[Patch, Fortran] PR 35831: checking for dummy procedures

[Tobias Burnus]

On 08/05/2012 11:12 PM, Janus Weil wrote:
> here is a patch for a rather old PR, which deals with correctness
> checking for several cases, such as:
> 1) dummy procedures
> 2) proc-ptr assignments
> 3) type-bound procedure overloading
>
> The patch adds a new function 'check_result_characteristics' to do
> various checks on function results. This is largely analogous to
> 'check_dummy_characteristics'. In both of them, there are still a few
> attributes left to check, which I may add in a follow-up patch. Also I
> had to disable the warning for cases where we can not finally
> determine whether the string length or shape expressions are equal.
> The treatment for those cases should be improved at some point, or one
> should think about re-enabling the warnings.
>
> Regtested on x86_64-unknown-linux-gnu. Ok for trunk?

Thanks for the patch. However, I wonder about:

+  /* Check ALLOCATABLE attribute.  */
+  if (r1->attr.allocatable != r2->attr.allocatable)
+    {
+      snprintf (errmsg, err_len, "ALLOCATABLE mismatch in function result");
+      return FAILURE;
+    }

Shouldn't one check whether errmsg != NULL? That should only occur with 
generic resolution, but my impression is that that code is reached.

Additionally, I find "ALLOCATABLE mismatch" a bit unclear and would 
prefer something like "ALLOCATABLE attribute mismatch".

(Ditto for some other cases.)

Other items to check for: CONTIGUOUS, type-length parameter (string 
length), procedure-pointer results. For strings, one can have deferred 
("len=:", ts.deferred) and explicit size (len=n, len=3 etc.). I think 
you should at least add CONTIGUOUS as it is simple - and mention the 
string length in the FIXME.

With those changes, I am fine with the patch.

Tobias

PS: Some remarks, triggered by your patch but only remotely related. 
Though, I wouldn't mind if you (or someone else) could work on one of 
those ;-)

Side remark 1: Talking about generic resolution: I think we should at 
some point implement diagnostic for generic calls as well. If the 
interface matches (according to ambiguity rules), it makes sense to also 
print an error if there is a mismatch. Currently, gfortran just prints 
that no specific proc to the a generic name has been found, which 
requires extensive digging until one find the "correct" specific 
function and sees that, e.g., the dummy procedure has an argument with 
intent(inout) and the one of the acutal
argument has no intent specified. [PR40276.]

Side remark 1a: F2008 has relaxed some ambiguity rules; at some point we 
have to implement them. (PR 45521)

Side remark 2: I think we should split the type-rank mismatch diagnostic 
and print the gfc_typename() and, respectively, rank in the error 
message; one probably should pass on the errmsg as one also needs to 
check the kind and not only the type.

(I recently run into the issues of side remark 1 and 2: First the 
no-specific-proc-found error; then, calling the specific function, the 
type/rank error; it took us a while to see that the type was okay about 
not the rank.)

Side remark 3: I probably introduced a bug with my recent 
assumed-type/assumed-rank patches: It regards assumed-type/assumed-rank 
compatible to any other type/rank. That makes sense for checking dummy 
arguments - but not to check the interface of dummy procedures. For 
assumed-rank, an as->type check might catch it (untested), but I fear 
that type(*) is mishandled.

Side remark 4: The following program ICEs in check_assumed_size_reference's
1386      if ((e->ref->u.ar.end[e->ref->u.ar.as->rank - 1] == NULL)
as e->ref == NULL.

implicit none
contains
function g()
   integer :: g(*)
end function g

subroutine test()
   procedure(g), pointer :: x
   x => g
end subroutine test
end

> 2012-08-05  Janus Weil  <janus@gcc.gnu.org>
>
> 	PR fortran/35831
> 	* interface.c (check_result_characteristics): New function, which checks
> 	the characteristics of function results.
> 	(gfc_compare_interfaces,gfc_check_typebound_override): Call it.
>
> 2012-08-05  Janus Weil  <janus@gcc.gnu.org>
>
> 	PR fortran/35831
> 	* gfortran.dg/dummy_procedure_5.f90: Modified.
> 	* gfortran.dg/dummy_procedure_8.f90: New.
> 	* gfortran.dg/interface_26.f90: Modified.
> 	* gfortran.dg/proc_ptr_11.f90: Modified.
> 	* gfortran.dg/proc_ptr_15.f90: Modified.
> 	* gfortran.dg/proc_ptr_result_5.f90: Modified.
> 	* gfortran.dg/typebound_override_1.f90: Modified.
> 	* gfortran.dg/typebound_proc_6.f03: Modified.