re PR fortran/87782 (runtime error: load of value 1818451807, which is not a…

re PR fortran/87782 (runtime error: load of value 1818451807, which is not a valid value for type 'expr_t')

2018-11-01  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/87782
	* frontend-passes.c (constant_string_length): If there is a
	substring with a length which cannot be reduced to a constant,
	return NULL.

From-SVN: r265730

gcc/fortran/ChangeLog

+2018-11-01  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/87782
+	* frontend-passes.c (constant_string_length): If there is a
+	substring with a length which cannot be reduced to a constant,
+	return NULL.
+
 2018-11-01  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/40196

gcc/fortran/frontend-passes.c

@@ -638,23 +638,27 @@ constant_string_length (gfc_expr *e)
 	return gfc_copy_expr(length);
     }
 
-  /* Return length of substring, if constant. */
+  /* See if there is a substring. If it has a constant length, return
+     that and NULL otherwise.  */
   for (ref = e->ref; ref; ref = ref->next)
     {
-      if (ref->type == REF_SUBSTRING
-	  && gfc_dep_difference (ref->u.ss.end, ref->u.ss.start, &value))
+      if (ref->type == REF_SUBSTRING)
 	{
-	  res = gfc_get_constant_expr (BT_INTEGER, gfc_charlen_int_kind,
-				       &e->where);
+	  if (gfc_dep_difference (ref->u.ss.end, ref->u.ss.start, &value))
+	    {
+	      res = gfc_get_constant_expr (BT_INTEGER, gfc_charlen_int_kind,
+					   &e->where);
 
-	  mpz_add_ui (res->value.integer, value, 1);
-	  mpz_clear (value);
-	  return res;
+	      mpz_add_ui (res->value.integer, value, 1);
+	      mpz_clear (value);
+	      return res;
+	    }
+	  else
+	    return NULL;
 	}
     }
 
   /* Return length of char symbol, if constant.  */
-
   if (e->symtree && e->symtree->n.sym->ts.u.cl
       && e->symtree->n.sym->ts.u.cl->length
       && e->symtree->n.sym->ts.u.cl->length->expr_type == EXPR_CONSTANT)