Re: PR Fortran/91960 Patch

On Mon, Jan 12, 2026 at 09:48:56AM -0800, Jerry D wrote:
> On 1/11/26 12:33 PM, Steve Kargl wrote:
> > The attach patch fixes PR Fortran/91960.  This PR is another
> > one from Gerhard in 2019-10.01.  A patch has been lingering
> > in the PR since 2023-05-30.
> > 
> > The patch checks that an array constructor in a parameter
> > statement is in fact a constant expression.  I'll note
> > that the patch requires a special carve out to accommodate
> > the fix for Fortran/117070.
> > 
> > 2026-01-11  Steven G. Kargl  <[email protected]>
> > 
> > 	PR Fortran/91960
> > 	* resolve.cc (resolve_fl_parameter):  Check the righthand symbol
> > 	is a constant expression.
> > 
> > 2026-01-11  Steven G. Kargl  <[email protected]>
> > 
> > 	PR Fortran/91960
> > 	* gfortran.dg/pr69962.f90: Adjust testcase to ignore new error message.
> > 	* gfortran.dg/pr91960_1.f90: New test.
> > 	* gfortran.dg/pr91960_2.f90: Ditto.
> > 
> 
> I am wondering about the comment:
> 
> +      /* PR fortran/117070 argues a nonconstant proc pointer can appear in
> +	 the array constructor of a paramater.  I don't buy it, but... */
> +      if (sym->value->ts.type == BT_DERIVED
> +	  && sym->value->ts.u.derived
> +	  && sym->value->ts.u.derived->attr.proc_pointer_comp)
> +	return true;
> +      gfc_error ("Expecting constant expression near %L", &sym->value->where);
> +      return false;
> 
> It either is allowed or it is not. Do we need to review the Standard to
> confirm or deny this?
> 


It's probably easier to go see the audit in fortran/117070.
Here's a chopped down version of that PR.


  module funcs
   implicit none
   abstract interface
      function retchar()
         character(len=1) :: retchar
      end function
   end interface
   contains
      function a()
        character(len=1) :: a
        a = 'a'
      end function
  end module

  module dispatch_table
   use funcs
   implicit none
   private
   public :: table
   public :: build_table, pc

   ! Procedure container
   type :: pc
      procedure(retchar), pointer, nopass :: rc => null()
   end type

   ! Static dispatch table
   type(pc), parameter :: table(3) = [pc(a)]  ! Doesn't work
  end module

The fix for 117070 accepts the line marked '! Doesn't work'.
The argument in that PR is that pc(a) is a constant expression.
I don't see how the address of function can be considered a
constant expression; in particular, some OS's support address
relocation and randomization.

--  
Steve