[Bug fortran/40876] New: OpenMP private variable referenced in a statement function

[Bug fortran/40876] New: OpenMP private variable referenced in a statement function

[longb at cray dot com]

Beginning with the OpenMP API Version 2.5, this case should fail at
compile-time.  The gfortran compiler does not reject this case, but gets a
segmentation fault at run-time.

The OpenMP API Version 3.0 (May 2008) lists the following restriction to a
private clause on p 91. lines 29-30:

" * Variables that appear in ... expressions for statement function
definitions, may not appear in a private clause."

Test case:

> cat ISU3136.f90
! derived from OpenMP test omp1/F2_6_2_1_2a.f90
!     According to OpenMP API Ver 2.5 May 2005 p. 75 lines 19/20
!     this is a negative test that should fail at compile-time.
      use omp_lib
      implicit none
      integer, parameter :: NT = 4
      integer :: nThreads(NT)
      integer :: a, st_func, i
      st_func() = a + 1

!$    call omp_set_dynamic(.false.)
!$    call omp_set_num_threads(NT)

!$omp parallel private(a)
      a = omp_get_thread_num()
!$omp barrier
      nThreads(omp_get_thread_num()+1) = st_func()
!$omp end parallel

      do i = 1, NT
          if(nThreads(i) /= i) then
              print*, 'FAIL: non-private copy is used in a statement function.'
          endif
      enddo

      END

> ftn -o x -fopenmp ISU3136.f90
> aprun -n 1 ./x
Application 1190869 exit signals: Segmentation fault
Application 1190869 resources: utime 0, stime 0

Expected output (using the Cray compiler) with a compile-time message:

> module swap PrgEnv-gnu PrgEnv-cray
> ftn -o x -h omp ISU3136.f90

!$omp parallel private(a)
                       ^  
ftn-1760 crayftn: ERROR $MAIN, File = ISU3136.f90, Line = 14, Column = 24 
  "A" is referenced in a statement function expression, so it must not be
specified in the PRIVATE, FIRSTPRIVATE or LASTPRIVATE clause.


-- 
           Summary: OpenMP private variable referenced in a statement
                    function
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: longb at cray dot com
 GCC build triplet: x86_64-suse-linux
  GCC host triplet: x86_64-suse-linux
GCC target triplet: x86_64-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[jakub at gcc dot gnu dot org]

-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
           Keywords|                            |openmp
   Last reconfirmed|0000-00-00 00:00:00         |2009-07-27 22:47:35
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[jakub at gcc dot gnu dot org]

------- Comment #1 from jakub at gcc dot gnu dot org  2009-07-28 12:20 -------
I certainly can't reproduce any kind of segfault with this.
And, it is unclear to me whether this restriction (why it is there at all,
doesn't make much sense) is meant just for statement functions referenced
within the omp region, or any.  Say is:
integer :: a, st_func
st_func () = a
!$omp parallel private (a)
a = 1
!$omp end parallel
end
also supposed to be invalid?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[longb at cray dot com]

------- Comment #2 from longb at cray dot com  2009-07-28 13:47 -------
The text at [75:19-20] of the OpenMP 2.5 standard, May 2008, says:

"Variables that appear in namelist statements, in variable format expressions,
and in Fortran expressions for statement function definitions, may not appear
in a private clause."

So the example in Comment #1 looks invalid.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[jv244 at cam dot ac dot uk]

------- Comment #3 from jv244 at cam dot ac dot uk  2009-07-28 14:34 -------
(In reply to comment #1)
> I certainly can't reproduce any kind of segfault with this.

It could be that it segfaults for Bill because 'ftn' adds -static to the
compiler options, but doesn't link libpthread with '-Wl,--whole-archive
-lpthread -Wl,--no-whole-archive' (see PR39176). Certainly, this happened in
the past on the XT5. It is something Bill could check on the Cray :-)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[burnus at gcc dot gnu dot org]

------- Comment #4 from burnus at gcc dot gnu dot org  2009-07-28 14:43 -------
(In reply to comment #1)
> I certainly can't reproduce any kind of segfault with this.

Neither can I.  Regarding both examples (comment 0 and comment 1), ifort 11.1
happily accepts both.

I am not sure whether it is the correct interpretation according the standard,
but
http://publib.boulder.ibm.com/infocenter/lnxpcomp/v9v111/topic/com.ibm.xlf111.linux.doc/xlfopg/smpdirclauses.htm
has:


"The following example demonstrates the proper use of a PRIVATE variable that
is used to define a statement function. A commented line shows the invalid use.
Since J appears in a statement function, the statement function cannot be
referenced within the parallel construct for which J is PRIVATE.

      INTEGER :: ARR(10), J = 17
      ISTFNC() = J

!$OMP PARALLEL DO PRIVATE(J)
      DO I = 1, 10
         J=I
         ARR(I) = J
      !  ARR(I) = ISTFNC() **ERROR**   A reference to ISTFNC would
                                       ! make the PRIVATE(J) clause
                                       ! invalid.
      END DO
      PRINT *, ARR
      END
"

However, I somehow read the standard differently such that already the
"PRIVATE(J)" is invalid.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[longb at cray dot com]

------- Comment #5 from longb at cray dot com  2009-11-13 22:19 -------
I tried 4.4.2 and do not any longer see the segfault on the Cray XT system.  I
suspect this was fixed by addressing the problem noted in Comment #3. 

The original problem of not issuing the error message at compile time remains.
This (correct) comment in Comment #5:

---
However, I somehow read the standard differently such that already the
"PRIVATE(J)" is invalid.
---

focuses on the actual issue.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[dfranke at gcc dot gnu dot org]

------- Comment #6 from dfranke at gcc dot gnu dot org  2010-05-07 19:50 -------
(In reply to comment #5)
> I tried 4.4.2 and do not any longer see the segfault on the Cray XT system.

This PR can thus be closed?


-- 

dfranke at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[longb at cray dot com]

------- Comment #7 from longb at cray dot com  2010-05-07 22:06 -------
The original problem reported in the Description concerned a missing error
message.  So, fixing the segfault (while an excellent situation) does not
address the original issue.  My 2 cents is this is not ready to close yet.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[longb at cray dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

Bill Long <longb at cray dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|DUPLICATE                   |---
             Status|RESOLVED                    |REOPENED

--- Comment #11 from Bill Long <longb at cray dot com> ---
With 10.2.0 there is still no error message for the invalid use of A in a
private() clause of the OpenMP directive.

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[longb at cray dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

--- Comment #8 from Bill Long <longb at cray dot com> 2010-12-27 01:42:20 UTC ---
I am out of the office until Monday, January 3, 2011.  Send technical questions
to spslang@cray.com.

[Bug fortran/40876] OpenMP private variable referenced in a statement function

[dfranke at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40876

Daniel Franke <dfranke at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
                 CC|                            |dfranke at gcc dot gnu.org