This is the mail archive of the gcc-prs@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

libstdc++/9659: 3.3/3.4 seekoff overload problem with optimization


>Number:         9659
>Category:       libstdc++
>Synopsis:       3.3/3.4 seekoff overload problem with optimization
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Tue Feb 11 10:26:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     scott snyder
>Release:        3.4 20030210 (experimental)
>Organization:
<organization of PR author (multiple lines)>
>Environment:
System: Linux karma 2.4.19-emp_2419p5a829i #1 Tue Sep 3 17:42:17 EST 2002 i686 unknown
Architecture: i686

	<machine, os, target, libraries (multiple lines)>
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: ../gcc/configure --prefix=/usr/local/gcc --enable-threads=posix --enable-long-long
>Description:

When the source below is compiled with -O3, i get the following errors:

$ g++ -c -O3 x.cc
/usr/local/gcc/include/c++/3.4/bits/fstream.tcc: In member function `typename 
   std::basic_filebuf<_CharT, _Traits>::pos_type std::basic_filebuf<_CharT, 
   _Traits>::seekoff(typename _Traits::off_type, std::_Ios_Seekdir, 
   std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]':
/usr/local/gcc/include/c++/3.4/bits/fstream.tcc:104:   instantiated from `typename std::basic_filebuf<_CharT, _Traits>::__filebuf_type* std::basic_filebuf<_CharT, _Traits>::open(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]'
/usr/local/gcc/include/c++/3.4/fstream:564:   instantiated from `void std::basic_ifstream<_CharT, _Traits>::open(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]'
/usr/local/gcc/include/c++/3.4/fstream:520:   instantiated from `std::basic_ifstream<_CharT, _Traits>::basic_ifstream(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]'
x.cc:9:   instantiated from here
/usr/local/gcc/include/c++/3.4/bits/fstream.tcc:460: error: ambiguous overload 
   for `std::streampos& + char* const&' operator
/usr/local/gcc/include/c++/3.4/bits/fstream.tcc:460: error: candidates are: 
   operator+(int, char*) <built-in>
/usr/local/gcc/include/c++/3.4/bits/fpos.h:90: error:                 
   std::fpos<_StateT> std::fpos<_StateT>::operator+(long int) [with _StateT = 
   mbstate_t] <near match>
x.cc:6: error:                 TString operator+(long int, const TString&)
$

It's a bit strange, because if -O2 or below is used, the error goes away.
Is the built-in operator mentioned in the error message visible only
if -O3 is used?

I see this problem both with 3.3 and 3.4.

It seems to be related to the patch for libstdc++/9439 and
libstdc++/9425 that was introduced recently.  In fact,
if i rewrite the part of that patch where this error
is occuring to use += rather than +:


Index: fstream.tcc
===================================================================
RCS file: /cvsroot/gcc/gcc/libstdc++-v3/include/bits/fstream.tcc,v
retrieving revision 1.47
diff -u -p -c -r1.47 fstream.tcc
*** fstream.tcc	4 Feb 2003 22:42:32 -0000	1.47
--- fstream.tcc	11 Feb 2003 09:54:38 -0000
*************** namespace std
*** 455,464 ****
  	    {
  	      pos_type __tmp =
  		_M_file.seekoff(__off, ios_base::cur, __mode);
! 	      if (__tmp >= 0)
  		// Seek successful.
! 		__ret = __tmp +
! 		  std::max(this->_M_out_cur, this->_M_in_cur) - _M_filepos;
  	    }
  	}
        _M_last_overflowed = false;	
--- 455,465 ----
  	    {
  	      pos_type __tmp =
  		_M_file.seekoff(__off, ios_base::cur, __mode);
! 	      if (__tmp >= 0) {
  		// Seek successful.
!                 __ret = __tmp;
!                 __ret += std::max(this->_M_out_cur, this->_M_in_cur) - _M_filepos;
!               }		  
  	    }
  	}
        _M_last_overflowed = false;	


then the error goes away.


>How-To-Repeat:

Compile with -O3:

----------------------
#include <fstream>

struct TString {
  TString(const char *s);
};
TString operator+(long i, const TString& s);

void is_new(const char* f) {
  std::ifstream test(f,std::ios::in);
}
----------------------

>Fix:
See above.

>Release-Note:
>Audit-Trail:
>Unformatted:


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]