Segmentation fault at runtime with OpenMP

[Tobias Burnus]

Ignacio Fernández Galván wrote:
> Is there anything wrong with this code? It compiles fine with
> gfortran-20080206, but when I run the output I get a segmentation
> fault.
>   
Using gfortran it does not crash here, but valgrind shows:

==10362== Use of uninitialised value of size 8
==10362==    at 0x400926: inner.902 (aa.f90:15)
==10362==    by 0x4008FA: MAIN__.omp_fn.0 (aa.f90:8)
==10362==    by 0x400875: MAIN__ (aa.f90:8)
==10362==    by 0x40095B: main (fmain.c:21)


The problem seems to be the variable k, which is uninitialized in the 
subroutine "inner". Jakub, is the code valid or not?


PROGRAM Outer
  IMPLICIT NONE
  REAL, DIMENSION(100) :: A
  INTEGER :: k

!$OMP PARALLEL DO PRIVATE(k)
  DO k=1,SIZE(A)
    CALL Inner()
  END DO
!$OMP END PARALLEL DO

  CONTAINS
  SUBROUTINE Inner
    IMPLICIT NONE
    A(k)=0.0D0
  END SUBROUTINE Inner

END PROGRAM Outer



The 010t.omplower tree looks as follows:

;; Function inner (inner.902)

inner ()
{
  integer(kind=4) k [value-expr: CHAIN.2->k];
  real(kind=4) a[100] [value-expr: CHAIN.2->a];
  integer(kind=4) D.915;
  integer(kind=8) D.909;
  integer(kind=8) D.910;

  D.915 = CHAIN.2->k;
  D.909 = (integer(kind=8)) D.915;
  D.910 = D.909 + -1;
  CHAIN.2->a[D.910] = 0.0;
}



;; Function outer (MAIN__)

outer ()
{
  struct .omp_data_s.3 .omp_data_o.4;
  struct FRAME.outer * D.927;

  _gfortran_set_options (7, &options.0);
  {
    .omp_data_o.4.FRAME.1 = &FRAME.1;
    #pragma omp parallel shared(FRAME.1) private(k) [child fn: MAIN__.omp_fn.0 (.omp_data_o.4)]
      {
        .omp_data_i = &.omp_data_o.4;
        {
          #pragma omp for nowait
          for (k = 1; k <= 100; k = k + 1)
          {
            D.927 = .omp_data_i->FRAME.1;
            inner () [static-chain: D.927];
          }
          <D.926>:;
          OMP_CONTINUE <k <- k>
          OMP_RETURN [nowait]
        }
        OMP_RETURN
      }
  }
}