[Bug libfortran/48958] New: Add runtime diagnostics for SIZE intrinsic function

[Bug libfortran/48958] New: Add runtime diagnostics for SIZE intrinsic function

[thenlich at users dot sourceforge.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48958

           Summary: Add runtime diagnostics for SIZE intrinsic function
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: thenlich@users.sourceforge.net


As has been brought up before (Bug 20406), the SIZE intrinsic returns an
unpredictable result if the argument is an unallocated allocatable or a pointer
that is not associated.

While this is perfectly standard-conforming behaviour, it would be helpful in
program development to have SIZE throw a runtime error if this condition
occurs.

I.e. SIZE should first check if an array is ALLOCATED or a pointer is
ASSOCIATED and abort with a runtime error if that is not the case.

Fortran 2008:

13.7.156 SIZE (ARRAY [, DIM, KIND])
3 Arguments.
ARRAY shall be an array of any type. It shall not be an unallocated allocatable
variable or a pointer that is not associated. If ARRAY is an assumed-size
array, DIM shall be present with a value less than the rank of ARRAY.

[Bug libfortran/48958] Add runtime diagnostics for SIZE intrinsic function

[anlauf at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48958

Harald Anlauf <anlauf at gmx dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |anlauf at gmx dot de

--- Comment #2 from Harald Anlauf <anlauf at gmx dot de> ---
There are a few inquiry functions (SIZE, SHAPE, (L,U)BOUND) where such
a diagnostic might be useful.  It could be hidden behind one of the
-fcheck options.

However:

Depending on the implementation, it might work only for ALLOCATABLE,
where there is no undefined allocation status.  For a POINTER, the
status could be undefined, and it is not possible to discover this.
(It is even nice to be able to find out what the last size was
before deallocating the target of the pointer...)

NAG does the following:

% cat pr48958.f90
!integer, allocatable :: a(:)
integer, pointer :: a(:)
print *, size (a)
end
% nagfor -C pr48958.f90 && ./a.out 
NAG Fortran Compiler Release 5.3.1(907)
[NAG Fortran Compiler normal termination]
Runtime Error: pr48958.f90, line 3: Reference to undefined POINTER A
Program terminated by fatal error
Abort

Not sure whether there are other compilers which can handle this.

[Bug libfortran/48958] Add runtime diagnostics for SIZE intrinsic function

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48958

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
This PR is related to pr46182. While I agree that it would be nice to have run
time errors for invalid use of unallocated variables/not associated pointers, I
doubt it will ever happen.

[Bug libfortran/48958] Add runtime diagnostics for SIZE intrinsic function

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48958

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |anlauf at gcc dot gnu.org

--- Comment #5 from anlauf at gcc dot gnu.org ---
Incomplete patch:
https://gcc.gnu.org/pipermail/fortran/2020-November/055300.html

[Bug libfortran/48958] Add runtime diagnostics for SIZE intrinsic function

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48958

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Harald Anlauf <anlauf@gcc.gnu.org>:

https://gcc.gnu.org/g:0c81ccc3d87098b93b0e6a2dd76815e4d6e78ff0

commit r11-5064-g0c81ccc3d87098b93b0e6a2dd76815e4d6e78ff0
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Mon Nov 16 22:00:58 2020 +0100

    PR fortran/48958 - Add runtime diagnostics for SIZE intrinsic function

    Add code for runtime checking of status of ALLOCATABLE and POINTER
    arguments to the SIZE intrinsic when -fcheck=pointer is specified.

    gcc/fortran/ChangeLog:

            * trans-intrinsic.c (gfc_conv_intrinsic_size): Generate runtime
            checking code for status of argument.

    gcc/testsuite/ChangeLog:

            * gfortran.dg/pr48958.f90: New test.

[Bug fortran/48958] Add runtime diagnostics for SIZE intrinsic function

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48958

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P5
             Status|SUSPENDED                   |NEW
                 CC|anlauf at gmx dot de               |
          Component|libfortran                  |fortran

--- Comment #7 from anlauf at gcc dot gnu.org ---
The question on what to do with runtime checks and possibly undefined pointers,
which has been repeated by Thomas on the ML, could be solved by initializing
the data component when -fcheck=pointer is specified.

A somewhat hackish solution which regtests cleanly:

diff --git a/gcc/fortran/trans-array.c b/gcc/fortran/trans-array.c
index b2c39aa32de..6e1f27ead45 100644
--- a/gcc/fortran/trans-array.c
+++ b/gcc/fortran/trans-array.c
@@ -10668,7 +10668,9 @@ gfc_trans_deferred_array (gfc_symbol * sym,
gfc_wrapped_block * block)
     }

   /* NULLIFY the data pointer, for non-saved allocatables.  */
-  if (GFC_DESCRIPTOR_TYPE_P (type) && !sym->attr.save &&
sym->attr.allocatable)
+  if (GFC_DESCRIPTOR_TYPE_P (type) && !sym->attr.save
+      && (sym->attr.allocatable
+         || (sym->attr.pointer && (gfc_option.rtcheck &
GFC_RTCHECK_POINTER))))
     {
       gfc_conv_descriptor_data_set (&init, descriptor, null_pointer_node);
       if (flag_coarray == GFC_FCOARRAY_LIB && sym->attr.codimension)

Still need to learn weather this is the right solution, but it does the job.