[Bug libstdc++/15015] New: Thread safety / race condition bug in iostreams on Solaris 5.9

[harri dot pasanen at trema dot com]

The following test program segfaults maybe 50% of the time on a SMP Solaris box, 
when compiled with gcc 3.2.3.  On Linux (Mandrake 9.1, default gcc 3.2.3) it seems to 
work fine. gcc 3.3.2 on HP-UX 11.00 also seemed to work. 
 
I went through the libstdc++-v3 ChangeLog, but I did not find any particular reference 
to this problem, or a fix. 
 
 
/***************************************************** 
 Test code to exercise iostreams under threads 
 
Compile with: 
   g++ -Wall -O2 thread-iostream.cxx -lpthread 
Execute: 
   ./a.out 
******************************************************/ 
#include <pthread.h> 
#include <iostream> 
#include <sstream> 
 
const int num_threads = 200; 
 
void *runner(void * param);   /* function that the thread will execute */ 
 
int main (int argc, const char **argv) 
{ 
  pthread_t tid[num_threads]; 
 
 for (int i = 0; i < num_threads; i ++) 
   pthread_create( &tid[i], NULL, runner, NULL); 
 
 for (int i = 0; i < num_threads; i ++) 
   pthread_join( tid[i], NULL);  // makes the main code wait for the thread  
 
 std::cout << "Exiting ok.\n"; 
 return 0; 
} 
 
void * runner(void *param) 
{ 
  std::stringstream fmt; 
   
  for (int i = 0; i < 10; i++) 
    fmt << "today" << 3.14157 << "is bogus\n"; 
 
  pthread_exit(0); 
  return 0; 
} 
// EOF for thread-iostream.cxx 
 
 
$ g++ -v 
Reading specs from /usr/gnu/lib/gcc-lib/sparc-sun-solaris2.9/3.2.3/specs 
Configured with: ../gcc-3.2.3/configure --prefix=/usr/gnu --with-gnu-as 
--with-cpu=supersparc --with-gnu-ld --enable-version-specific-runtime-libs 
--enable-long-long --enable-threads --enable-languages=c,c++ 
Thread model: posix 
gcc version 3.2.3 
 
 
The backtrace is: 
 
#0  std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > 
>::_M_widen_float(std::ostreambuf_iterator<char, std::char_traits<char> >, 
std::ios_base&, char, char*, int) const (this=0xff2f9838, __s= 
      {<iterator<std::output_iterator_tag,void,void,void,void>> = {<No data fields>}, 
_M_sbuf = 0xfe7fbea4, _M_failed = false}, __io=@0xfe7fbf0c, __fill=32 ' ', 
    __cs=0xfe7fbc20 "@\t!ïsÀÁý", __len=7) 
    at 
/raid5/BuildSwBuild/gcc-3.2.3-build/sparc-sun-solaris2.9/libstdc++-v3/include/bits/locale_facets.h:488 
4 
 
 
-Harri 
harri.pasanen at trema.com

-- 
           Summary: Thread safety / race condition bug in iostreams on
                    Solaris 5.9
           Product: gcc
           Version: 3.2.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: harri dot pasanen at trema dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15015