Hi!
The comment in OBJ_TYPE_REF handling code correctly says that we are
looking for x.D.2103.D.2094, but it is important that x is not an
INDIRECT_REF or something similar as in the following testcase - we can't
really devirtualize in that case because we really don't know what it points
to. The following patch ensures that the argument got evaluated to address
of some field of (ultimately) a decl, which is all we should get during
valid constexpr evaluation.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-11-20 Jakub Jelinek <ja...@redhat.com>
PR c++/88110
* constexpr.c (cxx_eval_constant_expression) <case OBJ_TYPE_REF>: Punt
if get_base_address of ADDR_EXPR operand is not a DECL_P.
* g++.dg/cpp2a/constexpr-virtual13.C: New test.
--- gcc/cp/constexpr.c.jj 2018-11-19 14:24:49.000000000 +0100
+++ gcc/cp/constexpr.c 2018-11-20 15:03:26.968152935 +0100
@@ -4815,7 +4815,8 @@ cxx_eval_constant_expression (const cons
obj = cxx_eval_constant_expression (ctx, obj, lval, non_constant_p,
overflow_p);
/* We expect something in the form of &x.D.2103.D.2094; get x. */
- if (TREE_CODE (obj) != ADDR_EXPR)
+ if (TREE_CODE (obj) != ADDR_EXPR
+ || !DECL_P (get_base_address (TREE_OPERAND (obj, 0))))
{
if (!ctx->quiet)
error_at (cp_expr_loc_or_loc (t, input_location),
--- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual13.C.jj 2018-11-20
15:07:17.558386765 +0100
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-virtual13.C 2018-11-20
15:05:30.188140420 +0100
@@ -0,0 +1,20 @@
+// PR c++/88110
+// { dg-do compile }
+
+struct A {
+ virtual int foo () const = 0;
+};
+struct B {
+ virtual int bar () const = 0;
+ virtual int baz () const = 0;
+};
+struct C : public A { };
+struct D : public C { };
+struct E : public D, public B { };
+
+void
+qux (const E *x)
+{
+ if (x->baz ())
+ ;
+}
Jakub
