[Bug fortran/33904] New: OpenMP: Default(shared) and wrong "lastprivate variable is private in outer context"

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

Reported by Vasileios Liaskovitis,
http://gcc.gnu.org/ml/fortran/2007-10/msg00339.html

The following valid program gives
"error: lastprivate variable "i2" is private in outer context"

------------------------------------
      SUBROUTINE foo(a, b, n)
      DOUBLE PRECISION a, b
      INTEGER*8 i1, i2, i3, n
      DIMENSION a(n,n,n), b(n,n,n)
!$OMP PARALLEL
!$OMP+DEFAULT(SHARED)
!$OMP+PRIVATE(I3)
!$OMP DO
!$OMP+LASTPRIVATE(I1,I2)
      DO i3 = 2, n-1, 1
       DO i2 = 2, n-1, 1
        DO i1 = 2, n-1, 1
         a(i1, i2, i3) = b(i1, i2, i3);
  600    CONTINUE
        ENDDO
       ENDDO
      ENDDO
!$OMP END DO NOWAIT
!$OMP END PARALLEL
      RETURN
      END
------------------------------------

Vasilis wrote:

I believe this code is compliant with the OPENMP 2.5 spec, since the
DEFAULT(SHARED) clause should make the scope of i1, i2 shared in the
enclosing parallel region. Pathscale 3.0, PGI 7.0.6 and Intel 10.0.026
compile the above code successfully.

Replacing:

!$OMP+DEFAULT(SHARED)
with:
!$OMP+SHARED(I1,I2)

makes the code compile successfully with gfortran. 
Alternatively, keeping DEFAULT(SHARED) and fusing the OMP PARALLEL
clause with the OMP DO clause (i.e. using OMP PARALLEL DO) also solves
the problem.

(this testcase is derived from a benchmark suite that doesn't allow
source code modifications. gfortran should be able to compile this with
no code changes - if this is indeed openmp-compliant code)

Could this behavior be due to the following libgomp patch not getting
all necessary information from the fortran front-end?

http://gcc.gnu.org/ml/gcc-patches/2007-01/msg01940.html


-- 
           Summary: OpenMP: Default(shared) and wrong "lastprivate variable
                    is private in outer context"
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: rejects-valid, openmp
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33904