Re: [Patch, Fortran] PR 78392: ICE in gfc_trans_auto_array_allocation, at fortran/trans-array.c:5979

[Janus Weil <janus at gcc dot gnu dot org>]

Hi all,

> I previously assumed that the test case for this PR would be legal,
> but by now I think that's wrong. The test case should be rejected, and
> we already have checking mechanisms for this (see
> resolve_fl_variable), but apparently they are not working.
>
> My current suspicion is that 'gfc_is_constant_expr' has a bug, because
> it claims the call to the function 'get_i' to be a constant
> expression. This is not true, because get_i() can not be reduced to a
> compile-time constant.

some more reading in the standard confirms this suspicion: In
gfc_is_constant_expr there is a piece of code which claims that
specification functions are constant. That is certainly not true, and
so what I'm doing in the attached fix is to remove that code and add
some references to the standard to make things clearer.

The code that I'm removing has last been touched in this commit by
Jerry six years ago:

https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=166520

However, this did not introduce the bug in the first place (not sure
when that happened).

In any case the new patch in the attachment regtests cleanly and
correctly rejects the original test case as well as one of the cases
mentioned by Dominique. Ok for trunk?

Cheers,
Janus



2016-11-19  Janus Weil  <janus@gcc.gnu.org>

    PR fortran/78392
    * expr.c (gfc_is_constant_expr): Specification functions are not
    compile-time constants. Update documentation (add reference to F08
    standard), add a FIXME.
    (external_spec_function): Add reference to F08 standard.
    * resolve.c (resolve_fl_variable): Ditto.

2016-11-19  Janus Weil  <janus@gcc.gnu.org>

    PR fortran/78392
    * gfortran.dg/constant_shape.f90: New test case.

Attachment: pr78392_v3.diff
Description: Text document

! { dg-do compile }
!
! PR 78392: ICE in gfc_trans_auto_array_allocation, at fortran/trans-array.c:5979
!
! Contributed by Janus Weil <janus@gcc.gnu.org>

module mytypes
   implicit none
 contains
   pure integer function get_i ()
     get_i = 13
   end function
end module

program test
  use mytypes
  implicit none
  integer, dimension(get_i()) :: x  ! { dg-error "must have constant shape" }
  print *, size (x)
end