re PR fortran/80657 (Loop in character function declaration)

2018-05-19  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/80657
	* resolve.c (flag_fn_result_spec): Use the 'sym' argument to
	test for self refs to the function result in the character len
	expression. If a self reference is found, emit an error and
	return true.
	(resolve_fntype): Use the function symbol in the calls to the
	above.

2018-05-19  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/80657
	* gfortran.dg/char_result_18.f90: New test.

From-SVN: r260415

gcc/fortran/resolve.c

@@ -16217,7 +16217,7 @@ resolve_equivalence (gfc_equiv *eq)
 
 static bool
 flag_fn_result_spec (gfc_expr *expr,
-                     gfc_symbol *sym ATTRIBUTE_UNUSED,
+                     gfc_symbol *sym,
                      int *f ATTRIBUTE_UNUSED)
 {
   gfc_namespace *ns;
@@ -16230,6 +16230,13 @@ flag_fn_result_spec (gfc_expr *expr,
 	if (!ns->parent)
 	  break;
 
+      if (sym == s)
+	{
+	  gfc_error ("Self reference in character length expression "
+		     "for %qs at %L", sym->name, &expr->where);
+	  return true;
+	}
+
       if (!s->fn_result_spec
 	  && s->attr.flavor == FL_PARAMETER)
 	{
@@ -16312,7 +16319,7 @@ resolve_fntype (gfc_namespace *ns)
       }
 
   if (sym->ts.type == BT_CHARACTER)
-    gfc_traverse_expr (sym->ts.u.cl->length, NULL, flag_fn_result_spec, 0);
+    gfc_traverse_expr (sym->ts.u.cl->length, sym, flag_fn_result_spec, 0);
 }
 
 

gcc/testsuite/gfortran.dg/char_result_18.f90

+! { dg-do compile }
+!
+! Tests the fix for PR80657.
+!
+! Contributed by Vittorio Zecca  <zeccav@gmail.com>
+!
+function f(x)
+implicit character(len(f)) (x) ! { dg-error "Self reference in character length" }
+character(len(x)) f
+end