[Bug fortran/95372] New: ICE in find_array_section, at fortran/expr.c:1687

[Bug fortran/95372] New: ICE in find_array_section, at fortran/expr.c:1687

[gscfq@t-online.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95372

            Bug ID: 95372
           Summary: ICE in find_array_section, at fortran/expr.c:1687
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gscfq@t-online.de
  Target Milestone: ---

Affects versions down to at least r5, works without parameter :


$ cat z1.f90
program p
   type t
      integer :: a = 1
   end type
   type(t), parameter :: x(3) = t()
   type(t) :: y(1)
   y = [x(2:2)]
   print *, y
end


$ cat z2.f90
program p
   type t
      integer :: a = 1
   end type
   type(t) :: x(3) = t()
   type(t) :: y(1)
   y = [x(2:2)]
   print *, y
end


$ gfortran-11-20200524 z2.f90 && ./a.out
           1
$
$ gfortran-11-20200524 -c z1.f90
f951: internal compiler error: in find_array_section, at fortran/expr.c:1687
0x655de5 find_array_section
        ../../gcc/fortran/expr.c:1687
0x65735a simplify_const_ref
        ../../gcc/fortran/expr.c:1892
0x657ebe gfc_simplify_expr(gfc_expr*, int)
        ../../gcc/fortran/expr.c:2278
0x6580c3 simplify_parameter_variable
        ../../gcc/fortran/expr.c:2107
0x657e8d gfc_simplify_expr(gfc_expr*, int)
        ../../gcc/fortran/expr.c:2245
0x6208fd expand_constructor
        ../../gcc/fortran/array.c:1814
0x622c77 gfc_array_size(gfc_expr*, __mpz_struct (*) [1])
        ../../gcc/fortran/array.c:2648
0x6bbfbf expression_shape
        ../../gcc/fortran/resolve.c:5390
0x6bbfbf gfc_expression_rank(gfc_expr*)
        ../../gcc/fortran/resolve.c:5464
0x6bd8bf gfc_resolve_expr(gfc_expr*)
        ../../gcc/fortran/resolve.c:7076
0x6c6144 gfc_resolve_expr(gfc_expr*)
        ../../gcc/fortran/resolve.c:11653
0x6c6144 gfc_resolve_code(gfc_code*, gfc_namespace*)
        ../../gcc/fortran/resolve.c:11746
0x6c7747 resolve_codes
        ../../gcc/fortran/resolve.c:17257
0x6c780e gfc_resolve(gfc_namespace*)
        ../../gcc/fortran/resolve.c:17292
0x6af99c resolve_all_program_units
        ../../gcc/fortran/parse.c:6245
0x6af99c gfc_parse_file()
        ../../gcc/fortran/parse.c:6492
0x6fb9af gfc_be_parse_file
        ../../gcc/fortran/f95-lang.c:210

[Bug fortran/95372] ICE in find_array_section, at fortran/expr.c:1687

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95372

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-06-05
                 CC|                            |kargl at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
           Priority|P3                          |P4

--- Comment #1 from kargl at gcc dot gnu.org ---
This allows the code to compile and print 1.

Index: gcc/fortran/expr.c
===================================================================
--- gcc/fortran/expr.c  (revision 280157)
+++ gcc/fortran/expr.c  (working copy)
@@ -1684,7 +1684,13 @@ find_array_section (gfc_expr *expr, gfc_ref *ref)
        }

       cons = gfc_constructor_lookup (base, limit);
-      gcc_assert (cons);
+
+      if (!cons)
+       {
+         t = false;
+         goto cleanup;
+       }
+
       gfc_constructor_append_expr (&expr->value.constructor,
                                   gfc_copy_expr (cons->expr), NULL);
     }

[Bug fortran/95372] ICE in find_array_section, at fortran/expr.c:1687

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95372

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |anlauf at gcc dot gnu.org
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |anlauf at gcc dot gnu.org

--- Comment #2 from anlauf at gcc dot gnu.org ---
Patch: https://gcc.gnu.org/pipermail/fortran/2020-December/055420.html

[Bug fortran/95372] ICE in find_array_section, at fortran/expr.c:1687

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95372

--- Comment #3 from anlauf at gcc dot gnu.org ---
Playing around with the above patches, I found that the following now gets
rejected instead of an ICE:

program p
  type t
     integer :: a = 1
  end type t
  type(t), parameter :: z(3) = t()
  type(t)            :: v(1) =  z(2:2)  ! Rejected
! type(t)            :: v(1) = [z(2:2)] ! Rejected
  print *, v% a
end

pr95372-1.f90:6:3:

    6 |   type(t)            :: v(1) =  z(2:2)  ! Rejected
      |   1
Error: Unclassifiable statement at (1)
pr95372-1.f90:8:14:

    8 |   print *, v% a
      |              1
Error: Symbol 'v' at (1) has no IMPLICIT type


This is a consequence of find_array_section returning false instead of true.
However, removing the t=false from the patch the original testcase will ICE
in a different place.

Staring some more at the code in find_array_section, it appears that there
is a stale

  cons = gfc_constructor_first (base);

followed later by the critical

      cons = gfc_constructor_lookup (base, limit);

Strange.  And "git blame" so far did not really help me much.

[Bug fortran/95372] ICE in find_array_section, at fortran/expr.c:1687

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95372

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |WAITING

--- Comment #4 from anlauf at gcc dot gnu.org ---
Seems to work at r12-6697, r11-9477 and r10-10403.  gcc-9 still fails.

Does a bisection make sense to find what fixed it?

Otherwise we could close it and set the target milestone to 10.4.

[Bug fortran/95372] ICE in find_array_section, at fortran/expr.c:1687

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95372

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|WAITING                     |RESOLVED
   Target Milestone|---                         |10.5

--- Comment #5 from anlauf at gcc dot gnu.org ---
Fixed in gcc-10+, thus closing.