Re: [Patch, Fortran] F2008: Null pointer/non-allocated as absent dummy

[Daniel Kraft <d at domob dot eu>]

Tobias Burnus wrote:
>  And yet another rather trivial F2008 change... (hours later) ... well, 
> maybe it is not as trivial as I thought, but here it is.
>
> The rules for absent actual arguments to optional dummies was changed 
> from Fortran 2003 (12.4.1.6 Restrictions on dummy arguments not present) 
> to Fortran 2008 (12.5.2.12 Argument presence and restrictions on 
> arguments not present) by adding the following:
>
> A dummy argument [...] is not present if the dummy argument [...]
> does not have the ALLOCATABLE or POINTER attribute, and corresponds to 
> an actual argument that
> * has the ALLOCATABLE attribute and is not allocated, or
> * has the POINTER attribute and is disassociated."
>
> That mostly matches the current "present()" checks, except for 
> descriptors (where the data element is NULL) and for directly passing 
> EXPR_NULL. (At least I read it such that passing NULL() is allowed.) 
> Thus, removing some checks - and changes for EXPR_NULL and assumed-shape 
> arrays was all what was needed.
>
> I also added a check that NULL() is not used for allocatable or 
> non-optional dummies.
>
> Build and regtested on x86-64-linux. OK for the trunk?

Yes.

I just don't really like the way

+      if (a->expr->expr_type == EXPR_NULL && !f->sym->attr.pointer
+	  && (f->sym->attr.allocatable || !f->sym->attr.optional
+	      || (gfc_option.allow_std & GFC_STD_F2008) == 0))
+	{
+	  if (where && (f->sym->attr.allocatable || !f->sym->attr.optional))
+	    gfc_error ("Unexpected NULL() intrinsic at %L to dummy '%s'",
+		       where, f->sym->name);
+	  else if (where)
+	    gfc_error ("Fortran 2008: Null pointer at %L to non-pointer "
+		       "dummy '%s'", where, f->sym->name);
+
+	  return 0;
+	}

is formulated; I'd probably do

if(where)
  {
     if(...)
     else
  }

instead of the if-elseif construct; and maybe the F2008 check first and 
the (ALLOCATABLE || !OPTIONAL) as else as this is a more complicated 
expression?

Just my personal taste, though.

Thanks for your patches,
Daniel

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