align="left"><code class="classname">std::map</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="classname">__gnu_debug::map</code></td><td align="left"><code class="filename">&lt;debug/map&gt;</code></td></tr><tr><td align="left"><code class="classname">std::multimap</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="classname">__gnu_debug::multimap</code></td><td align="left"><code class="filename">&lt;debug/map&gt;</code></td></tr><tr><td align="left"><code class="classname">std::multiset</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="classname">__gnu_debug::multiset</code></td><td align="left"><code class="filename">&lt;debug/set&gt;</code></td></tr><tr><td align="left"><code class="classname">std::set</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="classname">__gnu_debug::set</code></td><td align="left"><code class="filename">&lt;debug/set&gt;</code></td></tr><tr><td align="left"><code class="classname">std::string</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="classname">__gnu_debug::string</code></td><td align="left"><code class="filename">&lt;debug/string&gt;</code></td></tr><tr><td align="left"><code class="classname">std::wstring</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="classname">__gnu_debug::wstring</code></td><td align="left"><code class="filename">&lt;debug/string&gt;</code></td></tr><tr><td align="left"><code class="classname">std::basic_string</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="classname">__gnu_debug::basic_string</code></td><td align="left"><code class="filename">&lt;debug/string&gt;</code></td></tr><tr><td align="left"><code class="classname">std::vector</code></td><td align="left"><code class="filename">vector</code></td><td align="left"><code class="classname">__gnu_debug::vector</code></td><td align="left"><code class="filename">&lt;debug/vector&gt;</code></td></tr></tbody></table></div></div><br class="table-break" /><p>In addition, when compiling in C++0x mode, these additional
containers have additional debug capability.
</p><div class="table"><a id="id488498"></a><p class="title"><b>Table 17.2. Debugging Containers C++0x</b></p><div class="table-contents"><table summary="Debugging Containers C++0x" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Container</th><th align="left">Header</th><th align="left">Debug container</th><th align="left">Debug header</th></tr></thead><tbody><tr><td align="left"><code class="classname">std::unordered_map</code></td><td align="left"><code class="filename">unordered_map</code></td><td align="left"><code class="classname">__gnu_debug::unordered_map</code></td><td align="left"><code class="filename">&lt;debug/unordered_map&gt;</code></td></tr><tr><td align="left"><code class="classname">std::unordered_multimap</code></td><td align="left"><code class="filename">unordered_map</code></td><td align="left"><code class="classname">__gnu_debug::unordered_multimap</code></td><td align="left"><code class="filename">&lt;debug/unordered_map&gt;</code></td></tr><tr><td align="left"><code class="classname">std::unordered_set</code></td><td align="left"><code class="filename">unordered_set</code></td><td align="left"><code class="classname">__gnu_debug::unordered_set</code></td><td align="left"><code class="filename">&lt;debug/unordered_set&gt;</code></td></tr><tr><td align="left"><code class="classname">std::unordered_multiset</code></td><td align="left"><code class="filename">unordered_set</code></td><td align="left"><code class="classname">__gnu_debug::unordered_multiset</code></td><td align="left"><code class="filename">&lt;debug/unordered_set&gt;</code></td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt03ch17s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="debug_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch17s04.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Semantics </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Design</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Semantics</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; parallel&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="parallel_mode.html" title="Chapter 31. Parallel Mode" /><link rel="prev" href="parallel_mode.html" title="Chapter 31. Parallel Mode" /><link rel="next" href="bk01pt12ch31s03.html" title="Using" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Semantics</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="parallel_mode.html">Prev</a> </td><th width="60%" align="center">Chapter 31. Parallel Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch31s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Semantics"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.parallel_mode.semantics"></a>Semantics</h2></div></div></div><p> The parallel mode STL algorithms are currently not exception-safe,
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Semantics</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; parallel&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="parallel_mode.html" title="Chapter 18. Parallel Mode" /><link rel="prev" href="parallel_mode.html" title="Chapter 18. Parallel Mode" /><link rel="next" href="bk01pt03ch18s03.html" title="Using" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Semantics</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="parallel_mode.html">Prev</a> </td><th width="60%" align="center">Chapter 18. Parallel Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch18s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Semantics"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.parallel_mode.semantics"></a>Semantics</h2></div></div></div><p> The parallel mode STL algorithms are currently not exception-safe,
i.e. user-defined functors must not throw exceptions.
Also, the order of execution is not guaranteed for some functions, of course.
Therefore, user-defined functors should not have any concurrent side effects.
......@@ -8,4 +8,4 @@ Therefore, user-defined functors should not have any concurrent side effects.
OpenMP parallel regions in concurrent threads,
it is not possible to call parallel STL algorithm in
concurrent threads, either.
It might work with other compilers, though.</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="parallel_mode.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="parallel_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch31s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 31. Parallel Mode </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Using</td></tr></table></div></body></html>
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</p><div class="sect2" title="Interface Basics"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.design.intro"></a>Interface Basics</h3></div></div></div><p>
All parallel algorithms are intended to have signatures that are
equivalent to the ISO C++ algorithms replaced. For instance, the
......@@ -105,7 +105,7 @@ For the following algorithms in general, we have
<code class="code">__gnu_parallel::parallel_tag</code> and
<code class="code">__gnu_parallel::default_parallel_tag</code>, in addition to
<code class="code">__gnu_parallel::sequential_tag</code>.
<code class="code">__gnu_parallel::default_parallel_tag</code> chooses the default
<code class="code">__gnu_parallel::default_parallel_tag</code> chooses the default
algorithm at compiletime, as does omitting the tag.
<code class="code">__gnu_parallel::parallel_tag</code> postpones the decision to runtime
(see next section).
......@@ -120,7 +120,7 @@ Exact and sampling are the two available splitting strategies.
For the <code class="code">sort</code> and <code class="code">stable_sort</code> algorithms, there are
several additional choices, namely
<code class="code">__gnu_parallel::multiway_mergesort_tag</code>,
<code class="code">__gnu_parallel::multiway_mergesort_exact_tag</code>,
<code class="code">__gnu_parallel::multiway_mergesort_exact_tag</code>,
<code class="code">__gnu_parallel::multiway_mergesort_sampling_tag</code>,
<code class="code">__gnu_parallel::quicksort_tag</code>, and
<code class="code">__gnu_parallel::balanced_quicksort_tag</code>.
......@@ -198,7 +198,7 @@ int main()
explicitly sequential:
<code class="code">__gnu_serial</code>.
</p><p> Two namespaces contain the parallel mode:
<code class="code">std::__parallel</code> and <code class="code">__gnu_parallel</code>.
<code class="code">std::__parallel</code> and <code class="code">__gnu_parallel</code>.
</p><p> Parallel implementations of standard components, including
template helpers to select parallelism, are defined in <code class="code">namespace
std::__parallel</code>. For instance, <code class="function">std::transform</code> from <code class="filename">algorithm</code> has a parallel counterpart in
......@@ -210,4 +210,4 @@ __gnu_parallel</code>.
</p><p> More information, and an organized index of types and functions
related to the parallel mode on a per-namespace basis, can be found in
the generated source documentation.
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Both the normal conformance and regression tests and the
supplemental performance tests work.
</p><p>
</p><p>
To run the conformance and regression tests with the parallel mode
active,
</p><pre class="screen">
......@@ -11,7 +11,7 @@
</pre><p>
The log and summary files for conformance testing are in the
<code class="filename">testsuite/parallel</code> directory.
</p><p>
</p><p>
To run the performance tests with the parallel mode active,
</p><pre class="screen">
<strong class="userinput"><code>make check-performance-parallel</code></strong>
......@@ -23,4 +23,4 @@
additional software dependencies than the usual bare-boned text
file, and can be generated by using the <code class="code">make
doc-performance</code> rule in the testsuite's Makefile.
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Many large projects use their own data structures instead of the ones in the
standard library. If these data structures are similar in functionality
to the standard library, they can be instrumented with the same hooks
that are used to instrument the standard library.
The instrumentation API is exposed in file
<code class="code">profiler.h</code> (look for "Instrumentation hooks").
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Empirical Cost Model</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; profile&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="profile_mode.html" title="Chapter 19. Profile Mode" /><link rel="prev" href="bk01pt03ch19s03.html" title="Extensions for Custom Containers" /><link rel="next" href="bk01pt03ch19s05.html" title="Implementation Issues" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Empirical Cost Model</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt03ch19s03.html">Prev</a> </td><th width="60%" align="center">Chapter 19. Profile Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch19s05.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Empirical Cost Model"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.profile_mode.cost_model"></a>Empirical Cost Model</h2></div></div></div><p>
Currently, the cost model uses formulas with predefined relative weights
for alternative containers or container implementations. For instance,
iterating through a vector is X times faster than iterating through a list.
......@@ -15,4 +15,4 @@
filled in either by hand or by an automated training mechanism.
The analysis module will then use this database instead of the built in.
generic parameters.
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Accurate stack traces are needed during profiling since we group events by
call context and dynamic instance. Without accurate traces, diagnostics
may be hard to interpret. For instance, when giving advice to the user
......@@ -24,15 +24,15 @@
During profiling, we keep a single information table per diagnostic.
There is a single lock per information table.
</p></div><div class="sect2" title="Using the Standard Library in the Instrumentation Implementation"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.profile_mode.implementation.stdlib-in-proflib"></a>Using the Standard Library in the Instrumentation Implementation</h3></div></div></div><p>
As much as we would like to avoid uses of stdlibc++ within our
instrumentation library, containers such as unordered_map are very
appealing. We plan to use them as long as they are named properly
As much as we would like to avoid uses of libstdc++ within our
instrumentation library, containers such as unordered_map are very
appealing. We plan to use them as long as they are named properly
to avoid ambiguity.
</p></div><div class="sect2" title="Malloc Hooks"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.profile_mode.implementation.malloc-hooks"></a>Malloc Hooks</h3></div></div></div><p>
User applications/libraries can provide malloc hooks.
When the implementation of the malloc hooks uses stdlibc++, there can
be an infinite cycle between the profile mode instrumentation and the
the malloc hook code.
malloc hook code.
</p><p>
We protect against reentrance to the profile mode instrumentation code,
which should avoid this problem in most cases.
......@@ -46,6 +46,6 @@
The profiling library state is initialized at the first call to a profiling
method. This allows us to record the construction of all global objects.
However, we cannot do the same at destruction time. The trace is written
by a function registered by <code class="code">atexit</code>, thus invoked by
by a function registered by <code class="code">atexit</code>, thus invoked by
<code class="code">exit</code>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch32s04.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="profile_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch32s06.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Empirical Cost Model </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Developer Information</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Developer Information</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; profile&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="profile_mode.html" title="Chapter 32. Profile Mode" /><link rel="prev" href="bk01pt12ch32s05.html" title="Implementation Issues" /><link rel="next" href="bk01pt12ch32s07.html" title="Diagnostics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Developer Information</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt12ch32s05.html">Prev</a> </td><th width="60%" align="center">Chapter 32. Profile Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch32s07.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Developer Information"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.profile_mode.developer"></a>Developer Information</h2></div></div></div><div class="sect2" title="Big Picture"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.profile_mode.developer.bigpic"></a>Big Picture</h3></div></div></div><p>The profile mode headers are included with
<code class="code">-D_GLIBCXX_PROFILE</code> through preprocessor directives in
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Developer Information</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; C++&#10; , &#10; library&#10; , &#10; profile&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="profile_mode.html" title="Chapter 19. Profile Mode" /><link rel="prev" href="bk01pt03ch19s05.html" title="Implementation Issues" /><link rel="next" href="bk01pt03ch19s07.html" title="Diagnostics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Developer Information</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt03ch19s05.html">Prev</a> </td><th width="60%" align="center">Chapter 19. Profile Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch19s07.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Developer Information"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.profile_mode.developer"></a>Developer Information</h2></div></div></div><div class="sect2" title="Big Picture"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.profile_mode.developer.bigpic"></a>Big Picture</h3></div></div></div><p>The profile mode headers are included with
<code class="code">-D_GLIBCXX_PROFILE</code> through preprocessor directives in
<code class="code">include/std/*</code>.
</p><p>Instrumented implementations are provided in
</p><p>Instrumented implementations are provided in
<code class="code">include/profile/*</code>. All instrumentation hooks are macros
defined in <code class="code">include/profile/profiler.h</code>.
</p><p>All the implementation of the instrumentation hooks is in
</p><p>All the implementation of the instrumentation hooks is in
<code class="code">include/profile/impl/*</code>. Although all the code gets included,
thus is publicly visible, only a small number of functions are called from
outside this directory. All calls to hook implementations must be
done through macros defined in <code class="code">profiler.h</code>. The macro
must ensure (1) that the call is guarded against reentrance and
must ensure (1) that the call is guarded against reentrance and
(2) that the call can be turned off at compile time using a
<code class="code">-D_GLIBCXX_PROFILE_...</code> compiler option.
</p></div><div class="sect2" title="How To Add A Diagnostic"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.profile_mode.developer.howto"></a>How To Add A Diagnostic</h3></div></div></div><p>Let's say the diagnostic name is "magic".
</p><p>If you need to instrument a header not already under
</p><p>If you need to instrument a header not already under
<code class="code">include/profile/*</code>, first edit the corresponding header
under <code class="code">include/std/</code> and add a preprocessor directive such
as the one in <code class="code">include/std/vector</code>:
......@@ -57,7 +57,7 @@
Define class <code class="code">__magic_stack_info: public __magic_info</code>.
This defines the content of a line in the stack table.
</p></li><li class="listitem"><p>
Define class <code class="code">__trace_magic: public __trace_base&lt;__magic_info,
Define class <code class="code">__trace_magic: public __trace_base&lt;__magic_info,
__magic_stack_info&gt;</code>.
It defines the content of the trace associated with this diagnostic.
</p></li></ul></div><p>
......@@ -65,4 +65,4 @@
<code class="code">include/profile/impl/profiler_trace.h</code>. Use
<code class="code">__trace_vector_to_list</code> as an example.
</p><p>Add documentation in file <code class="code">doc/xml/manual/profile_mode.xml</code>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch32s05.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="profile_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch32s07.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Implementation Issues </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Diagnostics</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>HP/SGI</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_containers.html" title="Chapter 34. Containers" /><link rel="prev" href="ext_containers.html" title="Chapter 34. Containers" /><link rel="next" href="bk01pt12ch34s03.html" title="Deprecated HP/SGI" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">HP/SGI</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_containers.html">Prev</a> </td><th width="60%" align="center">Chapter 34. Containers</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch34s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="HP/SGI"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.containers.sgi"></a>HP/SGI</h2></div></div></div><p>
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</p><p>A few extensions and nods to backwards-compatibility have been made with
containers. Those dealing with older SGI-style allocators are dealt with
elsewhere. The remaining ones all deal with bits:
......@@ -26,7 +26,7 @@
</pre><p>Note that these may in fact be removed in the future, although we have
no present plans to do so (and there doesn't seem to be any immediate
reason to).
</p><p>The semantics of member function <code class="code">operator[]</code> are not specified
</p><p>The semantics of member function <code class="code">operator[]</code> are not specified
in the C++ standard. A long-standing defect report calls for sensible
obvious semantics, which are already implemented here: <code class="code">op[]</code>
on a const bitset returns a bool, and for a non-const bitset returns a
......@@ -40,4 +40,4 @@
</p><pre class="programlisting">
size_t _Find_first() const;
size_t _Find_next (size_t prev) const;</pre><p>The same caveat given for the _Unchecked_* functions applies here also.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_containers.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_containers.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch34s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 34. Containers </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Deprecated HP/SGI</td></tr></table></div></body></html>
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The SGI hashing classes <code class="classname">hash_set</code> and
<code class="classname">hash_set</code> have been deprecated by the
unordered_set, unordered_multiset, unordered_map,
......@@ -47,4 +47,4 @@
possibility of pathological cases, you'll probably get better
performance from hash_map.
</em></span>
</p></blockquote></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch34s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_containers.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_utilities.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">HP/SGI </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 35. Utilities</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Implementation</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_concurrency.html" title="Chapter 41. Concurrency" /><link rel="prev" href="ext_concurrency.html" title="Chapter 41. Concurrency" /><link rel="next" href="bk01pt12ch41s03.html" title="Use" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Implementation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_concurrency.html">Prev</a> </td><th width="60%" align="center">Chapter 41. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch41s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Implementation"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.impl"></a>Implementation</h2></div></div></div><div class="sect2" title="Using Builtin Atomic Functions"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.impl.atomic_fallbacks"></a>Using Builtin Atomic Functions</h3></div></div></div><p>The functions for atomic operations described above are either
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Implementation</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="prev" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="next" href="bk01pt03ch28s03.html" title="Use" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Implementation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_concurrency.html">Prev</a> </td><th width="60%" align="center">Chapter 28. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch28s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Implementation"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.impl"></a>Implementation</h2></div></div></div><div class="sect2" title="Using Builtin Atomic Functions"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.impl.atomic_fallbacks"></a>Using Builtin Atomic Functions</h3></div></div></div><p>The functions for atomic operations described above are either
implemented via compiler intrinsics (if the underlying host is
capable) or by library fallbacks.</p><p>Compiler intrinsics (builtins) are always preferred. However, as
the compiler builtins for atomics are not universally implemented,
......@@ -12,7 +12,7 @@ missing reference to <code class="code">__sync_fetch_and_add_4</code>.)
conditionally, via the <code class="code">-march</code> command line flag. This makes
usage vary depending on the target hardware and the flags used during
compile.
</p><p>
</p><p>
If builtins are possible for bool-sized integral types,
<code class="code">_GLIBCXX_ATOMIC_BUILTINS_1</code> will be defined.
If builtins are possible for int-sized integral types,
......@@ -38,4 +38,4 @@ use this layer. More detail as to the specific interface can be found in the sou
functions, and usage found in the usual &lt;pthread.h&gt; file,
including <code class="code">pthread_t</code>, <code class="code">pthread_once_t</code>, <code class="code">pthread_create</code>,
etc.
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Use</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_concurrency.html" title="Chapter 41. Concurrency" /><link rel="prev" href="bk01pt12ch41s02.html" title="Implementation" /><link rel="next" href="appendix_contributing.html" title="Appendix A.  Contributing" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Use</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt12ch41s02.html">Prev</a> </td><th width="60%" align="center">Chapter 41. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="appendix_contributing.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Use"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.use"></a>Use</h2></div></div></div><p>Typical usage of the last two constructs is demonstrated as follows:
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Use</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="prev" href="bk01pt03ch28s02.html" title="Implementation" /><link rel="next" href="bk01pt04.html" title="Part IV.  Appendices" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Use</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt03ch28s02.html">Prev</a> </td><th width="60%" align="center">Chapter 28. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt04.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Use"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.use"></a>Use</h2></div></div></div><p>Typical usage of the last two constructs is demonstrated as follows:
</p><pre class="programlisting">
#include &lt;ext/concurrence.h&gt;
......@@ -31,7 +31,6 @@ the mutex as control moves out of this block.
concurrence-related errors. These classes
are: <code class="code">__concurrence_lock_error</code>, <code class="code">__concurrence_unlock_error</code>, <code class="code">__concurrence_wait_error</code>,
and <code class="code">__concurrence_broadcast_error</code>.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch41s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix_contributing.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Implementation </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix A. 
Contributing
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt03ch28s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt04.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Implementation </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part IV. 
Appendices
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Extensions
</th><td width="20%" align="right"> <a accesskey="n" href="ext_compile_checks.html">Next</a></td></tr></table><hr /></div><div class="preface"><div class="titlepage"><div><div><h2 class="title"><a id="id684983"></a></h2></div></div></div><p>
</th><td width="20%" align="right"> <a accesskey="n" href="ext_compile_checks.html">Next</a></td></tr></table><hr /></div><div class="preface"><div class="titlepage"><div><div><h2 class="title"><a id="id433082"></a></h2></div></div></div><p>
Here we will make an attempt at describing the non-Standard extensions to
the library. Some of these are from SGI's STL, some of these are GNU's,
and some just seemed to appear on the doorstep.
</p><p><span class="emphasis"><em>Before</em></span> you leap in and use any of these
extensions, be aware of two things:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
Non-Standard means exactly that.
Non-Standard means exactly that.
</p><p>
The behavior, and the very
existence, of these extensions may change with little or no
warning. (Ideally, the really good ones will appear in the next
revision of C++.) Also, other platforms, other compilers, other
versions of g++ or libstdc++ may not recognize these names, or
treat them differently, or...
treat them differently, or...
</p></li><li class="listitem"><p>
You should know how to access these headers properly.
</p></li></ol></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="extensions.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_compile_checks.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part XII. 
You should know how to access these headers properly.
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Extensions
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 </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 16. Compile Time Checks</td></tr></table></div></body></html>
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Appendices
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Appendices
</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="appendix"><a href="appendix_contributing.html">A.
Contributing
</a></span></dt><dd><dl><dt><span class="sect1"><a href="appendix_contributing.html#contrib.list">Contributor Checklist</a></span></dt><dd><dl><dt><span class="sect2"><a href="appendix_contributing.html#list.reading">Reading</a></span></dt><dt><span class="sect2"><a href="appendix_contributing.html#list.copyright">Assignment</a></span></dt><dt><span class="sect2"><a href="appendix_contributing.html#list.getting">Getting Sources</a></span></dt><dt><span class="sect2"><a href="appendix_contributing.html#list.patches">Submitting Patches</a></span></dt></dl></dd><dt><span class="sect1"><a href="source_organization.html">Directory Layout and Source Conventions</a></span></dt><dt><span class="sect1"><a href="source_code_style.html">Coding Style</a></span></dt><dd><dl><dt><span class="sect2"><a href="source_code_style.html#coding_style.bad_identifiers">Bad Identifiers</a></span></dt><dt><span class="sect2"><a href="source_code_style.html#coding_style.example">By Example</a></span></dt></dl></dd><dt><span class="sect1"><a href="documentation_style.html">Documentation Style</a></span></dt><dd><dl><dt><span class="sect2"><a href="documentation_style.html#doc_style.doxygen">Doxygen</a></span></dt><dt><span class="sect2"><a href="documentation_style.html#doc_style.docbook">Docbook</a></span></dt><dt><span class="sect2"><a href="documentation_style.html#doc_style.combines">Combines</a></span></dt></dl></dd><dt><span class="sect1"><a href="source_design_notes.html">Design Notes</a></span></dt></dl></dd><dt><span class="appendix"><a href="appendix_porting.html">B.
Porting and Maintenance
</a></span></dt><dd><dl><dt><span class="sect1"><a href="appendix_porting.html#appendix.porting.build_hacking">Configure and Build Hacking</a></span></dt><dd><dl><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.prereq">Prerequisites</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.map">Overview: What Comes from Where</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.scripts">Storing Information in non-AC files (like configure.host)</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.conventions">Coding and Commenting Conventions</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.acinclude">The acinclude.m4 layout</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.enable"><code class="constant">GLIBCXX_ENABLE</code>, the <code class="literal">--enable</code> maker</a></span></dt></dl></dd><dt><span class="sect1"><a href="internals.html">Porting to New Hardware or Operating Systems</a></span></dt><dd><dl><dt><span class="sect2"><a href="internals.html#internals.os">Operating System</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.cpu">CPU</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.char_types">Character Types</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.thread_safety">Thread Safety</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.numeric_limits">Numeric Limits</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.libtool">Libtool</a></span></dt></dl></dd><dt><span class="sect1"><a href="test.html">Test</a></span></dt><dd><dl><dt><span class="sect2"><a href="test.html#test.organization">Organization</a></span></dt><dt><span class="sect2"><a href="test.html#test.run">Running the Testsuite</a></span></dt><dt><span class="sect2"><a href="test.html#test.new_tests">Writing a new test case</a></span></dt><dt><span class="sect2"><a href="test.html#test.harness">Test Harness and Utilities</a></span></dt><dt><span class="sect2"><a href="test.html#test.special">Special Topics</a></span></dt></dl></dd><dt><span class="sect1"><a href="abi.html">ABI Policy and Guidelines</a></span></dt><dd><dl><dt><span class="sect2"><a href="abi.html#abi.cxx_interface">The C++ Interface</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.versioning">Versioning</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.changes_allowed">Allowed Changes</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.changes_no">Prohibited Changes</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.testing">Testing</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.issues">Outstanding Issues</a></span></dt></dl></dd><dt><span class="sect1"><a href="api.html">API Evolution and Deprecation History</a></span></dt><dd><dl><dt><span class="sect2"><a href="api.html#api.rel_300"><code class="constant">3.0</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_310"><code class="constant">3.1</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_320"><code class="constant">3.2</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_330"><code class="constant">3.3</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_340"><code class="constant">3.4</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_400"><code class="constant">4.0</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_410"><code class="constant">4.1</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_420"><code class="constant">4.2</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_430"><code class="constant">4.3</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_440"><code class="constant">4.4</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_450"><code class="constant">4.5</code></a></span></dt></dl></dd><dt><span class="sect1"><a href="backwards.html">Backwards Compatibility</a></span></dt><dd><dl><dt><span class="sect2"><a href="backwards.html#backwards.first">First</a></span></dt><dt><span class="sect2"><a href="backwards.html#backwards.second">Second</a></span></dt><dt><span class="sect2"><a href="backwards.html#backwards.third">Third</a></span></dt></dl></dd></dl></dd><dt><span class="appendix"><a href="appendix_free.html">C.
Free Software Needs Free Documentation
</a></span></dt><dt><span class="appendix"><a href="appendix_gpl.html">D.
<acronym class="acronym">GNU</acronym> General Public License version 3
</a></span></dt><dt><span class="appendix"><a href="appendix_gfdl.html">E. GNU Free Documentation License</a></span></dt></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt03ch28s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="spine.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix_contributing.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Use </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix A. 
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Strings
</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt05ch13s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 13. String Classes"><div class="titlepage"><div><div><h2 class="title"><a id="manual.strings.string"></a>Chapter 13. String Classes</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="bk01pt05ch13.html#strings.string.simple">Simple Transformations</a></span></dt><dt><span class="sect1"><a href="bk01pt05ch13s02.html">Case Sensitivity</a></span></dt><dt><span class="sect1"><a href="bk01pt05ch13s03.html">Arbitrary Character Types</a></span></dt><dt><span class="sect1"><a href="bk01pt05ch13s04.html">Tokenizing</a></span></dt><dt><span class="sect1"><a href="bk01pt05ch13s05.html">Shrink to Fit</a></span></dt><dt><span class="sect1"><a href="bk01pt05ch13s06.html">CString (MFC)</a></span></dt></dl></div><div class="sect1" title="Simple Transformations"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="strings.string.simple"></a>Simple Transformations</h2></div></div></div><p>
Here are Standard, simple, and portable ways to perform common
transformations on a <code class="code">string</code> instance, such as
"convert to all upper case." The word transformations
is especially apt, because the standard template function
<code class="code">transform&lt;&gt;</code> is used.
</p><p>
This code will go through some iterations. Here's a simple
version:
</p><pre class="programlisting">
#include &lt;string&gt;
#include &lt;algorithm&gt;
#include &lt;cctype&gt; // old &lt;ctype.h&gt;
struct ToLower
{
char operator() (char c) const { return std::tolower(c); }
};
struct ToUpper
{
char operator() (char c) const { return std::toupper(c); }
};
int main()
{
std::string s ("Some Kind Of Initial Input Goes Here");
// Change everything into upper case
std::transform (s.begin(), s.end(), s.begin(), ToUpper());
// Change everything into lower case
std::transform (s.begin(), s.end(), s.begin(), ToLower());
// Change everything back into upper case, but store the
// result in a different string
std::string capital_s;
capital_s.resize(s.size());
std::transform (s.begin(), s.end(), capital_s.begin(), ToUpper());
}
</pre><p>
<span class="emphasis"><em>Note</em></span> that these calls all
involve the global C locale through the use of the C functions
<code class="code">toupper/tolower</code>. This is absolutely guaranteed to work --
but <span class="emphasis"><em>only</em></span> if the string contains <span class="emphasis"><em>only</em></span> characters
from the basic source character set, and there are <span class="emphasis"><em>only</em></span>
96 of those. Which means that not even all English text can be
represented (certain British spellings, proper names, and so forth).
So, if all your input forevermore consists of only those 96
characters (hahahahahaha), then you're done.
</p><p><span class="emphasis"><em>Note</em></span> that the
<code class="code">ToUpper</code> and <code class="code">ToLower</code> function objects
are needed because <code class="code">toupper</code> and <code class="code">tolower</code>
are overloaded names (declared in <code class="code">&lt;cctype&gt;</code> and
<code class="code">&lt;locale&gt;</code>) so the template-arguments for
<code class="code">transform&lt;&gt;</code> cannot be deduced, as explained in
<a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-11/msg00180.html" target="_top">this
message</a>.
At minimum, you can write short wrappers like
</p><pre class="programlisting">
char toLower (char c)
{
return std::tolower(c);
} </pre><p>(Thanks to James Kanze for assistance and suggestions on all of this.)
</p><p>Another common operation is trimming off excess whitespace. Much
like transformations, this task is trivial with the use of string's
<code class="code">find</code> family. These examples are broken into multiple
statements for readability:
</p><pre class="programlisting">
std::string str (" \t blah blah blah \n ");
// trim leading whitespace
string::size_type notwhite = str.find_first_not_of(" \t\n");
str.erase(0,notwhite);
// trim trailing whitespace
notwhite = str.find_last_not_of(" \t\n");
str.erase(notwhite+1); </pre><p>Obviously, the calls to <code class="code">find</code> could be inserted directly
into the calls to <code class="code">erase</code>, in case your compiler does not
optimize named temporaries out of existence.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="strings.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="strings.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt05ch13s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part V. 
Strings
 </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Case Sensitivity</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Case Sensitivity</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt05ch13.html" title="Chapter 13. String Classes" /><link rel="prev" href="bk01pt05ch13.html" title="Chapter 13. String Classes" /><link rel="next" href="bk01pt05ch13s03.html" title="Arbitrary Character Types" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Case Sensitivity</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt05ch13.html">Prev</a> </td><th width="60%" align="center">Chapter 13. String Classes</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt05ch13s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Case Sensitivity"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="strings.string.case"></a>Case Sensitivity</h2></div></div></div><p>
</p><p>The well-known-and-if-it-isn't-well-known-it-ought-to-be
<a class="ulink" href="http://www.gotw.ca/gotw/" target="_top">Guru of the Week</a>
discussions held on Usenet covered this topic in January of 1998.
Briefly, the challenge was, <span class="quote"><span class="quote">write a 'ci_string' class which
is identical to the standard 'string' class, but is
case-insensitive in the same way as the (common but nonstandard)
C function stricmp()</span></span>.
</p><pre class="programlisting">
ci_string s( "AbCdE" );
// case insensitive
assert( s == "abcde" );
assert( s == "ABCDE" );
// still case-preserving, of course
assert( strcmp( s.c_str(), "AbCdE" ) == 0 );
assert( strcmp( s.c_str(), "abcde" ) != 0 ); </pre><p>The solution is surprisingly easy. The original answer was
posted on Usenet, and a revised version appears in Herb Sutter's
book <span class="emphasis"><em>Exceptional C++</em></span> and on his website as <a class="ulink" href="http://www.gotw.ca/gotw/029.htm" target="_top">GotW 29</a>.
</p><p>See? Told you it was easy!</p><p>
<span class="emphasis"><em>Added June 2000:</em></span> The May 2000 issue of C++
Report contains a fascinating <a class="ulink" href="http://lafstern.org/matt/col2_new.pdf" target="_top"> article</a> by
Matt Austern (yes, <span class="emphasis"><em>the</em></span> Matt Austern) on why
case-insensitive comparisons are not as easy as they seem, and
why creating a class is the <span class="emphasis"><em>wrong</em></span> way to go
about it in production code. (The GotW answer mentions one of
the principle difficulties; his article mentions more.)
</p><p>Basically, this is "easy" only if you ignore some things,
things which may be too important to your program to ignore. (I chose
to ignore them when originally writing this entry, and am surprised
that nobody ever called me on it...) The GotW question and answer
remain useful instructional tools, however.
</p><p><span class="emphasis"><em>Added September 2000:</em></span> James Kanze provided a link to a
<a class="ulink" href="http://www.unicode.org/reports/tr21/tr21-5.html" target="_top">Unicode
Technical Report discussing case handling</a>, which provides some
very good information.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt05ch13.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt05ch13.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt05ch13s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 13. String Classes </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Arbitrary Character Types</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Arbitrary Character Types</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt05ch13.html" title="Chapter 13. String Classes" /><link rel="prev" href="bk01pt05ch13s02.html" title="Case Sensitivity" /><link rel="next" href="bk01pt05ch13s04.html" title="Tokenizing" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Arbitrary Character Types</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt05ch13s02.html">Prev</a> </td><th width="60%" align="center">Chapter 13. String Classes</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt05ch13s04.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Arbitrary Character Types"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="strings.string.character_types"></a>Arbitrary Character Types</h2></div></div></div><p>
</p><p>The <code class="code">std::basic_string</code> is tantalizingly general, in that
it is parameterized on the type of the characters which it holds.
In theory, you could whip up a Unicode character class and instantiate
<code class="code">std::basic_string&lt;my_unicode_char&gt;</code>, or assuming
that integers are wider than characters on your platform, maybe just
declare variables of type <code class="code">std::basic_string&lt;int&gt;</code>.
</p><p>That's the theory. Remember however that basic_string has additional
type parameters, which take default arguments based on the character
type (called <code class="code">CharT</code> here):
</p><pre class="programlisting">
template &lt;typename CharT,
typename Traits = char_traits&lt;CharT&gt;,
typename Alloc = allocator&lt;CharT&gt; &gt;
class basic_string { .... };</pre><p>Now, <code class="code">allocator&lt;CharT&gt;</code> will probably Do The Right
Thing by default, unless you need to implement your own allocator
for your characters.
</p><p>But <code class="code">char_traits</code> takes more work. The char_traits
template is <span class="emphasis"><em>declared</em></span> but not <span class="emphasis"><em>defined</em></span>.
That means there is only
</p><pre class="programlisting">
template &lt;typename CharT&gt;
struct char_traits
{
static void foo (type1 x, type2 y);
...
};</pre><p>and functions such as char_traits&lt;CharT&gt;::foo() are not
actually defined anywhere for the general case. The C++ standard
permits this, because writing such a definition to fit all possible
CharT's cannot be done.
</p><p>The C++ standard also requires that char_traits be specialized for
instantiations of <code class="code">char</code> and <code class="code">wchar_t</code>, and it
is these template specializations that permit entities like
<code class="code">basic_string&lt;char,char_traits&lt;char&gt;&gt;</code> to work.
</p><p>If you want to use character types other than char and wchar_t,
such as <code class="code">unsigned char</code> and <code class="code">int</code>, you will
need suitable specializations for them. For a time, in earlier
versions of GCC, there was a mostly-correct implementation that
let programmers be lazy but it broke under many situations, so it
was removed. GCC 3.4 introduced a new implementation that mostly
works and can be specialized even for <code class="code">int</code> and other
built-in types.
</p><p>If you want to use your own special character class, then you have
<a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-08/msg00163.html" target="_top">a lot
of work to do</a>, especially if you with to use i18n features
(facets require traits information but don't have a traits argument).
</p><p>Another example of how to specialize char_traits was given <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-08/msg00260.html" target="_top">on the
mailing list</a> and at a later date was put into the file <code class="code">
include/ext/pod_char_traits.h</code>. We agree
that the way it's used with basic_string (scroll down to main())
doesn't look nice, but that's because <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-08/msg00236.html" target="_top">the
nice-looking first attempt</a> turned out to <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-08/msg00242.html" target="_top">not
be conforming C++</a>, due to the rule that CharT must be a POD.
(See how tricky this is?)
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</p><p>The Standard C (and C++) function <code class="code">strtok()</code> leaves a lot to
be desired in terms of user-friendliness. It's unintuitive, it
destroys the character string on which it operates, and it requires
you to handle all the memory problems. But it does let the client
code decide what to use to break the string into pieces; it allows
you to choose the "whitespace," so to speak.
</p><p>A C++ implementation lets us keep the good things and fix those
annoyances. The implementation here is more intuitive (you only
call it once, not in a loop with varying argument), it does not
affect the original string at all, and all the memory allocation
is handled for you.
</p><p>It's called stringtok, and it's a template function. Sources are
as below, in a less-portable form than it could be, to keep this
example simple (for example, see the comments on what kind of
string it will accept).
</p><pre class="programlisting">
#include &lt;string&gt;
template &lt;typename Container&gt;
void
stringtok(Container &amp;container, string const &amp;in,
const char * const delimiters = " \t\n")
{
const string::size_type len = in.length();
string::size_type i = 0;
while (i &lt; len)
{
// Eat leading whitespace
i = in.find_first_not_of(delimiters, i);
if (i == string::npos)
return; // Nothing left but white space
// Find the end of the token
string::size_type j = in.find_first_of(delimiters, i);
// Push token
if (j == string::npos)
{
container.push_back(in.substr(i));
return;
}
else
container.push_back(in.substr(i, j-i));
// Set up for next loop
i = j + 1;
}
}
</pre><p>
The author uses a more general (but less readable) form of it for
parsing command strings and the like. If you compiled and ran this
code using it:
</p><pre class="programlisting">
std::list&lt;string&gt; ls;
stringtok (ls, " this \t is\t\n a test ");
for (std::list&lt;string&gt;const_iterator i = ls.begin();
i != ls.end(); ++i)
{
std::cerr &lt;&lt; ':' &lt;&lt; (*i) &lt;&lt; ":\n";
} </pre><p>You would see this as output:
</p><pre class="programlisting">
:this:
:is:
:a:
:test: </pre><p>with all the whitespace removed. The original <code class="code">s</code> is still
available for use, <code class="code">ls</code> will clean up after itself, and
<code class="code">ls.size()</code> will return how many tokens there were.
</p><p>As always, there is a price paid here, in that stringtok is not
as fast as strtok. The other benefits usually outweigh that, however.
</p><p><span class="emphasis"><em>Added February 2001:</em></span> Mark Wilden pointed out that the
standard <code class="code">std::getline()</code> function can be used with standard
<code class="code">istringstreams</code> to perform
tokenizing as well. Build an istringstream from the input text,
and then use std::getline with varying delimiters (the three-argument
signature) to extract tokens into a string.
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</p><p>From GCC 3.4 calling <code class="code">s.reserve(res)</code> on a
<code class="code">string s</code> with <code class="code">res &lt; s.capacity()</code> will
reduce the string's capacity to <code class="code">std::max(s.size(), res)</code>.
</p><p>This behaviour is suggested, but not required by the standard. Prior
to GCC 3.4 the following alternative can be used instead
</p><pre class="programlisting">
std::string(str.data(), str.size()).swap(str);
</pre><p>This is similar to the idiom for reducing
a <code class="code">vector</code>'s memory usage
(see <a class="link" href="../faq.html#faq.size_equals_capacity" title="7.8.">this FAQ
entry</a>) but the regular copy constructor cannot be used
because libstdc++'s <code class="code">string</code> is Copy-On-Write.
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</p><p>A common lament seen in various newsgroups deals with the Standard
string class as opposed to the Microsoft Foundation Class called
CString. Often programmers realize that a standard portable
answer is better than a proprietary nonportable one, but in porting
their application from a Win32 platform, they discover that they
are relying on special functions offered by the CString class.
</p><p>Things are not as bad as they seem. In
<a class="ulink" href="http://gcc.gnu.org/ml/gcc/1999-04n/msg00236.html" target="_top">this
message</a>, Joe Buck points out a few very important things:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The Standard <code class="code">string</code> supports all the operations
that CString does, with three exceptions.
</p></li><li class="listitem"><p>Two of those exceptions (whitespace trimming and case
conversion) are trivial to implement. In fact, we do so
on this page.
</p></li><li class="listitem"><p>The third is <code class="code">CString::Format</code>, which allows formatting
in the style of <code class="code">sprintf</code>. This deserves some mention:
</p></li></ul></div><p>
The old libg++ library had a function called form(), which did much
the same thing. But for a Standard solution, you should use the
stringstream classes. These are the bridge between the iostream
hierarchy and the string class, and they operate with regular
streams seamlessly because they inherit from the iostream
hierarchy. An quick example:
</p><pre class="programlisting">
#include &lt;iostream&gt;
#include &lt;string&gt;
#include &lt;sstream&gt;
string f (string&amp; incoming) // incoming is "foo N"
{
istringstream incoming_stream(incoming);
string the_word;
int the_number;
incoming_stream &gt;&gt; the_word // extract "foo"
&gt;&gt; the_number; // extract N
ostringstream output_stream;
output_stream &lt;&lt; "The word was " &lt;&lt; the_word
&lt;&lt; " and 3*N was " &lt;&lt; (3*the_number);
return output_stream.str();
} </pre><p>A serious problem with CString is a design bug in its memory
allocation. Specifically, quoting from that same message:
</p><pre class="programlisting">
CString suffers from a common programming error that results in
poor performance. Consider the following code:
CString n_copies_of (const CString&amp; foo, unsigned n)
{
CString tmp;
for (unsigned i = 0; i &lt; n; i++)
tmp += foo;
return tmp;
}
This function is O(n^2), not O(n). The reason is that each +=
causes a reallocation and copy of the existing string. Microsoft
applications are full of this kind of thing (quadratic performance
on tasks that can be done in linear time) -- on the other hand,
we should be thankful, as it's created such a big market for high-end
ix86 hardware. :-)
If you replace CString with string in the above function, the
performance is O(n).
</pre><p>Joe Buck also pointed out some other things to keep in mind when
comparing CString and the Standard string class:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>CString permits access to its internal representation; coders
who exploited that may have problems moving to <code class="code">string</code>.
</p></li><li class="listitem"><p>Microsoft ships the source to CString (in the files
MFC\SRC\Str{core,ex}.cpp), so you could fix the allocation
bug and rebuild your MFC libraries.
<span class="emphasis"><em><span class="emphasis"><em>Note:</em></span> It looks like the CString shipped
with VC++6.0 has fixed this, although it may in fact have been
one of the VC++ SPs that did it.</em></span>
</p></li><li class="listitem"><p><code class="code">string</code> operations like this have O(n) complexity
<span class="emphasis"><em>if the implementors do it correctly</em></span>. The libstdc++
implementors did it correctly. Other vendors might not.
</p></li><li class="listitem"><p>While parts of the SGI STL are used in libstdc++, their
string class is not. The SGI <code class="code">string</code> is essentially
<code class="code">vector&lt;char&gt;</code> and does not do any reference
counting like libstdc++'s does. (It is O(n), though.)
So if you're thinking about SGI's string or rope classes,
you're now looking at four possibilities: CString, the
libstdc++ string, the SGI string, and the SGI rope, and this
is all before any allocator or traits customizations! (More
choices than you can shake a stick at -- want fries with that?)
</p></li></ul></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt05ch13s05.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt05ch13.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="localization.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Shrink to Fit </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part VI. 
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 19. Predefined</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="iterators.html" title="Part VIII.  Iterators" /><link rel="prev" href="iterators.html" title="Part VIII.  Iterators" /><link rel="next" href="bk01pt08ch19s02.html" title="One Past the End" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 19. Predefined</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="iterators.html">Prev</a> </td><th width="60%" align="center">Part VIII. 
Iterators
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The following
FAQ <a class="link" href="../faq.html#faq.iterator_as_pod" title="7.1.">entry</a> points out that
iterators are not implemented as pointers. They are a generalization
of pointers, but they are implemented in libstdc++ as separate
classes.
</p><p>Keeping that simple fact in mind as you design your code will
prevent a whole lot of difficult-to-understand bugs.
</p><p>You can think of it the other way 'round, even. Since iterators
are a generalization, that means that <span class="emphasis"><em>pointers</em></span> are
<span class="emphasis"><em>iterators</em></span>, and that pointers can be used whenever an
iterator would be. All those functions in the Algorithms chapter
of the Standard will work just as well on plain arrays and their
pointers.
</p><p>That doesn't mean that when you pass in a pointer, it gets wrapped
into some special delegating iterator-to-pointer class with a layer
of overhead. (If you think that's the case anywhere, you don't
understand templates to begin with...) Oh, no; if you pass
in a pointer, then the compiler will instantiate that template
using T* as a type, and good old high-speed pointer arithmetic as
its operations, so the resulting code will be doing exactly the same
things as it would be doing if you had hand-coded it yourself (for
the 273rd time).
</p><p>How much overhead <span class="emphasis"><em>is</em></span> there when using an iterator class?
Very little. Most of the layering classes contain nothing but
typedefs, and typedefs are "meta-information" that simply
tell the compiler some nicknames; they don't create code. That
information gets passed down through inheritance, so while the
compiler has to do work looking up all the names, your runtime code
does not. (This has been a prime concern from the beginning.)
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="iterators.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="iterators.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt08ch19s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part VIII. 
Iterators
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>One Past the End</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt08ch19.html" title="Chapter 19. Predefined" /><link rel="prev" href="bk01pt08ch19.html" title="Chapter 19. Predefined" /><link rel="next" href="algorithms.html" title="Part IX.  Algorithms" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">One Past the End</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt08ch19.html">Prev</a> </td><th width="60%" align="center">Chapter 19. Predefined</th><td width="20%" align="right"> <a accesskey="n" href="algorithms.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="One Past the End"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="iterators.predefined.end"></a>One Past the End</h2></div></div></div><p>This starts off sounding complicated, but is actually very easy,
especially towards the end. Trust me.
</p><p>Beginners usually have a little trouble understand the whole
'past-the-end' thing, until they remember their early algebra classes
(see, they <span class="emphasis"><em>told</em></span> you that stuff would come in handy!) and
the concept of half-open ranges.
</p><p>First, some history, and a reminder of some of the funkier rules in
C and C++ for builtin arrays. The following rules have always been
true for both languages:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>You can point anywhere in the array, <span class="emphasis"><em>or to the first element
past the end of the array</em></span>. A pointer that points to one
past the end of the array is guaranteed to be as unique as a
pointer to somewhere inside the array, so that you can compare
such pointers safely.
</p></li><li class="listitem"><p>You can only dereference a pointer that points into an array.
If your array pointer points outside the array -- even to just
one past the end -- and you dereference it, Bad Things happen.
</p></li><li class="listitem"><p>Strictly speaking, simply pointing anywhere else invokes
undefined behavior. Most programs won't puke until such a
pointer is actually dereferenced, but the standards leave that
up to the platform.
</p></li></ol></div><p>The reason this past-the-end addressing was allowed is to make it
easy to write a loop to go over an entire array, e.g.,
while (*d++ = *s++);.
</p><p>So, when you think of two pointers delimiting an array, don't think
of them as indexing 0 through n-1. Think of them as <span class="emphasis"><em>boundary
markers</em></span>:
</p><pre class="programlisting">
beginning end
| |
| | This is bad. Always having to
| | remember to add or subtract one.
| | Off-by-one bugs very common here.
V V
array of N elements
|---|---|--...--|---|---|
| 0 | 1 | ... |N-2|N-1|
|---|---|--...--|---|---|
^ ^
| |
| | This is good. This is safe. This
| | is guaranteed to work. Just don't
| | dereference 'end'.
beginning end
</pre><p>See? Everything between the boundary markers is part of the array.
Simple.
</p><p>Now think back to your junior-high school algebra course, when you
were learning how to draw graphs. Remember that a graph terminating
with a solid dot meant, "Everything up through this point,"
and a graph terminating with an open dot meant, "Everything up
to, but not including, this point," respectively called closed
and open ranges? Remember how closed ranges were written with
brackets, <span class="emphasis"><em>[a,b]</em></span>, and open ranges were written with parentheses,
<span class="emphasis"><em>(a,b)</em></span>?
</p><p>The boundary markers for arrays describe a <span class="emphasis"><em>half-open range</em></span>,
starting with (and including) the first element, and ending with (but
not including) the last element: <span class="emphasis"><em>[beginning,end)</em></span>. See, I
told you it would be simple in the end.
</p><p>Iterators, and everything working with iterators, follows this same
time-honored tradition. A container's <code class="code">begin()</code> method returns
an iterator referring to the first element, and its <code class="code">end()</code>
method returns a past-the-end iterator, which is guaranteed to be
unique and comparable against any other iterator pointing into the
middle of the container.
</p><p>Container constructors, container methods, and algorithms, all take
pairs of iterators describing a range of values on which to operate.
All of these ranges are half-open ranges, so you pass the beginning
iterator as the starting parameter, and the one-past-the-end iterator
as the finishing parameter.
</p><p>This generalizes very well. You can operate on sub-ranges quite
easily this way; functions accepting a <span class="emphasis"><em>[first,last)</em></span> range
don't know or care whether they are the boundaries of an entire {array,
sequence, container, whatever}, or whether they only enclose a few
elements from the center. This approach also makes zero-length
sequences very simple to recognize: if the two endpoints compare
equal, then the {array, sequence, container, whatever} is empty.
</p><p>Just don't dereference <code class="code">end()</code>.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt08ch19.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt08ch19.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="algorithms.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 19. Predefined </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part IX. 
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 20. Mutating</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; , &#10; algorithm&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="algorithms.html" title="Part IX.  Algorithms" /><link rel="prev" href="bk01pt09pr02.html" title="" /><link rel="next" href="numerics.html" title="Part X.  Numerics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 20. Mutating</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt09pr02.html">Prev</a> </td><th width="60%" align="center">Part IX. 
Algorithms
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containers, then the call will automatically be replaced by a call to
<code class="code"> x.swap(y); </code> instead.
</p><p>This allows member functions of each container class to take over, and
containers' swap functions should have O(1) complexity according to
the standard. (And while "should" allows implementations to
behave otherwise and remain compliant, this implementation does in
fact use constant-time swaps.) This should not be surprising, since
for two containers of the same type to swap contents, only some
internal pointers to storage need to be exchanged.
</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt09pr02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="algorithms.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="numerics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"> </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part X. 
Numerics
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; , &#10; algorithm&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="algorithms.html" title="Part IX.  Algorithms" /><link rel="prev" href="algorithms.html" title="Part IX.  Algorithms" /><link rel="next" href="bk01pt09ch20.html" title="Chapter 20. Mutating" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="algorithms.html">Prev</a> </td><th width="60%" align="center">Part IX. 
Algorithms
</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt09ch20.html">Next</a></td></tr></table><hr /></div><div class="preface"><div class="titlepage"><div><div><h2 class="title"><a id="id638172"></a></h2></div></div></div><p>
The neatest accomplishment of the algorithms chapter is that all the
work is done via iterators, not containers directly. This means two
important things:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
Anything that behaves like an iterator can be used in one of
these algorithms. Raw pointers make great candidates, thus
built-in arrays are fine containers, as well as your own iterators.
</p></li><li class="listitem"><p>
The algorithms do not (and cannot) affect the container as a
whole; only the things between the two iterator endpoints. If
you pass a range of iterators only enclosing the middle third of
a container, then anything outside that range is inviolate.
</p></li></ol></div><p>
Even strings can be fed through the algorithms here, although the
string class has specialized versions of many of these functions
(for example, <code class="code">string::find()</code>). Most of the examples
on this page will use simple arrays of integers as a playground
for algorithms, just to keep things simple. The use of
<span class="emphasis"><em>N</em></span> as a size in the examples is to keep
things easy to read but probably won't be valid code. You can
use wrappers such as those described in the <a class="link" href="containers.html" title="Part VII.  Containers">containers chapter</a> to
keep real code readable.
</p><p>
The single thing that trips people up the most is the definition
of <span class="emphasis"><em>range</em></span> used with iterators; the famous
"past-the-end" rule that everybody loves to hate. The
<a class="link" href="iterators.html" title="Part VIII.  Iterators">iterators
chapter</a> of this document has a complete explanation of
this simple rule that seems to cause so much confusion. Once you
get <span class="emphasis"><em>range</em></span> into your head (it's not that
hard, honest!), then the algorithms are a cakewalk.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="algorithms.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="algorithms.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt09ch20.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part IX. 
Algorithms
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>C99</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="numerics_and_c.html" title="Chapter 23. Interacting with C" /><link rel="prev" href="numerics_and_c.html" title="Chapter 23. Interacting with C" /><link rel="next" href="io.html" title="Part XI.  Input and Output" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">C99</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="numerics_and_c.html">Prev</a> </td><th width="60%" align="center">Chapter 23. Interacting with C</th><td width="20%" align="right"> <a accesskey="n" href="io.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="C99"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="numerics.c.c99"></a>C99</h2></div></div></div><p>In addition to the other topics on this page, we'll note here some
of the C99 features that appear in libstdc++.
</p><p>The C99 features depend on the <code class="code">--enable-c99</code> configure flag.
This flag is already on by default, but it can be disabled by the
user. Also, the configuration machinery will disable it if the
necessary support for C99 (e.g., header files) cannot be found.
</p><p>As of GCC 3.0, C99 support includes classification functions
such as <code class="code">isnormal</code>, <code class="code">isgreater</code>,
<code class="code">isnan</code>, etc.
The functions used for 'long long' support such as <code class="code">strtoll</code>
are supported, as is the <code class="code">lldiv_t</code> typedef. Also supported
are the wide character functions using 'long long', like
<code class="code">wcstoll</code>.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="numerics_and_c.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="numerics_and_c.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="io.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 23. Interacting with C </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part XI. 
Input and Output
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Buffering</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="streambufs.html" title="Chapter 25. Stream Buffers" /><link rel="prev" href="streambufs.html" title="Chapter 25. Stream Buffers" /><link rel="next" href="stringstreams.html" title="Chapter 26. Memory Based Streams" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Buffering</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="streambufs.html">Prev</a> </td><th width="60%" align="center">Chapter 25. Stream Buffers</th><td width="20%" align="right"> <a accesskey="n" href="stringstreams.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Buffering"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="io.streambuf.buffering"></a>Buffering</h2></div></div></div><p>First, are you sure that you understand buffering? Particularly
the fact that C++ may not, in fact, have anything to do with it?
</p><p>The rules for buffering can be a little odd, but they aren't any
different from those of C. (Maybe that's why they can be a bit
odd.) Many people think that writing a newline to an output
stream automatically flushes the output buffer. This is true only
when the output stream is, in fact, a terminal and not a file
or some other device -- and <span class="emphasis"><em>that</em></span> may not even be true
since C++ says nothing about files nor terminals. All of that is
system-dependent. (The "newline-buffer-flushing only occurring
on terminals" thing is mostly true on Unix systems, though.)
</p><p>Some people also believe that sending <code class="code">endl</code> down an
output stream only writes a newline. This is incorrect; after a
newline is written, the buffer is also flushed. Perhaps this
is the effect you want when writing to a screen -- get the text
out as soon as possible, etc -- but the buffering is largely
wasted when doing this to a file:
</p><pre class="programlisting">
output &lt;&lt; "a line of text" &lt;&lt; endl;
output &lt;&lt; some_data_variable &lt;&lt; endl;
output &lt;&lt; "another line of text" &lt;&lt; endl; </pre><p>The proper thing to do in this case to just write the data out
and let the libraries and the system worry about the buffering.
If you need a newline, just write a newline:
</p><pre class="programlisting">
output &lt;&lt; "a line of text\n"
&lt;&lt; some_data_variable &lt;&lt; '\n'
&lt;&lt; "another line of text\n"; </pre><p>I have also joined the output statements into a single statement.
You could make the code prettier by moving the single newline to
the start of the quoted text on the last line, for example.
</p><p>If you do need to flush the buffer above, you can send an
<code class="code">endl</code> if you also need a newline, or just flush the buffer
yourself:
</p><pre class="programlisting">
output &lt;&lt; ...... &lt;&lt; flush; // can use std::flush manipulator
output.flush(); // or call a member fn </pre><p>On the other hand, there are times when writing to a file should
be like writing to standard error; no buffering should be done
because the data needs to appear quickly (a prime example is a
log file for security-related information). The way to do this is
just to turn off the buffering <span class="emphasis"><em>before any I/O operations at
all</em></span> have been done (note that opening counts as an I/O operation):
</p><pre class="programlisting">
std::ofstream os;
std::ifstream is;
int i;
os.rdbuf()-&gt;pubsetbuf(0,0);
is.rdbuf()-&gt;pubsetbuf(0,0);
os.open("/foo/bar/baz");
is.open("/qux/quux/quuux");
...
os &lt;&lt; "this data is written immediately\n";
is &gt;&gt; i; // and this will probably cause a disk read </pre><p>Since all aspects of buffering are handled by a streambuf-derived
member, it is necessary to get at that member with <code class="code">rdbuf()</code>.
Then the public version of <code class="code">setbuf</code> can be called. The
arguments are the same as those for the Standard C I/O Library
function (a buffer area followed by its size).
</p><p>A great deal of this is implementation-dependent. For example,
<code class="code">streambuf</code> does not specify any actions for its own
<code class="code">setbuf()</code>-ish functions; the classes derived from
<code class="code">streambuf</code> each define behavior that "makes
sense" for that class: an argument of (0,0) turns off buffering
for <code class="code">filebuf</code> but does nothing at all for its siblings
<code class="code">stringbuf</code> and <code class="code">strstreambuf</code>, and specifying
anything other than (0,0) has varying effects.
User-defined classes derived from <code class="code">streambuf</code> can
do whatever they want. (For <code class="code">filebuf</code> and arguments for
<code class="code">(p,s)</code> other than zeros, libstdc++ does what you'd expect:
the first <code class="code">s</code> bytes of <code class="code">p</code> are used as a buffer,
which you must allocate and deallocate.)
</p><p>A last reminder: there are usually more buffers involved than
just those at the language/library level. Kernel buffers, disk
buffers, and the like will also have an effect. Inspecting and
changing those are system-dependent.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="streambufs.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="streambufs.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="stringstreams.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 25. Stream Buffers </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 26. Memory Based Streams</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Binary Input and Output</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="fstreams.html" title="Chapter 27. File Based Streams" /><link rel="prev" href="fstreams.html" title="Chapter 27. File Based Streams" /><link rel="next" href="io_and_c.html" title="Chapter 28. Interacting with C" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Binary Input and Output</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="fstreams.html">Prev</a> </td><th width="60%" align="center">Chapter 27. File Based Streams</th><td width="20%" align="right"> <a accesskey="n" href="io_and_c.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Binary Input and Output"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.io.filestreams.binary"></a>Binary Input and Output</h2></div></div></div><p>
</p><p>The first and most important thing to remember about binary I/O is
that opening a file with <code class="code">ios::binary</code> is not, repeat
<span class="emphasis"><em>not</em></span>, the only thing you have to do. It is not a silver
bullet, and will not allow you to use the <code class="code">&lt;&lt;/&gt;&gt;</code>
operators of the normal fstreams to do binary I/O.
</p><p>Sorry. Them's the breaks.
</p><p>This isn't going to try and be a complete tutorial on reading and
writing binary files (because "binary"
covers a lot of ground), but we will try and clear
up a couple of misconceptions and common errors.
</p><p>First, <code class="code">ios::binary</code> has exactly one defined effect, no more
and no less. Normal text mode has to be concerned with the newline
characters, and the runtime system will translate between (for
example) '\n' and the appropriate end-of-line sequence (LF on Unix,
CRLF on DOS, CR on Macintosh, etc). (There are other things that
normal mode does, but that's the most obvious.) Opening a file in
binary mode disables this conversion, so reading a CRLF sequence
under Windows won't accidentally get mapped to a '\n' character, etc.
Binary mode is not supposed to suddenly give you a bitstream, and
if it is doing so in your program then you've discovered a bug in
your vendor's compiler (or some other part of the C++ implementation,
possibly the runtime system).
</p><p>Second, using <code class="code">&lt;&lt;</code> to write and <code class="code">&gt;&gt;</code> to
read isn't going to work with the standard file stream classes, even
if you use <code class="code">skipws</code> during reading. Why not? Because
ifstream and ofstream exist for the purpose of <span class="emphasis"><em>formatting</em></span>,
not reading and writing. Their job is to interpret the data into
text characters, and that's exactly what you don't want to happen
during binary I/O.
</p><p>Third, using the <code class="code">get()</code> and <code class="code">put()/write()</code> member
functions still aren't guaranteed to help you. These are
"unformatted" I/O functions, but still character-based.
(This may or may not be what you want, see below.)
</p><p>Notice how all the problems here are due to the inappropriate use
of <span class="emphasis"><em>formatting</em></span> functions and classes to perform something
which <span class="emphasis"><em>requires</em></span> that formatting not be done? There are a
seemingly infinite number of solutions, and a few are listed here:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="quote"><span class="quote">Derive your own fstream-type classes and write your own
&lt;&lt;/&gt;&gt; operators to do binary I/O on whatever data
types you're using.</span></span>
</p><p>
This is a Bad Thing, because while
the compiler would probably be just fine with it, other humans
are going to be confused. The overloaded bitshift operators
have a well-defined meaning (formatting), and this breaks it.
</p></li><li class="listitem"><p>
<span class="quote"><span class="quote">Build the file structure in memory, then
<code class="code">mmap()</code> the file and copy the
structure.
</span></span>
</p><p>
Well, this is easy to make work, and easy to break, and is
pretty equivalent to using <code class="code">::read()</code> and
<code class="code">::write()</code> directly, and makes no use of the
iostream library at all...
</p></li><li class="listitem"><p>
<span class="quote"><span class="quote">Use streambufs, that's what they're there for.</span></span>
</p><p>
While not trivial for the beginner, this is the best of all
solutions. The streambuf/filebuf layer is the layer that is
responsible for actual I/O. If you want to use the C++
library for binary I/O, this is where you start.
</p></li></ul></div><p>How to go about using streambufs is a bit beyond the scope of this
document (at least for now), but while streambufs go a long way,
they still leave a couple of things up to you, the programmer.
As an example, byte ordering is completely between you and the
operating system, and you have to handle it yourself.
</p><p>Deriving a streambuf or filebuf
class from the standard ones, one that is specific to your data
types (or an abstraction thereof) is probably a good idea, and
lots of examples exist in journals and on Usenet. Using the
standard filebufs directly (either by declaring your own or by
using the pointer returned from an fstream's <code class="code">rdbuf()</code>)
is certainly feasible as well.
</p><p>One area that causes problems is trying to do bit-by-bit operations
with filebufs. C++ is no different from C in this respect: I/O
must be done at the byte level. If you're trying to read or write
a few bits at a time, you're going about it the wrong way. You
must read/write an integral number of bytes and then process the
bytes. (For example, the streambuf functions take and return
variables of type <code class="code">int_type</code>.)
</p><p>Another area of problems is opening text files in binary mode.
Generally, binary mode is intended for binary files, and opening
text files in binary mode means that you now have to deal with all of
those end-of-line and end-of-file problems that we mentioned before.
</p><p>
An instructive thread from comp.lang.c++.moderated delved off into
this topic starting more or less at
<a class="ulink" href="http://groups.google.com/group/comp.std.c++/browse_thread/thread/f87b4abd7954a87/946a3eb9921e382d?q=comp.std.c%2B%2B+binary+iostream#946a3eb9921e382d" target="_top">this</a>
post and continuing to the end of the thread. (The subject heading is "binary iostreams" on both comp.std.c++
and comp.lang.c++.moderated.) Take special note of the replies by James Kanze and Dietmar Kühl.
</p><p>Briefly, the problems of byte ordering and type sizes mean that
the unformatted functions like <code class="code">ostream::put()</code> and
<code class="code">istream::get()</code> cannot safely be used to communicate
between arbitrary programs, or across a network, or from one
invocation of a program to another invocation of the same program
on a different platform, etc.
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Pathetic Performance? Ditch C.
</p><p>It sounds like a flame on C, but it isn't. Really. Calm down.
I'm just saying it to get your attention.
</p><p>Because the C++ library includes the C library, both C-style and
C++-style I/O have to work at the same time. For example:
</p><pre class="programlisting">
#include &lt;iostream&gt;
#include &lt;cstdio&gt;
std::cout &lt;&lt; "Hel";
std::printf ("lo, worl");
std::cout &lt;&lt; "d!\n";
</pre><p>This must do what you think it does.
</p><p>Alert members of the audience will immediately notice that buffering
is going to make a hash of the output unless special steps are taken.
</p><p>The special steps taken by libstdc++, at least for version 3.0,
involve doing very little buffering for the standard streams, leaving
most of the buffering to the underlying C library. (This kind of
thing is tricky to get right.)
The upside is that correctness is ensured. The downside is that
writing through <code class="code">cout</code> can quite easily lead to awful
performance when the C++ I/O library is layered on top of the C I/O
library (as it is for 3.0 by default). Some patches have been applied
which improve the situation for 3.1.
</p><p>However, the C and C++ standard streams only need to be kept in sync
when both libraries' facilities are in use. If your program only uses
C++ I/O, then there's no need to sync with the C streams. The right
thing to do in this case is to call
</p><pre class="programlisting">
#include <span class="emphasis"><em>any of the I/O headers such as ios, iostream, etc</em></span>
std::ios::sync_with_stdio(false);
</pre><p>You must do this before performing any I/O via the C++ stream objects.
Once you call this, the C++ streams will operate independently of the
(unused) C streams. For GCC 3.x, this means that <code class="code">cout</code> and
company will become fully buffered on their own.
</p><p>Note, by the way, that the synchronization requirement only applies to
the standard streams (<code class="code">cin</code>, <code class="code">cout</code>,
<code class="code">cerr</code>,
<code class="code">clog</code>, and their wide-character counterparts). File stream
objects that you declare yourself have no such requirement and are fully
buffered.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="io_and_c.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="io_and_c.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="extensions.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 28. Interacting with C </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part XII. 
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</p><div class="sect2" title="Using the Debug Mode"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.using.mode"></a>Using the Debug Mode</h3></div></div></div><p>To use the libstdc++ debug mode, compile your application with the
compiler flag <code class="code">-D_GLIBCXX_DEBUG</code>. Note that this flag
changes the sizes and behavior of standard class templates such
as <code class="code">std::vector</code>, and therefore you can only link code
compiled with debug mode and code compiled without debug mode if no
instantiation of a container is passed between the two translation
units.</p><p>By default, error messages are formatted to fit on lines of about
78 characters. The environment variable
<code class="code">GLIBCXX_DEBUG_MESSAGE_LENGTH</code> can be used to request a
different length.</p></div><div class="sect2" title="Using a Specific Debug Container"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.using.specific"></a>Using a Specific Debug Container</h3></div></div></div><p>When it is not feasible to recompile your entire application, or
only specific containers need checking, debugging containers are
available as GNU extensions. These debugging containers are
functionally equivalent to the standard drop-in containers used in
debug mode, but they are available in a separate namespace as GNU
extensions and may be used in programs compiled with either release
mode or with debug mode. The
following table provides the names and headers of the debugging
containers:
</p><div class="table"><a id="id705570"></a><p class="title"><b>Table 30.1. Debugging Containers</b></p><div class="table-contents"><table summary="Debugging Containers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Container</th><th align="left">Header</th><th align="left">Debug container</th><th align="left">Debug header</th></tr></thead><tbody><tr><td align="left"><code class="classname">std::bitset</code></td><td align="left"><code class="filename">bitset</code></td><td align="left"><code class="classname">__gnu_debug::bitset</code></td><td align="left"><code class="filename">bitset</code></td></tr><tr><td align="left"><code class="classname">std::deque</code></td><td align="left"><code class="filename">deque</code></td><td align="left"><code class="classname">__gnu_debug::deque</code></td><td align="left"><code class="filename">deque</code></td></tr><tr><td align="left"><code class="classname">std::list</code></td><td align="left"><code class="filename">list</code></td><td align="left"><code class="classname">__gnu_debug::list</code></td><td align="left"><code class="filename">list</code></td></tr><tr><td align="left"><code class="classname">std::map</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="classname">__gnu_debug::map</code></td><td align="left"><code class="filename">map</code></td></tr><tr><td align="left"><code class="classname">std::multimap</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="classname">__gnu_debug::multimap</code></td><td align="left"><code class="filename">map</code></td></tr><tr><td align="left"><code class="classname">std::multiset</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="classname">__gnu_debug::multiset</code></td><td align="left"><code class="filename">set</code></td></tr><tr><td align="left"><code class="classname">std::set</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="classname">__gnu_debug::set</code></td><td align="left"><code class="filename">set</code></td></tr><tr><td align="left"><code class="classname">std::string</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="classname">__gnu_debug::string</code></td><td align="left"><code class="filename">string</code></td></tr><tr><td align="left"><code class="classname">std::wstring</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="classname">__gnu_debug::wstring</code></td><td align="left"><code class="filename">string</code></td></tr><tr><td align="left"><code class="classname">std::basic_string</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="classname">__gnu_debug::basic_string</code></td><td align="left"><code class="filename">string</code></td></tr><tr><td align="left"><code class="classname">std::vector</code></td><td align="left"><code class="filename">vector</code></td><td align="left"><code class="classname">__gnu_debug::vector</code></td><td align="left"><code class="filename">vector</code></td></tr></tbody></table></div></div><br class="table-break" /><p>In addition, when compiling in C++0x mode, these additional
containers have additional debug capability.
</p><div class="table"><a id="id607020"></a><p class="title"><b>Table 30.2. Debugging Containers C++0x</b></p><div class="table-contents"><table summary="Debugging Containers C++0x" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Container</th><th align="left">Header</th><th align="left">Debug container</th><th align="left">Debug header</th></tr></thead><tbody><tr><td align="left"><code class="classname">std::unordered_map</code></td><td align="left"><code class="filename">unordered_map</code></td><td align="left"><code class="classname">__gnu_debug::unordered_map</code></td><td align="left"><code class="filename">unordered_map</code></td></tr><tr><td align="left"><code class="classname">std::unordered_multimap</code></td><td align="left"><code class="filename">unordered_map</code></td><td align="left"><code class="classname">__gnu_debug::unordered_multimap</code></td><td align="left"><code class="filename">unordered_map</code></td></tr><tr><td align="left"><code class="classname">std::unordered_set</code></td><td align="left"><code class="filename">unordered_set</code></td><td align="left"><code class="classname">__gnu_debug::unordered_set</code></td><td align="left"><code class="filename">unordered_set</code></td></tr><tr><td align="left"><code class="classname">std::unordered_multiset</code></td><td align="left"><code class="filename">unordered_set</code></td><td align="left"><code class="classname">__gnu_debug::unordered_multiset</code></td><td align="left"><code class="filename">unordered_set</code></td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch30s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="debug_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch30s04.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Semantics </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Design</td></tr></table></div></body></html>
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</p><div class="sect1" title="complex Processing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="numerics.complex.processing"></a>complex Processing</h2></div></div></div><p>
</p><p>Using <code class="code">complex&lt;&gt;</code> becomes even more comple- er, sorry,
<span class="emphasis"><em>complicated</em></span>, with the not-quite-gratuitously-incompatible
addition of complex types to the C language. David Tribble has
compiled a list of C++98 and C99 conflict points; his description of
C's new type versus those of C++ and how to get them playing together
nicely is
<a class="ulink" href="http://david.tribble.com/text/cdiffs.htm#C99-complex" target="_top">here</a>.
</p><p><code class="code">complex&lt;&gt;</code> is intended to be instantiated with a
floating-point type. As long as you meet that and some other basic
requirements, then the resulting instantiation has all of the usual
math operators defined, as well as definitions of <code class="code">op&lt;&lt;</code>
and <code class="code">op&gt;&gt;</code> that work with iostreams: <code class="code">op&lt;&lt;</code>
prints <code class="code">(u,v)</code> and <code class="code">op&gt;&gt;</code> can read <code class="code">u</code>,
<code class="code">(u)</code>, and <code class="code">(u,v)</code>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="numerics.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="numerics.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="generalized_numeric_operations.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part X. 
Numerics
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Concurrency
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Standard Contents
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Concurrency
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</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="concurrency.html#std.concurrency.api">API Reference</a></span></dt></dl></div><p>
Facilities for concurrent operation, and control thereof.
</p><div class="sect1" title="API Reference"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.concurrency.api"></a>API Reference</h2></div></div></div><p>
All items are declared in one of four standard header files.
</p><p>
In header <code class="filename">mutex</code>, class
template <code class="classname">mutex</code> and variants,
class <code class="classname">once_flag</code>, and class
template <code class="classname">unique_lock</code>.
</p><p>
In header <code class="filename">condition_variable</code>,
classes <code class="classname">condition_variable</code>
and <code class="classname">condition_variable_any</code>.
</p><p>
In header <code class="filename">thread</code>,
class <code class="classname">thread</code> and
namespace <code class="code">this_thread</code>.
</p><p>
In header <code class="filename">future</code>, class
template <code class="classname">future</code> and class
template <code class="classname">shared_future</code>, class
template <code class="classname">promise</code>,
and <code class="classname">packaged_task</code>.
</p><p>
Full API details.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="atomics.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="extensions.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 14. 
Atomics
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Extensions
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Part VII.  Containers</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="spine.html" title="The GNU C++ Library" /><link rel="prev" href="messages.html" title="messages" /><link rel="next" href="sequences.html" title="Chapter 16. Sequences" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Part VII
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 9.  Containers</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt02.html" title="Part II.  Standard Contents" /><link rel="prev" href="facets.html" title="Facets" /><link rel="next" href="associative.html" title="Associative" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 9
Containers
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</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="facets.html">Prev</a> </td><th width="60%" align="center">Part II. 
Standard Contents
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Containers
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</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="containers.html#std.containers.sequences">Sequences</a></span></dt><dd><dl><dt><span class="sect2"><a href="containers.html#containers.sequences.list">list</a></span></dt><dt><span class="sect2"><a href="containers.html#containers.sequences.vector">vector</a></span></dt></dl></dd><dt><span class="sect1"><a href="associative.html">Associative</a></span></dt><dd><dl><dt><span class="sect2"><a href="associative.html#containers.associative.insert_hints">Insertion Hints</a></span></dt><dt><span class="sect2"><a href="associative.html#containers.associative.bitset">bitset</a></span></dt></dl></dd><dt><span class="sect1"><a href="containers_and_c.html">Interacting with C</a></span></dt><dd><dl><dt><span class="sect2"><a href="containers_and_c.html#containers.c.vs_array">Containers vs. Arrays</a></span></dt></dl></dd></dl></div><div class="sect1" title="Sequences"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.containers.sequences"></a>Sequences</h2></div></div></div><div class="sect2" title="list"><div class="titlepage"><div><div><h3 class="title"><a id="containers.sequences.list"></a>list</h3></div></div></div><div class="sect3" title="list::size() is O(n)"><div class="titlepage"><div><div><h4 class="title"><a id="sequences.list.size"></a>list::size() is O(n)</h4></div></div></div><p>
Yes it is, and that's okay. This is a decision that we preserved
when we imported SGI's STL implementation. The following is
quoted from <a class="ulink" href="http://www.sgi.com/tech/stl/FAQ.html" target="_top">their FAQ</a>:
</p><div class="blockquote"><blockquote class="blockquote"><p>
The size() member function, for list and slist, takes time
proportional to the number of elements in the list. This was a
deliberate tradeoff. The only way to get a constant-time
size() for linked lists would be to maintain an extra member
variable containing the list's size. This would require taking
extra time to update that variable (it would make splice() a
linear time operation, for example), and it would also make the
list larger. Many list algorithms don't require that extra
word (algorithms that do require it might do better with
vectors than with lists), and, when it is necessary to maintain
an explicit size count, it's something that users can do
themselves.
</p><p>
This choice is permitted by the C++ standard. The standard says
that size() <span class="quote"><span class="quote">should</span></span> be constant time, and
<span class="quote"><span class="quote">should</span></span> does not mean the same thing as
<span class="quote"><span class="quote">shall</span></span>. This is the officially recommended ISO
wording for saying that an implementation is supposed to do
something unless there is a good reason not to.
</p><p>
One implication of linear time size(): you should never write
</p><pre class="programlisting">
if (L.size() == 0)
...
</pre><p>
Instead, you should write
</p><pre class="programlisting">
if (L.empty())
...
</pre></blockquote></div></div></div><div class="sect2" title="vector"><div class="titlepage"><div><div><h3 class="title"><a id="containers.sequences.vector"></a>vector</h3></div></div></div><p>
</p><div class="sect3" title="Space Overhead Management"><div class="titlepage"><div><div><h4 class="title"><a id="sequences.vector.management"></a>Space Overhead Management</h4></div></div></div><p>
In <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-04/msg00105.html" target="_top">this
message to the list</a>, Daniel Kostecky announced work on an
alternate form of <code class="code">std::vector</code> that would support
hints on the number of elements to be over-allocated. The design
was also described, along with possible implementation choices.
</p><p>
The first two alpha releases were announced <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-07/msg00048.html" target="_top">here</a>
and <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2002-07/msg00111.html" target="_top">here</a>.
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</th><td width="20%" align="right"> <a accesskey="n" href="iterators.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Interacting with C"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.containers.c"></a>Interacting with C</h2></div></div></div><div class="sect2" title="Containers vs. Arrays"><div class="titlepage"><div><div><h3 class="title"><a id="containers.c.vs_array"></a>Containers vs. Arrays</h3></div></div></div><p>
You're writing some code and can't decide whether to use builtin
arrays or some kind of container. There are compelling reasons
to use one of the container classes, but you're afraid that
......@@ -18,7 +18,7 @@
container classes, these are iterators (usually
<code class="code">begin()</code> and <code class="code">end()</code>, but not always).
For builtin arrays, these are the address of the first element
and the <a class="link" href="bk01pt08ch19s02.html" title="One Past the End">past-the-end</a> element.
and the <a class="link" href="iterators.html#iterators.predefined.end" title="One Past the End">past-the-end</a> element.
</p><p>
Some very simple wrapper functions can hide all of that from the
rest of the code. For example, a pair of functions called
......@@ -48,27 +48,27 @@ template&lt;typename T&gt;
{ return v.begin(); }
template&lt;typename T, unsigned int sz&gt;
inline T*
inline T*
beginof(T (&amp;array)[sz]) { return array; }
// endof
template&lt;typename T&gt;
inline typename vector&lt;T&gt;::iterator
inline typename vector&lt;T&gt;::iterator
endof(vector&lt;T&gt; &amp;v)
{ return v.end(); }
template&lt;typename T, unsigned int sz&gt;
inline T*
inline T*
endof(T (&amp;array)[sz]) { return array + sz; }
// lengthof
template&lt;typename T&gt;
inline typename vector&lt;T&gt;::size_type
inline typename vector&lt;T&gt;::size_type
lengthof(vector&lt;T&gt; &amp;v)
{ return v.size(); }
template&lt;typename T, unsigned int sz&gt;
inline unsigned int
inline unsigned int
lengthof(T (&amp;)[sz]) { return sz; }
</pre><p>
Astute readers will notice two things at once: first, that the
......@@ -81,10 +81,10 @@ template&lt;typename T, unsigned int sz&gt;
</p><p>
Second, the line
</p><pre class="programlisting">
inline unsigned int lengthof (T (&amp;)[sz]) { return sz; }
inline unsigned int lengthof (T (&amp;)[sz]) { return sz; }
</pre><p>
looks just weird! Hint: unused parameters can be left nameless.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bitset.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="containers.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="iterators.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">bitset </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part VIII
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</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch17s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 17. Debug Mode"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.debug_mode"></a>Chapter 17. Debug Mode</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="debug_mode.html#manual.ext.debug_mode.intro">Intro</a></span></dt><dt><span class="sect1"><a href="bk01pt03ch17s02.html">Semantics</a></span></dt><dt><span class="sect1"><a href="bk01pt03ch17s03.html">Using</a></span></dt><dd><dl><dt><span class="sect2"><a href="bk01pt03ch17s03.html#debug_mode.using.mode">Using the Debug Mode</a></span></dt><dt><span class="sect2"><a href="bk01pt03ch17s03.html#debug_mode.using.specific">Using a Specific Debug Container</a></span></dt></dl></dd><dt><span class="sect1"><a href="bk01pt03ch17s04.html">Design</a></span></dt><dd><dl><dt><span class="sect2"><a href="bk01pt03ch17s04.html#debug_mode.design.goals">Goals</a></span></dt><dt><span class="sect2"><a href="bk01pt03ch17s04.html#debug_mode.design.methods">Methods</a></span></dt><dt><span class="sect2"><a href="bk01pt03ch17s04.html#debug_mode.design.other">Other Implementations</a></span></dt></dl></dd></dl></div><div class="sect1" title="Intro"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.debug_mode.intro"></a>Intro</h2></div></div></div><p>
By default, libstdc++ is built with efficiency in mind, and
therefore performs little or no error checking that is not
required by the C++ standard. This means that programs that
......@@ -15,7 +15,7 @@
library facilities, and will report errors in the use of libstdc++
as soon as they can be detected by emitting a description of the
problem to standard error and aborting the program. This debug
mode is available with GCC 3.4.0 and later versions.
mode is available with GCC 3.4.0 and later versions.
</p><p>
The libstdc++ debug mode performs checking for many areas of the
C++ standard, but the focus is on checking interactions among
......@@ -34,4 +34,4 @@
the same predicate that was passed
to <code class="code">set_intersection</code>; the libstdc++ debug mode will
detect an error if the sequence is not sorted or was sorted by a
different predicate.</p></li></ul></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_compile_checks.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch30s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 29. Compile Time Checks </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Semantics</td></tr></table></div></body></html>
different predicate.</p></li></ul></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_compile_checks.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch17s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 16. Compile Time Checks </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Semantics</td></tr></table></div></body></html>
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Diagnostics
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<a id="id477731" class="indexterm"></a>
</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="diagnostics.html#std.diagnostics.exceptions">Exceptions</a></span></dt><dd><dl><dt><span class="sect2"><a href="diagnostics.html#std.diagnostics.exceptions.api">API Reference</a></span></dt><dt><span class="sect2"><a href="diagnostics.html#std.diagnostics.exceptions.data">Adding Data to <code class="classname">exception</code></a></span></dt></dl></dd><dt><span class="sect1"><a href="bk01pt02ch05s02.html">Concept Checking</a></span></dt></dl></div><div class="sect1" title="Exceptions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.diagnostics.exceptions"></a>Exceptions</h2></div></div></div><div class="sect2" title="API Reference"><div class="titlepage"><div><div><h3 class="title"><a id="std.diagnostics.exceptions.api"></a>API Reference</h3></div></div></div><p>
All exception objects are defined in one of the standard header
files: <code class="filename">exception</code>,
<code class="filename">stdexcept</code>, <code class="filename">new</code>, and
<code class="filename">typeinfo</code>.
</p><p>
The base exception object is <code class="classname">exception</code>,
located in <code class="filename">exception</code>. This object has no
<code class="classname">string</code> member.
</p><p>
Derived from this are several classes that may have a
<code class="classname">string</code> member: a full hierarchy can be
found in the source documentation.
</p><p>
Full API details.
</p></div><div class="sect2" title="Adding Data to exception"><div class="titlepage"><div><div><h3 class="title"><a id="std.diagnostics.exceptions.data"></a>Adding Data to <code class="classname">exception</code></h3></div></div></div><p>
The standard exception classes carry with them a single string as
data (usually describing what went wrong or where the 'throw' took
place). It's good to remember that you can add your own data to
these exceptions when extending the hierarchy:
</p><pre class="programlisting">
struct My_Exception : public std::runtime_error
{
public:
My_Exception (const string&amp; whatarg)
: std::runtime_error(whatarg), e(errno), id(GetDataBaseID()) { }
int errno_at_time_of_throw() const { return e; }
DBID id_of_thing_that_threw() const { return id; }
protected:
int e;
DBID id; // some user-defined type
};
</pre></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="termination.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt02ch05s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Termination </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Concept Checking</td></tr></table></div></body></html>
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Support
</th><td width="20%" align="right"> <a accesskey="n" href="termination.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 5. Dynamic Memory"><div class="titlepage"><div><div><h2 class="title"><a id="manual.support.memory"></a>Chapter 5. Dynamic Memory</h2></div></div></div><p>
</th><td width="20%" align="right"> <a accesskey="n" href="termination.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Dynamic Memory"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.support.memory"></a>Dynamic Memory</h2></div></div></div><p>
There are six flavors each of <code class="function">new</code> and
<code class="function">delete</code>, so make certain that you're using the right
ones. Here are quickie descriptions of <code class="function">new</code>:
......@@ -51,8 +51,8 @@
{
delete[] safety;
popup_window ("Dude, you are running low on heap memory. You
should, like, close some windows, or something.
The next time you run out, we're gonna burn!");
should, like, close some windows, or something.
The next time you run out, we're gonna burn!");
set_new_handler (old_handler);
return;
}
......@@ -65,5 +65,8 @@
}
</pre><p>
<code class="classname">bad_alloc</code> is derived from the base <code class="classname">exception</code>
class defined in Chapter 19.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt02ch04s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="support.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="termination.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">NULL </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 6. Termination</td></tr></table></div></body></html>
class defined in Sect1 19.
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All exception objects are defined in one of the standard header
files: <code class="filename">exception</code>,
<code class="filename">stdexcept</code>, <code class="filename">new</code>, and
<code class="filename">typeinfo</code>.
</p><p>
The base exception object is <code class="classname">exception</code>,
located in <code class="filename">exception</code>. This object has no
<code class="classname">string</code> member.
</p><p>
Derived from this are several classes that may have a
<code class="classname">string</code> member: a full hierarchy can be
found in the <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00460.html" target="_top">source documentation</a>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="diagnostics.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="diagnostics.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch07s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part III. 
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 36. Algorithms</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="extensions.html" title="Part XII.  Extensions" /><link rel="prev" href="ext_utilities.html" title="Chapter 35. Utilities" /><link rel="next" href="ext_numerics.html" title="Chapter 37. Numerics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 36. Algorithms</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_utilities.html">Prev</a> </td><th width="60%" align="center">Part XII. 
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 23. Algorithms</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="extensions.html" title="Part III.  Extensions" /><link rel="prev" href="ext_utilities.html" title="Chapter 22. Utilities" /><link rel="next" href="ext_numerics.html" title="Chapter 24. Numerics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 23. Algorithms</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_utilities.html">Prev</a> </td><th width="60%" align="center">Part III. 
Extensions
</th><td width="20%" align="right"> <a accesskey="n" href="ext_numerics.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 36. Algorithms"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.algorithms"></a>Chapter 36. Algorithms</h2></div></div></div><p>25.1.6 (count, count_if) is extended with two more versions of count
</th><td width="20%" align="right"> <a accesskey="n" href="ext_numerics.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 23. Algorithms"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.algorithms"></a>Chapter 23. Algorithms</h2></div></div></div><p>25.1.6 (count, count_if) is extended with two more versions of count
and count_if. The standard versions return their results. The
additional signatures return void, but take a final parameter by
reference to which they assign their results, e.g.,
......@@ -16,8 +16,8 @@
</p><p>25.3 (sorting 'n' heaps 'n' stuff) is extended with some helper
predicates. Look in the doxygen-generated pages for notes on these.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">is_heap</code> tests whether or not a range is a heap.</p></li><li class="listitem"><p><code class="code">is_sorted</code> tests whether or not a range is sorted in
nondescending order.</p></li></ul></div><p>25.3.8 (lexicographical_compare) is extended with
nondescending order.</p></li></ul></div><p>25.3.8 (lexicographical_compare) is extended with
</p><pre class="programlisting">
lexicographical_compare_3way(_InputIter1 first1, _InputIter1 last1,
_InputIter2 first2, _InputIter2 last2)</pre><p>which does... what?
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_InputIter2 first2, _InputIter2 last2)</pre><p>which does... what?
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_utilities.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_numerics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 22. Utilities </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 24. Numerics</td></tr></table></div></body></html>
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</th><td width="20%" align="right"> <a accesskey="n" href="debug_mode.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 16. Compile Time Checks"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.compile_checks"></a>Chapter 16. Compile Time Checks</h2></div></div></div><p>
Also known as concept checking.
</p><p>In 1999, SGI added <span class="emphasis"><em>concept checkers</em></span> to their implementation
of the STL: code which checked the template parameters of
......@@ -37,4 +37,4 @@
support for template parameter constraints based on concepts in the core
language. This will obviate the need for the library-simulated concept
checking described above.
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constructs for playing with threads. In contrast to the atomics layer,
the concurrence layer consists largely of types. All types are defined within <code class="code">namespace __gnu_cxx</code>.
</p><p>
......@@ -31,7 +31,7 @@ locks it during construction of <code class="code">__scoped_locke</code> and
unlocks it during destruction. This is an efficient way of locking
critical sections, while retaining exception-safety.
</p></div><div class="sect2" title="Interface to Atomic Functions"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.design.atomics"></a>Interface to Atomic Functions</h3></div></div></div><p>
Two functions and one type form the base of atomic support.
Two functions and one type form the base of atomic support.
</p><p>The type <code class="code">_Atomic_word</code> is a signed integral type
supporting atomic operations.
</p><p>
......@@ -56,7 +56,7 @@ __atomic_add_dispatch
</p><p>Adds the second argument's value to the first argument. Has no return value.
</p></li></ul></div><p>
These functions forward to one of several specialized helper
functions, depending on the circumstances. For instance,
functions, depending on the circumstances. For instance,
</p><p>
<code class="code">
__exchange_and_add_dispatch
......@@ -67,7 +67,7 @@ Calls through to either of:
</p><p>Multi-thread version. Inlined if compiler-generated builtin atomics
can be used, otherwise resolved at link time to a non-builtin code
sequence.
</p></li><li class="listitem"><p><code class="code">__exchange_and_add_single</code>
</p></li><li class="listitem"><p><code class="code">__exchange_and_add_single</code>
</p><p>Single threaded version. Inlined.</p></li></ul></div><p>However, only <code class="code">__exchange_and_add_dispatch</code>
and <code class="code">__atomic_add_dispatch</code> should be used. These functions
can be used in a portable manner, regardless of the specific
......@@ -79,13 +79,13 @@ operations.)
In addition, there are two macros
</p><p>
<code class="code">
_GLIBCXX_READ_MEM_BARRIER
_GLIBCXX_READ_MEM_BARRIER
</code>
</p><p>
<code class="code">
_GLIBCXX_WRITE_MEM_BARRIER
_GLIBCXX_WRITE_MEM_BARRIER
</code>
</p><p>
Which expand to the appropriate write and read barrier required by the
host hardware and operating system.
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</th><td width="20%" align="right"> <a accesskey="n" href="ext_concurrency.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 27. Demangling"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.demangle"></a>Chapter 27. Demangling</h2></div></div></div><p>
Transforming C++ ABI identifiers (like RTTI symbols) into the
original C++ source identifiers is called
<span class="quote"><span class="quote">demangling.</span></span>
......@@ -63,7 +63,7 @@ int main()
</p><pre class="screen">
<code class="computeroutput">
St13bad_exception =&gt; std::bad_exception : 0
3barI5emptyLi17EE =&gt; bar&lt;empty, 17&gt; : 0
3barI5emptyLi17EE =&gt; bar&lt;empty, 17&gt; : 0
</code>
</pre><p>
The demangler interface is described in the source documentation
......@@ -71,4 +71,4 @@ int main()
be writing C++ in order to demangle C++. (That also means we have to
use crummy memory management facilities, so don't forget to free()
the returned char array.)
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</th><td width="20%" align="right"> <a accesskey="n" href="ext_demangling.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 26. Input and Output"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.io"></a>Chapter 26. Input and Output</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="ext_io.html#manual.ext.io.filebuf_derived">Derived filebufs</a></span></dt></dl></div><p>
Extensions allowing <code class="code">filebuf</code>s to be constructed from
"C" types like FILE*s and file descriptors.
</p><div class="sect1" title="Derived filebufs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.io.filebuf_derived"></a>Derived filebufs</h2></div></div></div><p>The v2 library included non-standard extensions to construct
......@@ -13,38 +13,38 @@
IOStreams is via the <code class="code">stdio_filebuf</code> class (see below),
but earlier releases provided slightly different mechanisms.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>3.0.x <code class="code">filebuf</code>s have another ctor with this signature:
<code class="code">basic_filebuf(__c_file_type*, ios_base::openmode, int_type);
<code class="code">basic_filebuf(__c_file_type*, ios_base::openmode, int_type);
</code>
This comes in very handy in a number of places, such as
attaching Unix sockets, pipes, and anything else which uses file
descriptors, into the IOStream buffering classes. The three
arguments are as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><code class="code">__c_file_type* F </code>
// the __c_file_type typedef usually boils down to stdio's FILE
</p></li><li class="listitem"><p><code class="code">ios_base::openmode M </code>
// same as all the other uses of openmode
</p></li><li class="listitem"><p><code class="code">int_type B </code>
// buffer size, defaults to BUFSIZ if not specified
</p></li></ul></div><p>
For those wanting to use file descriptors instead of FILE*'s, I
invite you to contemplate the mysteries of C's <code class="code">fdopen()</code>.
This comes in very handy in a number of places, such as
attaching Unix sockets, pipes, and anything else which uses file
descriptors, into the IOStream buffering classes. The three
arguments are as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><code class="code">__c_file_type* F </code>
// the __c_file_type typedef usually boils down to stdio's FILE
</p></li><li class="listitem"><p><code class="code">ios_base::openmode M </code>
// same as all the other uses of openmode
</p></li><li class="listitem"><p><code class="code">int_type B </code>
// buffer size, defaults to BUFSIZ if not specified
</p></li></ul></div><p>
For those wanting to use file descriptors instead of FILE*'s, I
invite you to contemplate the mysteries of C's <code class="code">fdopen()</code>.
</p></li><li class="listitem"><p>In library snapshot 3.0.95 and later, <code class="code">filebuf</code>s bring
back an old extension: the <code class="code">fd()</code> member function. The
integer returned from this function can be used for whatever file
descriptors can be used for on your platform. Naturally, the
library cannot track what you do on your own with a file descriptor,
so if you perform any I/O directly, don't expect the library to be
aware of it.
back an old extension: the <code class="code">fd()</code> member function. The
integer returned from this function can be used for whatever file
descriptors can be used for on your platform. Naturally, the
library cannot track what you do on your own with a file descriptor,
so if you perform any I/O directly, don't expect the library to be
aware of it.
</p></li><li class="listitem"><p>Beginning with 3.1, the extra <code class="code">filebuf</code> constructor and
the <code class="code">fd()</code> function were removed from the standard
filebuf. Instead, <code class="code">&lt;ext/stdio_filebuf.h&gt;</code> contains
a derived class called
<a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00074.html" target="_top"><code class="code">__gnu_cxx::stdio_filebuf</code></a>.
This class can be constructed from a C <code class="code">FILE*</code> or a file
descriptor, and provides the <code class="code">fd()</code> function.
the <code class="code">fd()</code> function were removed from the standard
filebuf. Instead, <code class="code">&lt;ext/stdio_filebuf.h&gt;</code> contains
a derived class called
<a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00074.html" target="_top"><code class="code">__gnu_cxx::stdio_filebuf</code></a>.
This class can be constructed from a C <code class="code">FILE*</code> or a file
descriptor, and provides the <code class="code">fd()</code> function.
</p></li></ul></div><p>If you want to access a <code class="code">filebuf</code>'s file descriptor to
implement file locking (e.g. using the <code class="code">fcntl()</code> system
call) then you might be interested in Henry Suter's RWLock class.
</p><p>
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_iterators.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_demangling.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 38. Iterators </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 40. Demangling</td></tr></table></div></body></html>
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Extensions
</th><td width="20%" align="right"> <a accesskey="n" href="ext_io.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 38. Iterators"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.iterators"></a>Chapter 38. Iterators</h2></div></div></div><p>24.3.2 describes <code class="code">struct iterator</code>, which didn't exist in the
</th><td width="20%" align="right"> <a accesskey="n" href="ext_io.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 25. Iterators"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.iterators"></a>Chapter 25. Iterators</h2></div></div></div><p>24.3.2 describes <code class="code">struct iterator</code>, which didn't exist in the
original HP STL implementation (the language wasn't rich enough at the
time). For backwards compatibility, base classes are provided which
declare the same nested typedefs:
......@@ -11,4 +11,4 @@
two iterators and returns a result. It is extended by another signature
which takes two iterators and a reference to a result. The result is
modified, and the function returns nothing.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_numerics.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_io.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 37. Numerics </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 39. Input and Output</td></tr></table></div></body></html>
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_numerics.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_io.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 24. Numerics </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 26. Input and Output</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 37. Numerics</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="extensions.html" title="Part XII.  Extensions" /><link rel="prev" href="ext_algorithms.html" title="Chapter 36. Algorithms" /><link rel="next" href="ext_iterators.html" title="Chapter 38. Iterators" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 37. Numerics</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_algorithms.html">Prev</a> </td><th width="60%" align="center">Part XII. 
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Extensions
</th><td width="20%" align="right"> <a accesskey="n" href="ext_iterators.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 37. Numerics"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.numerics"></a>Chapter 37. Numerics</h2></div></div></div><p>26.4, the generalized numeric operations such as accumulate, are extended
</th><td width="20%" align="right"> <a accesskey="n" href="ext_iterators.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 24. Numerics"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.numerics"></a>Chapter 24. Numerics</h2></div></div></div><p>26.4, the generalized numeric operations such as accumulate, are extended
with the following functions:
</p><pre class="programlisting">
power (x, n);
......@@ -17,4 +17,4 @@
That is, it assigns value to *first, value + 1 to *(first + 1) and so
on." Quoted from SGI documentation.
</p><pre class="programlisting">
void iota(_ForwardIter first, _ForwardIter last, _Tp value);</pre></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_algorithms.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_iterators.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 36. Algorithms </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 38. Iterators</td></tr></table></div></body></html>
void iota(_ForwardIter first, _ForwardIter last, _Tp value);</pre></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_algorithms.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_iterators.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 23. Algorithms </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 25. Iterators</td></tr></table></div></body></html>
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Extensions
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</th><td width="20%" align="right"> <a accesskey="n" href="ext_algorithms.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 22. Utilities"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.util"></a>Chapter 22. Utilities</h2></div></div></div><p>
The &lt;functional&gt; header contains many additional functors
and helper functions, extending section 20.3. They are
implemented in the file stl_function.h:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">identity_element</code> for addition and multiplication. *
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">identity_element</code> for addition and multiplication. *
</p></li><li class="listitem"><p>The functor <code class="code">identity</code>, whose <code class="code">operator()</code>
returns the argument unchanged. *
returns the argument unchanged. *
</p></li><li class="listitem"><p>Composition functors <code class="code">unary_function</code> and
<code class="code">binary_function</code>, and their helpers <code class="code">compose1</code>
and <code class="code">compose2</code>. *
</p></li><li class="listitem"><p><code class="code">select1st</code> and <code class="code">select2nd</code>, to strip pairs. *
and <code class="code">compose2</code>. *
</p></li><li class="listitem"><p><code class="code">select1st</code> and <code class="code">select2nd</code>, to strip pairs. *
</p></li><li class="listitem"><p><code class="code">project1st</code> and <code class="code">project2nd</code>. * </p></li><li class="listitem"><p>A set of functors/functions which always return the same result. They
are <code class="code">constant_void_fun</code>, <code class="code">constant_binary_fun</code>,
<code class="code">constant_unary_fun</code>, <code class="code">constant0</code>,
......@@ -38,4 +38,4 @@ get_temporary_buffer(5, (int*)0);
</p><p>
The specialized algorithms of section 20.4.4 are extended with
<code class="code">uninitialized_copy_n</code>. *
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch34s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_algorithms.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Deprecated HP/SGI </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 36. Algorithms</td></tr></table></div></body></html>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 9. Functors</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="utilities.html" title="Part IV.  Utilities" /><link rel="prev" href="utilities.html" title="Part IV.  Utilities" /><link rel="next" href="pairs.html" title="Chapter 10. Pairs" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 9. Functors</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="utilities.html">Prev</a> </td><th width="60%" align="center">Part IV. 
Utilities
</th><td width="20%" align="right"> <a accesskey="n" href="pairs.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 9. Functors"><div class="titlepage"><div><div><h2 class="title"><a id="manual.util.functors"></a>Chapter 9. Functors</h2></div></div></div><p>If you don't know what functors are, you're not alone. Many people
get slightly the wrong idea. In the interest of not reinventing
the wheel, we will refer you to the introduction to the functor
concept written by SGI as part of their STL, in
<a class="ulink" href="http://www.sgi.com/tech/stl/functors.html" target="_top">their
http://www.sgi.com/tech/stl/functors.html</a>.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="utilities.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="utilities.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pairs.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part IV. 
Utilities
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 4. Types</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="support.html" title="Part II.  Support" /><link rel="prev" href="bk01pt02pr01.html" title="" /><link rel="next" href="bk01pt02ch04s02.html" title="Numeric Properties" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 4. Types</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt02pr01.html">Prev</a> </td><th width="60%" align="center">Part II. 
Support
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C++ has the following builtin types:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
char
</p></li><li class="listitem"><p>
signed char
</p></li><li class="listitem"><p>
unsigned char
</p></li><li class="listitem"><p>
signed short
</p></li><li class="listitem"><p>
signed int
</p></li><li class="listitem"><p>
signed long
</p></li><li class="listitem"><p>
unsigned short
</p></li><li class="listitem"><p>
unsigned int
</p></li><li class="listitem"><p>
unsigned long
</p></li><li class="listitem"><p>
bool
</p></li><li class="listitem"><p>
wchar_t
</p></li><li class="listitem"><p>
float
</p></li><li class="listitem"><p>
double
</p></li><li class="listitem"><p>
long double
</p></li></ul></div><p>
These fundamental types are always available, without having to
include a header file. These types are exactly the same in
either C++ or in C.
</p><p>
Specializing parts of the library on these types is prohibited:
instead, use a POD.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt02pr01.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="support.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt02ch04s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"> </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Numeric Properties</td></tr></table></div></body></html>
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</th><td width="20%" align="right"> <a accesskey="n" href="numerics_and_c.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Generalized Operations"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.numerics.generalized_ops"></a>Generalized Operations</h2></div></div></div><p>
</p><p>There are four generalized functions in the &lt;numeric&gt; header
that follow the same conventions as those in &lt;algorithm&gt;. Each
of them is overloaded: one signature for common default operations,
and a second for fully general operations. Their names are
self-explanatory to anyone who works with numerics on a regular basis:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">accumulate</code></p></li><li class="listitem"><p><code class="code">inner_product</code></p></li><li class="listitem"><p><code class="code">partial_sum</code></p></li><li class="listitem"><p><code class="code">adjacent_difference</code></p></li></ul></div><p>Here is a simple example of the two forms of <code class="code">accumulate</code>.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">accumulate</code></p></li><li class="listitem"><p><code class="code">inner_product</code></p></li><li class="listitem"><p><code class="code">chapterial_sum</code></p></li><li class="listitem"><p><code class="code">adjacent_difference</code></p></li></ul></div><p>Here is a simple example of the two forms of <code class="code">accumulate</code>.
</p><pre class="programlisting">
int ar[50];
int someval = somefunction();
......@@ -26,4 +26,7 @@
and multiplies all the members of the array; here we must obviously
use 1 as a starting value instead of 0.
</p><p>The other three functions have similar dual-signature forms.
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Numerics
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......@@ -41,7 +41,7 @@ in <code class="code">sparc-sun-solaris2.8</code>. If the new directory is name
OS portion of the triplet (the default), then nothing needs to be changed.
</p><p>The first file to create in this directory, should be called
<code class="code">os_defines.h</code>. This file contains basic macro definitions
that are required to allow the C++ library to work with your C library.
that are required to allow the C++ library to work with your C library.
</p><p>Several libstdc++ source files unconditionally define the macro
<code class="code">_POSIX_SOURCE</code>. On many systems, defining this macro causes
large portions of the C library header files to be eliminated
......@@ -91,7 +91,7 @@ are exposing proper support for the related set of functions. If defined,
it must be 0 while bootstrapping the compiler/rebuilding the library.
</p><p>Finally, you should bracket the entire file in an include-guard, like
this:
</p><pre class="programlisting">
</p><pre class="programlisting">
#ifndef _GLIBCXX_OS_DEFINES
#define _GLIBCXX_OS_DEFINES
......@@ -131,7 +131,7 @@ upper-case, lower-case, alphabetic, etc. The <code class="code">ctype_base.h</c
file gives the type of the integer, and the values of the various bit
masks. You will have to peer at your own <code class="code">&lt;ctype.h&gt;</code> to figure out
how to define the values required by this file.
</p><p>The <code class="code">ctype_base.h</code> header file does not need include guards.
</p><p>The <code class="code">ctype_base.h</code> header file does not need include guards.
It should contain a single <code class="code">struct</code> definition called
<code class="code">ctype_base</code>. This <code class="code">struct</code> should contain two type
declarations, and one enumeration declaration, like this example, taken
......@@ -141,20 +141,20 @@ from the IRIX configuration:
{
typedef unsigned int mask;
typedef int* __to_type;
enum
{
space = _ISspace,
print = _ISprint,
cntrl = _IScntrl,
upper = _ISupper,
lower = _ISlower,
alpha = _ISalpha,
digit = _ISdigit,
punct = _ISpunct,
xdigit = _ISxdigit,
alnum = _ISalnum,
graph = _ISgraph
space = _ISspace,
print = _ISprint,
cntrl = _IScntrl,
upper = _ISupper,
lower = _ISlower,
alpha = _ISalpha,
digit = _ISdigit,
punct = _ISpunct,
xdigit = _ISxdigit,
alnum = _ISalnum,
graph = _ISgraph
};
};
</pre><p>The <code class="code">mask</code> type is the type of the elements in the table. If your
......@@ -176,14 +176,14 @@ function that must be written is the <code class="code">ctype&lt;char&gt;::ctype
constructor. Here is the IRIX example:
</p><pre class="programlisting">
ctype&lt;char&gt;::ctype(const mask* __table = 0, bool __del = false,
size_t __refs = 0)
size_t __refs = 0)
: _Ctype_nois&lt;char&gt;(__refs), _M_del(__table != 0 &amp;&amp; __del),
_M_toupper(NULL),
_M_tolower(NULL),
_M_ctable(NULL),
_M_table(!__table
? (const mask*) (__libc_attr._ctype_tbl-&gt;_class + 1)
: __table)
_M_toupper(NULL),
_M_tolower(NULL),
_M_ctable(NULL),
_M_table(!__table
? (const mask*) (__libc_attr._ctype_tbl-&gt;_class + 1)
: __table)
{ }
</pre><p>There are two parts of this that you might choose to alter. The first,
and most important, is the line involving <code class="code">__libc_attr</code>. That is
......@@ -199,7 +199,7 @@ lower-case, and vice versa. Here are the IRIX versions:
char
ctype&lt;char&gt;::do_toupper(char __c) const
{ return _toupper(__c); }
char
ctype&lt;char&gt;::do_tolower(char __c) const
{ return _tolower(__c); }
......@@ -215,21 +215,21 @@ machinery to do that on your system:
ctype&lt;char&gt;::do_toupper(char* __low, const char* __high) const
{
while (__low &lt; __high)
{
*__low = do_toupper(*__low);
++__low;
}
{
*__low = do_toupper(*__low);
++__low;
}
return __high;
}
const char*
ctype&lt;char&gt;::do_tolower(char* __low, const char* __high) const
{
while (__low &lt; __high)
{
*__low = do_tolower(*__low);
++__low;
}
{
*__low = do_tolower(*__low);
++__low;
}
return __high;
}
</pre><p>You must also provide the <code class="code">ctype_inline.h</code> file, which
......@@ -244,7 +244,7 @@ properties; they are analogous to the functions like <code class="code">isalpha<
ctype&lt;char&gt;::
is(mask __m, char __c) const throw()
{ return (_M_table)[(unsigned char)(__c)] &amp; __m; }
</pre><p>The <code class="code">_M_table</code> is the table passed in above, in the constructor.
</pre><p>The <code class="code">_M_table</code> is the table passed in above, in the constructor.
This is the table that contains the bitmasks for each character. The
implementation here should work on all systems.
</p><p>The next function is:
......@@ -254,7 +254,7 @@ implementation here should work on all systems.
is(const char* __low, const char* __high, mask* __vec) const throw()
{
while (__low &lt; __high)
*__vec++ = (_M_table)[(unsigned char)(*__low++)];
*__vec++ = (_M_table)[(unsigned char)(*__low++)];
return __high;
}
</pre><p>This function is similar; it copies the masks for all the characters
......@@ -267,16 +267,16 @@ from <code class="code">__low</code> up until <code class="code">__high</code> i
scan_is(mask __m, const char* __low, const char* __high) const throw()
{
while (__low &lt; __high &amp;&amp; !this-&gt;is(__m, *__low))
++__low;
++__low;
return __low;
}
const char*
ctype&lt;char&gt;::
scan_not(mask __m, const char* __low, const char* __high) const throw()
{
while (__low &lt; __high &amp;&amp; this-&gt;is(__m, *__low))
++__low;
++__low;
return __low;
}
</pre></div><div class="sect2" title="Thread Safety"><div class="titlepage"><div><div><h3 class="title"><a id="internals.thread_safety"></a>Thread Safety</h3></div></div></div><p>The C++ library string functionality requires a couple of atomic
......@@ -312,7 +312,7 @@ type, and two functions.
</p><p>The type is <code class="code">_Atomic_word</code>. Here is the version used on IRIX:
</p><pre class="programlisting">
typedef long _Atomic_word;
</pre><p>This type must be a signed integral type supporting atomic operations.
</pre><p>This type must be a signed integral type supporting atomic operations.
If you're using the OS approach, use the same type used by your system's
primitives. Otherwise, use the type for which your CPU provides atomic
primitives.
......@@ -327,7 +327,7 @@ must be equivalent to those provided here, but using atomic operations:
*__mem += __val;
return __result;
}
static inline void
__attribute__ ((__unused__))
__atomic_add (_Atomic_word* __mem, int __val)
......@@ -335,18 +335,18 @@ must be equivalent to those provided here, but using atomic operations:
*__mem += __val;
}
</pre></div><div class="sect2" title="Numeric Limits"><div class="titlepage"><div><div><h3 class="title"><a id="internals.numeric_limits"></a>Numeric Limits</h3></div></div></div><p>The C++ library requires information about the fundamental data types,
such as the minimum and maximum representable values of each type.
such as the minimum and maximum representable values of each type.
You can define each of these values individually, but it is usually
easiest just to indicate how many bits are used in each of the data
types and let the library do the rest. For information about the
macros to define, see the top of <code class="code">include/bits/std_limits.h</code>.
</p><p>If you need to define any macros, you can do so in <code class="code">os_defines.h</code>.
</p><p>If you need to define any macros, you can do so in <code class="code">os_defines.h</code>.
However, if all operating systems for your CPU are likely to use the
same values, you can provide a CPU-specific file instead so that you
do not have to provide the same definitions for each operating system.
do not have to provide the same definitions for each operating system.
To take that approach, create a new file called <code class="code">cpu_limits.h</code> in
your CPU configuration directory (see <a class="link" href="internals.html#internals.cpu" title="CPU">CPU</a>).
</p></div><div class="sect2" title="Libtool"><div class="titlepage"><div><div><h3 class="title"><a id="internals.libtool"></a>Libtool</h3></div></div></div><p>The C++ library is compiled, archived and linked with libtool.
</p></div><div class="sect2" title="Libtool"><div class="titlepage"><div><div><h3 class="title"><a id="internals.libtool"></a>Libtool</h3></div></div></div><p>The C++ library is compiled, archived and linked with libtool.
Explaining the full workings of libtool is beyond the scope of this
document, but there are a few, particular bits that are necessary for
porting.
......
......@@ -5,5 +5,5 @@
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See the <a class="link" href="ext_io.html" title="Chapter 39. Input and Output">extensions</a> for using
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See the <a class="link" href="ext_io.html" title="Chapter 26. Input and Output">extensions</a> for using
<span class="type">FILE</span> and <span class="type">file descriptors</span> with
<code class="classname">ofstream</code> and
<code class="classname">ifstream</code>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt11ch27s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="io.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt11ch28s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Binary Input and Output </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Performance</td></tr></table></div></body></html>
</p></div><div class="sect2" title="Performance"><div class="titlepage"><div><div><h3 class="title"><a id="std.io.c.sync"></a>Performance</h3></div></div></div><p>
Pathetic Performance? Ditch C.
</p><p>It sounds like a flame on C, but it isn't. Really. Calm down.
I'm just saying it to get your attention.
</p><p>Because the C++ library includes the C library, both C-style and
C++-style I/O have to work at the same time. For example:
</p><pre class="programlisting">
#include &lt;iostream&gt;
#include &lt;cstdio&gt;
std::cout &lt;&lt; "Hel";
std::printf ("lo, worl");
std::cout &lt;&lt; "d!\n";
</pre><p>This must do what you think it does.
</p><p>Alert members of the audience will immediately notice that buffering
is going to make a hash of the output unless special steps are taken.
</p><p>The special steps taken by libstdc++, at least for version 3.0,
involve doing very little buffering for the standard streams, leaving
most of the buffering to the underlying C library. (This kind of
thing is tricky to get right.)
The upside is that correctness is ensured. The downside is that
writing through <code class="code">cout</code> can quite easily lead to awful
performance when the C++ I/O library is layered on top of the C I/O
library (as it is for 3.0 by default). Some patches have been applied
which improve the situation for 3.1.
</p><p>However, the C and C++ standard streams only need to be kept in sync
when both libraries' facilities are in use. If your program only uses
C++ I/O, then there's no need to sync with the C streams. The right
thing to do in this case is to call
</p><pre class="programlisting">
#include <span class="emphasis"><em>any of the I/O headers such as ios, iostream, etc</em></span>
std::ios::sync_with_stdio(false);
</pre><p>You must do this before performing any I/O via the C++ stream objects.
Once you call this, the C++ streams will operate independently of the
(unused) C streams. For GCC 3.x, this means that <code class="code">cout</code> and
company will become fully buffered on their own.
</p><p>Note, by the way, that the synchronization requirement only applies to
the standard streams (<code class="code">cin</code>, <code class="code">cout</code>,
<code class="code">cerr</code>,
<code class="code">clog</code>, and their wide-character counterchapters). File stream
objects that you declare yourself have no such requirement and are fully
buffered.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="fstreams.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="io.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="atomics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">File Based Streams </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 14. 
Atomics
</td></tr></table></div></body></html>
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 24. Iostream Objects</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="io.html" title="Part XI.  Input and Output" /><link rel="prev" href="io.html" title="Part XI.  Input and Output" /><link rel="next" href="streambufs.html" title="Chapter 25. Stream Buffers" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 24. Iostream Objects</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="io.html">Prev</a> </td><th width="60%" align="center">Part XI. 
Input and Output
</th><td width="20%" align="right"> <a accesskey="n" href="streambufs.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 24. Iostream Objects"><div class="titlepage"><div><div><h2 class="title"><a id="manual.io.objects"></a>Chapter 24. Iostream Objects</h2></div></div></div><p>To minimize the time you have to wait on the compiler, it's good to
only include the headers you really need. Many people simply include
&lt;iostream&gt; when they don't need to -- and that can <span class="emphasis"><em>penalize
your runtime as well.</em></span> Here are some tips on which header to use
for which situations, starting with the simplest.
</p><p><span class="emphasis"><em>&lt;iosfwd&gt;</em></span> should be included whenever you simply
need the <span class="emphasis"><em>name</em></span> of an I/O-related class, such as
"ofstream" or "basic_streambuf". Like the name
implies, these are forward declarations. (A word to all you fellow
old school programmers: trying to forward declare classes like
"class istream;" won't work. Look in the iosfwd header if
you'd like to know why.) For example,
</p><pre class="programlisting">
#include &lt;iosfwd&gt;
class MyClass
{
....
std::ifstream&amp; input_file;
};
extern std::ostream&amp; operator&lt;&lt; (std::ostream&amp;, MyClass&amp;);
</pre><p><span class="emphasis"><em>&lt;ios&gt;</em></span> declares the base classes for the entire
I/O stream hierarchy, std::ios_base and std::basic_ios&lt;charT&gt;, the
counting types std::streamoff and std::streamsize, the file
positioning type std::fpos, and the various manipulators like
std::hex, std::fixed, std::noshowbase, and so forth.
</p><p>The ios_base class is what holds the format flags, the state flags,
and the functions which change them (setf(), width(), precision(),
etc). You can also store extra data and register callback functions
through ios_base, but that has been historically underused. Anything
which doesn't depend on the type of characters stored is consolidated
here.
</p><p>The template class basic_ios is the highest template class in the
hierarchy; it is the first one depending on the character type, and
holds all general state associated with that type: the pointer to the
polymorphic stream buffer, the facet information, etc.
</p><p><span class="emphasis"><em>&lt;streambuf&gt;</em></span> declares the template class
basic_streambuf, and two standard instantiations, streambuf and
wstreambuf. If you need to work with the vastly useful and capable
stream buffer classes, e.g., to create a new form of storage
transport, this header is the one to include.
</p><p><span class="emphasis"><em>&lt;istream&gt;</em></span>/<span class="emphasis"><em>&lt;ostream&gt;</em></span> are
the headers to include when you are using the &gt;&gt;/&lt;&lt;
interface, or any of the other abstract stream formatting functions.
For example,
</p><pre class="programlisting">
#include &lt;istream&gt;
std::ostream&amp; operator&lt;&lt; (std::ostream&amp; os, MyClass&amp; c)
{
return os &lt;&lt; c.data1() &lt;&lt; c.data2();
}
</pre><p>The std::istream and std::ostream classes are the abstract parents of
the various concrete implementations. If you are only using the
interfaces, then you only need to use the appropriate interface header.
</p><p><span class="emphasis"><em>&lt;iomanip&gt;</em></span> provides "extractors and inserters
that alter information maintained by class ios_base and its derived
classes," such as std::setprecision and std::setw. If you need
to write expressions like <code class="code">os &lt;&lt; setw(3);</code> or
<code class="code">is &gt;&gt; setbase(8);</code>, you must include &lt;iomanip&gt;.
</p><p><span class="emphasis"><em>&lt;sstream&gt;</em></span>/<span class="emphasis"><em>&lt;fstream&gt;</em></span>
declare the six stringstream and fstream classes. As they are the
standard concrete descendants of istream and ostream, you will already
know about them.
</p><p>Finally, <span class="emphasis"><em>&lt;iostream&gt;</em></span> provides the eight standard
global objects (cin, cout, etc). To do this correctly, this header
also provides the contents of the &lt;istream&gt; and &lt;ostream&gt;
headers, but nothing else. The contents of this header look like
</p><pre class="programlisting">
#include &lt;ostream&gt;
#include &lt;istream&gt;
namespace std
{
extern istream cin;
extern ostream cout;
....
// this is explained below
<span class="emphasis"><em>static ios_base::Init __foo;</em></span> // not its real name
}
</pre><p>Now, the runtime penalty mentioned previously: the global objects
must be initialized before any of your own code uses them; this is
guaranteed by the standard. Like any other global object, they must
be initialized once and only once. This is typically done with a
construct like the one above, and the nested class ios_base::Init is
specified in the standard for just this reason.
</p><p>How does it work? Because the header is included before any of your
code, the <span class="emphasis"><em>__foo</em></span> object is constructed before any of
your objects. (Global objects are built in the order in which they
are declared, and destroyed in reverse order.) The first time the
constructor runs, the eight stream objects are set up.
</p><p>The <code class="code">static</code> keyword means that each object file compiled
from a source file containing &lt;iostream&gt; will have its own
private copy of <span class="emphasis"><em>__foo</em></span>. There is no specified order
of construction across object files (it's one of those pesky NP
problems that make life so interesting), so one copy in each object
file means that the stream objects are guaranteed to be set up before
any of your code which uses them could run, thereby meeting the
requirements of the standard.
</p><p>The penalty, of course, is that after the first copy of
<span class="emphasis"><em>__foo</em></span> is constructed, all the others are just wasted
processor time. The time spent is merely for an increment-and-test
inside a function call, but over several dozen or hundreds of object
files, that time can add up. (It's not in a tight loop, either.)
</p><p>The lesson? Only include &lt;iostream&gt; when you need to use one of
the standard objects in that source file; you'll pay less startup
time. Only include the header files you need to in general; your
compile times will go down when there's less parsing work to do.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="io.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="io.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="streambufs.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part XI. 
Input and Output
 </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 25. Stream Buffers</td></tr></table></div></body></html>
......@@ -2,7 +2,7 @@
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>License</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="status.html" title="Chapter 1. Status" /><link rel="prev" href="status.html" title="Chapter 1. Status" /><link rel="next" href="bugs.html" title="Bugs" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">License</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="status.html">Prev</a> </td><th width="60%" align="center">Chapter 1. Status</th><td width="20%" align="right"> <a accesskey="n" href="bugs.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="License"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.status.license"></a>License</h2></div></div></div><p>
There are two licenses affecting GNU libstdc++: one for the code,
and one for the documentation.
and one for the documentation.
</p><p>
There is a license section in the FAQ regarding common <a class="link" href="../faq.html#faq.license" title="License">questions</a>. If you have more
questions, ask the FSF or the <a class="ulink" href="http://gcc.gnu.org/lists.html" target="_top">gcc mailing list</a>.
......@@ -94,7 +94,7 @@ requirements of the license of GCC.<br />
<a class="link" href="appendix_gfdl.html" title="Appendix E. GNU Free Documentation License"> GNU Free Documentation
License version 1.2</a>. There are no Front-Cover Texts, no
Back-Cover Texts, and no Invariant Sections.
</p><p>
</p><p>
For documentation generated by doxygen or other automated tools
via processing source code comments and markup, the original source
code license applies to the generated files. Thus, the doxygen
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