[Bug c++/32261] New: Thread race segfault in std::string::append with -O and -s

["appfault at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

Compiling with:
g++ -g -O3 gccbug.cpp -pthread -o gccbug -s

Note that removing the -s eliminates the segfault, as does removing
optimizations with -O0.

This occurs with gcc 3.3 and 3.3.6 but does not occur with the gcc 3.2.3
delivered as part of RedHat ES3.0u5.  It is also fixed in 3.4.6.

#include <pthread.h>
#include <string>

void* thread_function(void*) {
    for (int k = 0; k < 50000; k++) {
        std::string my_str;
        my_str += "foo";
    }
    return 0;
}

int main()
{
    pthread_t thread1, thread2;

    pthread_create(&thread1, NULL, thread_function, NULL);
    pthread_create(&thread2, NULL, thread_function, NULL);

    void* exitcode;
    pthread_join(thread1, &exitcode);
    pthread_join(thread2, &exitcode);

    return 0;
}

Example stack trace (as a courtesy to future googlers looking for this issue):
#0  0x00d3d4cc in memcpy () from /lib/libc.so.6
#1  0x00ba9120 in std::string::_Rep::_M_clone (this=0x804a700,
__alloc=@0x2012783, __res=28) at
/build_gnu_build/gcc-3.3.6/i386-redhat-linux/libstdc++-v3/include/bits/char_traits.h:155
#2  0x00ba7519 in std::string::reserve (this=0xb6bf43b0, __res=28) at
/build_gnu_build/gcc-3.3.6/i386-redhat-linux/libstdc++-v3/include/bits/basic_string.h:257
#3  0x00ba77be in std::string::append (this=0xb6bf43b0, __str=@0xb6bf43a0) at
/build_gnu_build/gcc-3.3.6/i386-redhat-linux/libstdc++-v3/include/bits/basic_string.tcc:680
#4  0x08048c21 in ?? ()
#5  0x080490da in ?? ()
#6  0x08049093 in ?? ()
#7  0x08048fa6 in ?? ()
#8  0x003ef9d9 in start_thread (arg=0xb6bf4bb0) at pthread_create.c:261
#9  0x00d86f0e in clone () from /lib/libc.so.6


-- 
           Summary: Thread race segfault in std::string::append with -O and
                    -s
           Product: gcc
           Version: 3.3.6
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: appfault at hotmail dot com
  GCC host triplet: 2.4.21-32.ELsmp #1 SMP Fri Apr 15 21:17:59 EDT 2005 i686
                    i686 i3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32261