[Bug fortran/41850] New: Wong-code with optional allocatable arrays

[burnus at gcc dot gnu dot org]

As reported by Thomas Robitaille at
http://gcc.gnu.org/ml/fortran/2009-10/msg00220.html
the following code gives wrong-code (segfault/buserror) at run time with GCC
4.2/4.3/4.4/4.5. (4.1 does not support allocatable dummies.)

$ ./a.out
 in sub1
Bus error


module test_module
  implicit none
contains
  subroutine sub2(a)
    implicit none
    real,allocatable,intent(out),optional :: a(:)
    print *,'in sub2'
  end subroutine sub2
  subroutine sub1(a)
    implicit none
    real,allocatable,intent(out),optional :: a(:)
    print *,'in sub1'
    call sub2(a)
  end subroutine sub1
end module test_module

program test
  use test_module
  implicit none
  call sub1()
end program


The problem is that the argument can be "NULL" - and there is no check for the
case "a == NULL"; i.e. the INTENT(OUT) autodeallocation block needs to be
enclosed with a "if (a !=NULL)" as remarked by Dennis
(http://gcc.gnu.org/ml/fortran/2009-10/msg00221.html).

sub1 (a)
{
  [...snip printing "in sub1" stuff...]
  {
    struct array1_real(kind=4) * D.555;
    if (a->data != 0B)
      {
        __builtin_free (a->data);
      }
    a->data = 0B;
    D.555 = a != 0B ? a : 0B;
    sub2 (D.555);
  }

By the way the line "D.555 = a != 0B ? a : 0B;" is redundant - and also not
nice because making the alias analysis for the middle end more difficult.


-- 
           Summary: Wong-code with optional allocatable arrays
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          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=41850