[Bug fortran/88328] ICE in resolve_tag_format, at fortran/io.c:1641

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88328

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-12-03
     Ever confirmed|0                           |1

--- Comment #1 from kargl at gcc dot gnu.org ---
(In reply to G. Steinmetz from comment #0)
> Affects versions down to at least gcc-5 :
> 
> 
> $ cat z1.f90
> program p
>    character(3), parameter :: a(0) = [character(3)::]
>    print a
> end
> 
> 
> $ gfortran-9-20181202 -c z1.f90
> f951: internal compiler error: Segmentation fault
> 0xb2ec9f crash_signal
>         ../../gcc/toplev.c:326
> 0x63ddee resolve_tag_format
>         ../../gcc/fortran/io.c:1641

I get

% gfcx -c a.f90
a.f90:3:10:

    3 |    print a
      |          1
Error: FORMAT tag at (1) cannot be a zero-sized array

with this patch

Index: gcc/fortran/io.c
===================================================================
--- gcc/fortran/io.c    (revision 266710)
+++ gcc/fortran/io.c    (working copy)
@@ -1636,6 +1636,12 @@ resolve_tag_format (gfc_expr *e)
          gfc_expr *r;
          gfc_char_t *dest, *src;

+         if (e->value.constructor == NULL)
+           {
+             gfc_error ("FORMAT tag at %C cannot be a zero-sized array");
+             return false;
+           }
+
          n = 0;
          c = gfc_constructor_first (e->value.constructor);
          len = c->expr->value.character.length;
@@ -3231,12 +3237,17 @@ gfc_resolve_dt (gfc_dt *dt, locus *loc)
 {
   gfc_expr *e;
   io_kind k;
+  locus loc_tmp;

   /* This is set in any case.  */
   gcc_assert (dt->dt_io_kind);
   k = dt->dt_io_kind->value.iokind;

+  loc_tmp = gfc_current_locus;
+  gfc_current_locus = *loc;
   RESOLVE_TAG (&tag_format, dt->format_expr);
+  gfc_current_locus = loc_tmp;
+
   RESOLVE_TAG (&tag_rec, dt->rec);
   RESOLVE_TAG (&tag_spos, dt->pos);
   RESOLVE_TAG (&tag_advance, dt->advance);