On Thu, Jan 28, 2021 at 10:04:12AM -0500, Jason Merrill wrote:
> > We emit a bogus warning on the following testcase, suggesting that the
> > operator should return *this even when it does that already.
> > The problem is that normally cp_build_indirect_ref_1 ensures that *this
> > is folded as current_class_ref, but in templates (if return type is
> > non-dependent, otherwise check_return_expr doesn't check it) it didn't
> > go through cp_build_indirect_ref_1, but just built another INDIRECT_REF.
>
> That seems like a bug in build_x_indirect_ref.
So do you want this instead (if it passes bootstrap/regtest)?
2021-01-28 Jakub Jelinek <ja...@redhat.com>
PR c++/98841
* typeck.c (build_x_indirect_ref): For *this, return current_class_ref.
* g++.dg/warn/effc5.C: New test.
--- gcc/cp/typeck.c.jj 2021-01-27 11:48:49.715890458 +0100
+++ gcc/cp/typeck.c 2021-01-28 16:17:18.712755173 +0100
@@ -3326,7 +3326,15 @@ build_x_indirect_ref (location_t loc, tr
{
/* Retain the type if we know the operand is a pointer. */
if (TREE_TYPE (expr) && INDIRECT_TYPE_P (TREE_TYPE (expr)))
- return build_min (INDIRECT_REF, TREE_TYPE (TREE_TYPE (expr)), expr);
+ {
+ if (expr == current_class_ptr
+ || (TREE_CODE (expr) == NOP_EXPR
+ && TREE_OPERAND (expr, 0) == current_class_ptr
+ && (same_type_ignoring_top_level_qualifiers_p
+ (TREE_TYPE (expr), TREE_TYPE (current_class_ptr)))))
+ return current_class_ref;
+ return build_min (INDIRECT_REF, TREE_TYPE (TREE_TYPE (expr)), expr);
+ }
if (type_dependent_expression_p (expr))
return build_min_nt_loc (loc, INDIRECT_REF, expr);
expr = build_non_dependent_expr (expr);
--- gcc/testsuite/g++.dg/warn/effc5.C.jj 2021-01-28 16:15:05.820256255
+0100
+++ gcc/testsuite/g++.dg/warn/effc5.C 2021-01-28 16:15:05.820256255 +0100
@@ -0,0 +1,17 @@
+// PR c++/98841
+// { dg-do compile }
+// { dg-options "-Weffc++" }
+
+struct S {
+ template <typename T>
+ S& operator=(const T&) { return *this; } // { dg-bogus "should return a
reference to" }
+ S& operator=(const S&) { return *this; }
+};
+
+void
+foo ()
+{
+ S s, t;
+ s = 1;
+ s = t;
+}
Jakub
