[Bug libgomp/28468] New: OpenMP-parallelized program crashes when OMP_NUM_THREADS > 1

["bruno at clisp dot org" <gcc-bugzilla@gcc.gnu.org>]

Versions:
* gcc: gcc (GCC) 4.2.0 20060715 (experimental)
* cpu: AMD-K7 (i686)
* kernel: Linux 2.4.21-99 (SuSE 9.0)
* glibc: glibc-2.3.6 built with LinuxThreads, _not_ NPTL

Test program:
============================== omp-test1.c =======================
#include <stdlib.h>
#include <stdio.h>

/* A computational task whose duration depends on x.  */
int job (int x)
{
  int j = rand() % (100 + 10 * x);
  int i;

  for (i = j - 1; i > 0; i--)
    if (j % i == 0)
      break;

  return i;
}

int main (int argc, char *argv[])
{
  int n = 10000;

  int *mem = malloc (n * sizeof (int));
  int i;

  /* Because the tasks don't have all the same duration, a dynamic
     schedule is best.  */
  #pragma omp parallel for schedule(dynamic)
  for (i = 0; i < n; i++)
    mem[i] = job (i);

  for (i = 0; i < n; i++)
    printf ("mem[%d] = %d\n", i, mem[i]);

  return 0;
}
=====================================================================

$ gcc -fopenmp -Wall -O omp-test1.c

The single-threaded program runs fine:
$ unset OMP_NUM_THREADS; ./a.out
or
$ export OMP_NUM_THREADS=1; ./a.out

But with more than one thread it crashes:

$ export OMP_NUM_THREADS=2; ./a.out
Segmentation fault (core dumped)
$ gdb a.out core.26661
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This GDB was configured as "i686-pc-linux-gnu"...Using host libthread_db
library "/lib/libthread_db.so.1".

Core was generated by `./a.out'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from
/gfs/ibook/Volumes/ExtData/bin.x86-linux/gnu-inst-gcc/4.2-20060715/lib/gcc/i686-pc-linux-gnu/4.2.0/libgomp.so.1...done.
Loaded symbols for
/packages/gnu-inst-gcc/4.2-20060715/lib/gcc/i686-pc-linux-gnu/4.2.0/libgomp.so.1
Reading symbols from /lib/libpthread.so.0...done.
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/librt.so.1...done.
Loaded symbols for /lib/librt.so.1
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
#0  gomp_iter_dynamic_next (pstart=0xbfffe9c4, pend=0xbfffe9c8)
    at ../../../gcc-4.2-20060715/libgomp/iter.c:189
189       start = ws->next;
(gdb) where
#0  gomp_iter_dynamic_next (pstart=0xbfffe9c4, pend=0xbfffe9c8)
    at ../../../gcc-4.2-20060715/libgomp/iter.c:189
#1  0x4001c8e8 in gomp_loop_dynamic_next (istart=0xbfffe9c4, iend=0xbfffe9c8)
    at ../../../gcc-4.2-20060715/libgomp/loop.c:248
#2  0x080486ed in main.omp_fn.0 ()
#3  0x0804861e in main ()
(gdb) print ws
$1 = (struct gomp_work_share *) 0x0


-- 
           Summary: OpenMP-parallelized program crashes when OMP_NUM_THREADS
                    > 1
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgomp
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bruno at clisp dot org
 GCC build triplet: i686-suse-linux-gnu
  GCC host triplet: i686-suse-linux-gnu
GCC target triplet: i686-suse-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28468