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explanations.html: New file. 

2001-07-09  Phil Edwards  <pme@sources.redhat.com>

	* docs/html/explanations.html:  New file.
	* docs/html/configopts.html:  Link to it to provide more notes
	on cstdio.  Minor markup and spacing fixes.
	* docs/html/27_io/howto.html:  Talk about sync_with_stdio.

From-SVN: r43868
parent 2b2c8b3e
Showing with 177 additions and 45 deletions
libstdc++-v3/ChangeLog
2001-07-09 Phil Edwards <pme@sources.redhat.com>
* docs/html/explanations.html: New file.
* docs/html/configopts.html: Link to it to provide more notes
on cstdio. Minor markup and spacing fixes.
* docs/html/27_io/howto.html: Talk about sync_with_stdio.
2001-07-09 Kriang Lerdsuwanakij <lerdsuwa@users.sourceforge.net>
* include/bits/valarray_meta.h (_Expr::operator+): Use qualified id
......
libstdc++-v3/docs/html/27_io/howto.html
......@@ -8,7 +8,7 @@
<META NAME="GENERATOR" CONTENT="vi and eight fingers">
<TITLE>libstdc++-v3 HOWTO: Chapter 27</TITLE>
<LINK REL=StyleSheet HREF="../lib3styles.css">
<!-- $Id: howto.html,v 1.4 2001/04/03 00:26:56 pme Exp $ -->
<!-- $Id: howto.html,v 1.5 2001/05/30 21:55:03 pme Exp $ -->
</HEAD>
<BODY>
......@@ -29,6 +29,7 @@
<LI><A HREF="#5">What is this &lt;sstream&gt;/stringstreams thing?</A>
<LI><A HREF="#6">Deriving a stream buffer</A>
<LI><A HREF="#7">More on binary I/O</A>
<LI><A HREF="#8">Pathetic performance? Ditch C.</A>
</UL>
<HR>
......@@ -400,14 +401,65 @@
a portable binary format.
</P>
<HR>
<H2><A NAME="8">Pathetic performance? Ditch C.</A></H2>
<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:
<PRE>
#include &lt;iostream&gt;
#include &lt;cstdio&gt;
std::cout &lt;&lt; &quot;Hel&quot;;
std::printf (&quot;lo, worl&quot;);
std::cout &lt;&lt; &quot;d!\n&quot;;
</PRE>
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 <A HREF="../explanations.html#cstdio">tricky to get right</A>.)
The upside is that correctness is insured. The downside is that
writing through <TT>cout</TT> 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 are in the
works which should 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
<PRE>
#include <EM>any of the I/O headers such as ios, iostream, etc</EM>
std::sync_with_stdio(false);
</PRE>
</P>
<P>You must do this before performing any I/O via the C++ stream objects.
Once you call this, the C++ streams will operate independantly of the
(unused) C streams. For GCC 3.0, this means that <TT>cout</TT> 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 (cin, cout, cerr, clog, and thier wide-character
counterparts). File stream objects that you create yourself have no
such requirement and are fully buffered.
</P>
<!-- ####################################################### -->
<HR>
<HR><BR><BR><BR><BR><BR><BR><BR><BR>
<P CLASS="fineprint"><EM>
Comments and suggestions are welcome, and may be sent to
<A HREF="mailto:libstdc++@gcc.gnu.org">the mailing list</A>.
<BR> $Id: howto.html,v 1.4 2001/04/03 00:26:56 pme Exp $
<BR> $Id: howto.html,v 1.5 2001/05/30 21:55:03 pme Exp $
</EM></P>
......
libstdc++-v3/docs/html/configopts.html
......@@ -7,7 +7,7 @@
<META NAME="GENERATOR" CONTENT="vi and eight fingers">
<TITLE>libstdc++-v3 configure options</TITLE>
<LINK REL=StyleSheet HREF="lib3styles.css">
<!-- $Id: configopts.html,v 1.9 2001/04/06 01:47:11 bkoz Exp $ -->
<!-- $Id: configopts.html,v 1.10 2001/04/20 08:59:25 bkoz Exp $ -->
</HEAD>
<BODY>
......@@ -66,56 +66,55 @@ options</A></H1>
I/O package (from
<A HREF="http://sources.redhat.com/glibc/">glibc</A>, the
GNU C library), or 'stdio' to use a generic &quot;C&quot;
abstraction. The default is 'stdio'.
abstraction. The default is 'stdio'. A longer explanation
is <A HREF="explanations.html#cstdio">here</A>.
</P>
<DT><TT>--enable-sjlj-exceptions </TT>
<DD><P> Forces old, short-jump/long-jump exception handling model. If
at all possible, the new, frame unwinding exception handling routines
should be used instead, as they significantly reduce both runtime
memory usage and executable size.
<DT><TT>--enable-sjlj-exceptions </TT>
<DD><P>Forces old, short-jump/long-jump exception handling model. If
at all possible, the new, frame unwinding exception handling routines
should be used instead, as they significantly reduce both runtime
memory usage and executable size.
</P>
<DT><TT>--enable-clocale </TT>
<DD><P>This is an abbreviated form of <TT>'--enable-clocale=generic'</TT>
(described next).
</P>
<DT><TT>--enable-clocale=MODEL </TT> <DD><P>Select a target-specific
underlying locale package. The choices are 'gnu' to specify an X/Open
(IEEE Std. 1003.1-200x) model based on langinfo/iconv (from <A
HREF="http://sources.redhat.com/glibc/">glibc</A>, the GNU C
library), or 'generic' to use a generic &quot;C&quot; abstraction
which consists of &quot;C&quot; locale info. The default is
'generic'.
<DT><TT>--enable-clocale=MODEL </TT>
<DD><P>Select a target-specific underlying locale package. The choices
are 'gnu' to specify an X/Open (IEEE Std. 1003.1-200x) model based
on langinfo/iconv (from
<A HREF="http://sources.redhat.com/glibc/">glibc</A>, the GNU C
library), or 'generic' to use a generic &quot;C&quot; abstraction
which consists of &quot;C&quot; locale info. The default is 'generic'.
</P>
<DT><TT>--enable-c99 </TT>
<DD><P>The &quot;long long&quot; type was introduced in C99, along
with bunches of other functions for wide characters, and math
classification macros, etc. If enabled, all C99 functions not
specified by the C++ standard will be put into namespace c99,
and then all names in the c99 namespace will be injected into
namespace std, so that C99 functions can be used "as if" they
were in the C++ standard (as they will eventually be in some
future revision of the standard, without a doubt.) By default,
C99 support is on, assuming the configure probes find all the
necessary functions and bits necessary.
with bunches of other functions for wide characters, and math
classification macros, etc. If enabled, all C99 functions not
specified by the C++ standard will be put into <TT>namespace
c99</TT>, and then all names in the c99 namespace will be injected
into namespace std, so that C99 functions can be used &quot;as
if&quot; they were in the C++ standard (as they will eventually
be in some future revision of the standard, without a doubt).
By default, C99 support is on, assuming the configure probes find
all the necessary functions and bits necessary.
</P>
<DT><TT>--enable-long-long </TT>
<DD><P>The &quot;long long&quot; type was introduced in C99. It is
provided as a GNU extension to C++98 in g++. This flag builds
support for &quot;long long&quot; into the library
(specialized templates and the like for iostreams). This
option is on by default: if enabled, users will have to either
use the new-style &quot;C&quot; headers by default (ie cmath
not math.h) or add appropriate compile-time flags to all
compile lines to allow &quot;C&quot; visibility of this
feature (on GNU/Linux, the flag is -D_ISOC99_SOURCE, which is
added automatically via CPLUSPLUS_CPP_SPEC's addition of
_GNU_SOURCE).
support for &quot;long long&quot; into the library (specialized
templates and the like for iostreams). This option is on by default:
if enabled, users will have to either use the new-style &quot;C&quot;
headers by default (i.e., &lt;cmath&gt; not &lt;math.h&gt;)
or add appropriate compile-time flags to all compile lines to
allow &quot;C&quot; visibility of this feature (on GNU/Linux,
the flag is -D_ISOC99_SOURCE, which is added automatically via
CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
</P>
<DT><TT>--enable-cheaders=OPTION </TT>
......@@ -148,14 +147,14 @@ options</A></H1>
<DT><TT>--enable-version-specific-runtime-libs </TT>
<DD><P>Specify that run-time libraries should be installed in the
compiler-specific subdirectory (i.e.,
<TT>$(libdir)/gcc-lib/$(target_alias)/$(gcc_version)</TT>)
instead of <TT>$(libdir)</TT>. This option is useful if you
intend to use several versions of gcc in parallel. In addition,
libstdc++'s include files will be installed in
<TT>$(libdir)/gcc-lib/$(target_alias)/$(gcc_version)/include/g++</TT>,
unless you also specify
<TT>--with-gxx-include-dir=_dirname_</TT> during configuration.
compiler-specific subdirectory (i.e.,
<TT>${libdir}/gcc-lib/${target_alias}/${gcc_version}</TT>)
instead of <TT>${libdir}</TT>. This option is useful if you
intend to use several versions of gcc in parallel. In addition,
libstdc++'s include files will be installed in
<TT>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</TT>,
unless you also specify
<TT>--with-gxx-include-dir=<EM>dirname</EM></TT> during configuration.
</P>
<DT><TT>--with-gxx-include-dir=&lt;include-files dir&gt;</TT>
......@@ -212,7 +211,7 @@ options</A></H1>
<HR>
<P CLASS="fineprint"><EM>
$Id: configopts.html,v 1.9 2001/04/06 01:47:11 bkoz Exp $
$Id: configopts.html,v 1.10 2001/04/20 08:59:25 bkoz Exp $
</EM></P>
......
libstdc++-v3/docs/html/explanations.html 0 → 100644
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
<HEAD>
<META NAME="AUTHOR" CONTENT="pme@sources.redhat.com (Phil Edwards)">
<META NAME="KEYWORDS" CONTENT="libstdc++, libstdc++-v3, GCC, g++">
<META NAME="DESCRIPTION" CONTENT="Explanatory notes about libstdc++-v3.">
<META NAME="GENERATOR" CONTENT="vi and eight fingers">
<TITLE>Explanatory notes about libstdc++-v3 design</TITLE>
<LINK REL=StyleSheet HREF="lib3styles.css">
<!-- $Id: configopts.html,v 1.10 2001/04/20 08:59:25 bkoz Exp $ -->
</HEAD>
<BODY>
<H1 CLASS="centered"><A NAME="top">Explanatory notes about libstdc++-v3
design</A></H1>
<P>The latest version of this document is always available at
<A HREF="http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html">
http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html</A>.
</P>
<P>To the <A HREF="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</A>.
<!-- ####################################################### -->
<HR>
<A NAME="cstdio"><H3>&quot;I/O packages&quot;, <TT>--enable-cstdio</TT></H3></A>
<P>In addition to all the nifty things which C++ can do for I/O, its library
also includes all of the I/O capabilites of C. Making them work together
can be a challenge, not only
<A HREF="27_io/howto.html#8">for the programmer</A> but for the
implementors as well.
</P>
<P>There are two ways to do a C++ library: the cool way, and the easy way.
More specifically, the cool-but-easy-to-get-wrong way, and the
easy-to-guarantee-correct-behavior way. For 3.0, the easy way is used.
</P>
<P>Choosing 'stdio' is the easy way. It builds a C++ library which forwards
all operations to the C library. Many of the C++ I/O functions are
specified in the standard 'as if' they called a certain C function; the
easiest way to get it correct is to actually call that function. The
disadvantage is that the C++ code will run slower (fortunately, the layer
is thin).
</P>
<P>Choosing 'libio' is the cool way; it allows C++ and C to share some
buffers. It's disabled because of tricky synchronization issues. Other
cool ways (various methods of sharing resources between C and C++
facilities, instead of layering) are possible. This approach can speed
up I/O significantly.
</P>
<P>Other packages are possible. For a new package, a header must be
written to provide types like streamsize (usually just a typedef), as
well as some internal types like<TT> __c_file_type </TT> and
<TT> __c_lock </TT> (for the stdio case, these are FILE (as in
&quot;FILE*&quot;) and a simple POSIX mutex, respectively). An
interface class called <TT> __basic_file </TT> must also be filled in;
as an example, for the stdio case, these member functions are all
inline calles to fread, fwrite, etc.
</P>
<P>Return <A HREF="#top">to the top of the page</A> or
<A HREF="http://gcc.gnu.org/libstdc++/">to the homepage</A>.
</P>
<!-- ####################################################### -->
<HR>
<P CLASS="fineprint"><EM>
$Id$
</EM></P>
</BODY>
</HTML>
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