[Bug fortran/34547] New: NULL(): Fortran 2003 changes, accepts invalid, ICE on invalid

["burnus at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The following gives an ICE:

  print *, NULL()

The program is invalid as the MOLD of NULL([MOLD]) is required in this context
(see F2003, 13.7.88): "If MOLD is absent, the characteristics of the result are
determined by the entity with which the reference is associated. See Table
13.1. MOLD shall not be absent in any other context."

Table 13.1 contains: rhs of pointer assignment; initialization of an object in
a declaration; default component init; struct constr; actual argument; in a
DATA statement.

Likewise for Fortran 97, see 7.1.4.1 around Table 7.2 - and 13.14.79.

---------------------

 integer, allocatable :: i(:)
 print *, NULL(i)

Prints: Error: 'mold' argument of 'null' intrinsic at (1) must be a POINTER.

While Fortran 97 has: "MOLD shall be a pointer and may be of any type."
Fortran 2003 has: "MOLD shall be a pointer or allocatable. It may be of any
type or may be a procedure pointer".

----

NULL as actual argument:

  external foo
  call foo(NULL())

is invalid without a MOLD as (F2003, similar in F97):
"If any type parameters of the contextual entity are deferred, those type
parameters of the result are deferred. If any type parameters of the contextual
entity are assumed, MOLD shall be present.
If the context of the reference to NULL is an actual argument to a generic
procedure, MOLD shall be present if the type, type parameters, or rank is
required to resolve the generic reference. MOLD shall also be present if the
reference appears as an actual argument corresponding to a dummy argument with
assumed character length."

---

Someone could also check whether we do the right thing for:
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/5a1e0cc2c7eb95cc/


-- 
           Summary: NULL(): Fortran 2003 changes, accepts invalid, ICE on
                    invalid
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-code, rejects-valid, accepts-invalid,
                    diagnostic
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34547