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Date: Thu, 13 Feb 2003 21:46:00 -0000
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To: paolo@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
From: Paolo Carlini <pcarlini@unitus.it>
Subject: Re: libstdc++/9580: basic_filebuf<> with custom traits_type fails
 to link
Reply-To: Paolo Carlini <pcarlini@unitus.it>
X-SW-Source: 2003-02/txt/msg00597.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR libstdc++/9580; it has been noted by GNATS.

From: Paolo Carlini <pcarlini@unitus.it>
To: Gabriel Dos Reis <gdr@integrable-solutions.net>
Cc: gcc-gnats@gcc.gnu.org,  peturr02@ru.is,  gcc-bugs@gcc.gnu.org
Subject: Re: libstdc++/9580: basic_filebuf<> with custom traits_type fails
 to link
Date: Thu, 13 Feb 2003 22:40:15 +0100

 Gabriel Dos Reis wrote:
 
 >If I recall correctly, this change was made because of some
 >differences in the way a narrow character stream based on
 >char_traits<char> behaves and the way the general Traits may behave.
 >At that point, I seem to recall that the goal was to have a general
 >implementation  of that function plus the special case.  I'll have to
 >go back and check my logs, unless Benjamin has a better recollection. 
 >
 Thanks Gaby. Well, I'd like to ask a little bit more help. Perhaps we are
 on the right track.
 
 The complete error message at link time is the following:
 
 /tmp/ccVSVF9A.o: In function `std::basic_filebuf<char, 
 MyTraits>::underflow()':
 /tmp/ccVSVF9A.o(.gnu.linkonce.t._ZNSt13basic_filebufIc8MyTraitsE9underflowEv+0x15): 
 undefined reference to `std::basic_filebuf<char, 
 MyTraits>::_M_underflow_common(bool)'
 /tmp/ccVSVF9A.o: In function `std::basic_filebuf<char, MyTraits>::uflow()':
 /tmp/ccVSVF9A.o(.gnu.linkonce.t._ZNSt13basic_filebufIc8MyTraitsE5uflowEv+0x15): 
 undefined reference to `std::basic_filebuf<char, 
 MyTraits>::_M_underflow_common(bool)'
 
 As you can see, underflow and uflow are missing the generic 
 _M_underflow_common.
 
 Now, in the current std_fstream.h there is:
 
   // Explicit specialization declarations, defined in src/fstream.cc.
   template<>
     basic_filebuf<char>::int_type
     basic_filebuf<char>::_M_underflow_common(bool __bump);
 
  #ifdef _GLIBCPP_USE_WCHAR_T
   template<>
     basic_filebuf<wchar_t>::int_type
     basic_filebuf<wchar_t>::_M_underflow_common(bool __bump);
  #endif
 
   // Generic definitions.
   template <typename _CharT, typename _Traits>
     typename basic_filebuf<_CharT, _Traits>::int_type
     basic_filebuf<_CharT, _Traits>::underflow()
     { return _M_underflow_common(false); }
 
   template <typename _CharT, typename _Traits>
     typename basic_filebuf<_CharT, _Traits>::int_type
     basic_filebuf<_CharT, _Traits>::uflow()
     { return _M_underflow_common(true); }
 
 Naively, something seems suspect here: the *generic* underflow and uflow 
 are still there!!
 
 Shouldn't they be disposed too, for the time being, at least?
 Paolo.