basic_ios.tcc (basic_ios::init): Set _M_fill to zero.

2002-02-26  Benjamin Kosnik  <bkoz@redhat.com>

	* include/bits/basic_ios.tcc (basic_ios::init): Set _M_fill to zero.
	Adjust comment.
	* include/bits/basic_ios.h (basic_ios::_M_fill): Make mutable.
	(basic_ios::_M_fill_init): New.
	(basic_ios::fill()): Deal with _M_fill lazily.
	Adjust comment.
	* testsuite/27_io/ios_init.cc (test02): Adjust testcase.

From-SVN: r50076

libstdc++-v3/ChangeLog

+2002-02-26  Benjamin Kosnik  <bkoz@redhat.com>
+
+	* include/bits/basic_ios.tcc (basic_ios::init): Set _M_fill to zero.
+	Adjust comment.
+	* include/bits/basic_ios.h (basic_ios::_M_fill): Make mutable.
+	(basic_ios::_M_fill_init): New.
+	(basic_ios::fill()): Deal with _M_fill lazily.
+	Adjust comment. 
+	* testsuite/27_io/ios_init.cc (test02): Adjust testcase.
+
 2002-02-26  Loren Rittle  <ljrittle@acm.org>
 
 	* include/Makefile.am (thread_target_headers): Unconditionally

libstdc++-v3/include/bits/basic_ios.h

@@ -64,7 +64,8 @@ namespace std
       // Data members:
     protected:
       basic_ostream<_CharT, _Traits>* 	_M_tie;
-      char_type 			_M_fill;
+      mutable char_type 		_M_fill;
+      mutable bool			_M_fill_init;
       iostate 				_M_exception;
 
       basic_streambuf<_CharT, _Traits>* _M_streambuf;
@@ -160,7 +161,14 @@ namespace std
 
       char_type 
       fill() const 
-      { return _M_fill; }
+      {
+	if (!_M_fill_init)
+	  {
+	    _M_fill = this->widen(' ');
+	    _M_fill_init = true;
+	  }
+	return _M_fill; 
+      }
 
       char_type 
       fill(char_type __ch)

libstdc++-v3/include/bits/basic_ios.tcc

@@ -144,17 +144,20 @@ namespace std
       _M_cache_facets(_M_ios_locale);
       _M_tie = 0;
 
-      // NB: The 27.4.4.1 Postconditions Table only specifies
-      // requirements after basic_ios::init() has been called. As part
-      // of this, fill() must return widen(' '), which needs an imbued
-      // ctype facet of char_type to return without throwing an
-      // exception. Unfortunately, ctype<char_type> is not necessarily a
-      // required facet, so streams with char_type != [char, wchar_t]
-      // will not have it by default. However, because fill()'s
-      // signature is const, this data member cannot be lazily
-      // initialized.  Thus, thoughts of using a non-const helper
-      // function in ostream inserters is really besides the point.
-      _M_fill = this->widen(' ');
+      // NB: The 27.4.4.1 Postconditions Table specifies requirements
+      // after basic_ios::init() has been called. As part of this,
+      // fill() must return widen(' ') any time after init() has been
+      // called, which needs an imbued ctype facet of char_type to
+      // return without throwing an exception. Unfortunately,
+      // ctype<char_type> is not necessarily a required facet, so
+      // streams with char_type != [char, wchar_t] will not have it by
+      // default. Because of this, the correct value for _M_fill is
+      // constructed on the first call of fill(). That way,
+      // unformatted input and output with non-required basic_ios
+      // instantiations is possible even without imbuing the expected
+      // ctype<char_type> facet.
+      _M_fill = 0;
+      _M_fill_init = false;
 
       _M_exception = goodbit;
       _M_streambuf = __sb;

libstdc++-v3/testsuite/27_io/ios_init.cc

@@ -83,10 +83,8 @@ void test01()
 }
 
 // Non-required instantiations don't have the required facets inbued,
-// by default, into the locale object. As such, basic_ios::init is
-// required to return a bad_cast for the first use of fill() call.
+// by default, into the locale object.
 // See 27.4.4.1
-
 class gnu_ios: public std::basic_ios<char> { };
 
 void test02() 
@@ -94,6 +92,7 @@ void test02()
   bool test = true;
 
   // 01: Doesn't call basic_ios::init, which uses ctype<char_type>..
+  // This should be unambiguously correct.
   try
     {
       gnu_ios gios;
@@ -103,15 +102,12 @@ void test02()
       test = false; 
     }
 
-  // 02: Calls basic_ios::init, which uses ctype<char_type>..
+  // 02: Calls basic_ios::init, which may call ctype<char_type>...
   try
     {
       std::basic_string<unsigned short>        	str;
       std::basic_ostringstream<unsigned short> 	oss(str);
       
-      // Shouldn't get this far.
-      test = false; 
-
       // Try each member functions for unformatted io.
       // put
       oss.put(324);
@@ -125,7 +121,9 @@ void test02()
     }
   catch(const std::bad_cast& obj)
     {
-      // This is correct.
+      // Should be able to do the above without calling fill() and
+      // forcing a call to widen...
+      test = false;
     }
   catch(...)
     {