Re: PR Fortran/91960 Patch

On 1/12/26 12:04 PM, Steve Kargl wrote:
> 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

I tested all of your test cases here with flang and it agrees with your error 
messages. Simalarly with you chopped down test case here. I also tested the 
proc_target_1.f90 with flang and it does not object. So at least one other 
compiler lines up with gfortran with your patch applied.


It does seem inconsistent so I want to revise the comment as:

       /* PR fortran/117070 argues a nonconstant proc pointer can appear in
	 the array constructor of a paramater.  This seems inconsistant with
	 the concept of a parameter. TODO: Needs an interpretation.  */

and plan to commit shortly.

Regards,

Jerry