[Bug fortran/78021] [5/6/7 Regression] Wrong result with optimization on character constant

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78021

--- Comment #3 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
This looks promising, modulo some line breaks:

Index: dependency.c
===================================================================
--- dependency.c        (Revision 240928)
+++ dependency.c        (Arbeitskopie)
@@ -226,10 +226,24 @@ gfc_dep_compare_functions (gfc_expr *e1, gfc_expr
          if ((args1->expr == NULL) ^ (args2->expr == NULL))
            return -2;

-         if (args1->expr != NULL && args2->expr != NULL
-             && gfc_dep_compare_expr (args1->expr, args2->expr) != 0)
-           return -2;
+         if (args1->expr != NULL && args2->expr != NULL)
+           {
+             gfc_expr *e1, *e2;
+             e1 = args1->expr;
+             e2 = args2->expr;

+             if (gfc_dep_compare_expr (e1, e2) != 0)
+               return -2;
+
+             /* Special case: String arguments which compare equal can
+                still have different lengths, which makes them different
calls.   */
+             
+             if (e1->expr_type == EXPR_CONSTANT && e1->ts.type == BT_CHARACTER
+                 && e2->expr_type == EXPR_CONSTANT && e2->ts.type ==
BT_CHARACTER
+                 && e1->value.character.length != e2->value.character.length)
+               return -2;
+           }
+
          args1 = args1->next;
          args2 = args2->next;
        }