[Bug c++/15645] New: stringstream/ostream/iomanip memory scribble bug

["andrew at walrond dot org" <gcc-bugzilla at gcc dot gnu dot org>]

This bug causes a segfault in my full application.This testcase does not crash, 
but it does cause Valgrind to complain. 
 
Testcase built with "gcc -lstdc++ test.cpp": 
 
        #include <sstream> 
        #include <iomanip> 
        using namespace std; 
 
        int main() 
        { 
                 ostringstream oss; 
                 oss << internal << setw(2) << 0; 
        } 
 
Interestingly, the '0' triggers the behaviour. Substitute a non-zero number and 
it runs without incident. 
 
andrew@bob andrew $ valgrind --tool=memcheck a.out 
==296== Memcheck, a memory error detector for x86-linux. 
==296== Copyright (C) 2002-2004, and GNU GPL'd, by Julian Seward. 
==296== Using valgrind-2.1.1, a program supervision framework for x86-linux. 
==296== Copyright (C) 2000-2004, and GNU GPL'd, by Julian Seward. 
==296== For more details, rerun with: -v 
==296== 
==296== Conditional jump or move depends on uninitialised value(s) 
==296==    at 0x3C07D9A6: std::__pad<char, std::char_traits<char> 
>::_S_pad(std::ios_base&, char, char*, char const*, int, int, bool) 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296==    by 0x3C07DA83: std::num_put<char, std::ostreambuf_iterator<char, 
std::char_traits<char> > >::_M_pad(char, int, std::ios_base&, char*, char 
const*, int&) const 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296==    by 0x3C07E94A: std::ostreambuf_iterator<char, std::char_traits<char> 
> std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > 
>::_M_convert_int<long>(std::ostreambuf_iterator<char, std::char_traits<char> 
>, std::ios_base&, char, long) const 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296==    by 0x3C07E4CF: std::num_put<char, std::ostreambuf_iterator<char, 
std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, 
std::char_traits<char> >, std::ios_base&, char, long) const 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296== 
==296== Conditional jump or move depends on uninitialised value(s) 
==296==    at 0x3C07D9DD: std::__pad<char, std::char_traits<char> 
>::_S_pad(std::ios_base&, char, char*, char const*, int, int, bool) 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296==    by 0x3C07DA83: std::num_put<char, std::ostreambuf_iterator<char, 
std::char_traits<char> > >::_M_pad(char, int, std::ios_base&, char*, char 
const*, int&) const 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296==    by 0x3C07E94A: std::ostreambuf_iterator<char, std::char_traits<char> 
> std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > 
>::_M_convert_int<long>(std::ostreambuf_iterator<char, std::char_traits<char> 
>, std::ios_base&, char, long) const 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296==    by 0x3C07E4CF: std::num_put<char, std::ostreambuf_iterator<char, 
std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, 
std::char_traits<char> >, std::ios_base&, char, long) const 
(in /pkg/gcc.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.3/libstdc++.so.5.0.5) 
==296== 
==296== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 17 from 1) 
==296== malloc/free: in use at exit: 0 bytes in 0 blocks. 
==296== malloc/free: 2 allocs, 2 frees, 1138 bytes allocated. 
==296== For a detailed leak analysis,  rerun with: --leak-check=yes 
==296== For counts of detected errors, rerun with: -v 
andrew@bob andrew $

-- 
           Summary: stringstream/ostream/iomanip memory scribble bug
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: andrew at walrond dot org
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15645