Hi!
On the following testcase the constexpr evaluation of the virtual call
fails, because what cxx_eval_constant_expression returns for
OBJ_TYPE_REF_OBJECT is actually not ADDR_EXPR, but ADDR_EXPR wrapped in
a NOP_EXPR.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
2019-11-27 Jakub Jelinek <ja...@redhat.com>
PR c++/92695
* constexpr.c (cxx_eval_constant_expression) <case OBJ_TYPE_REF>: Use
STRIP_NOPS before checking for ADDR_EXPR.
* g++.dg/cpp2a/constexpr-virtual15.C: New test.
--- gcc/cp/constexpr.c.jj 2019-11-27 17:53:37.477566346 +0100
+++ gcc/cp/constexpr.c 2019-11-27 21:16:51.094188509 +0100
@@ -5566,6 +5566,7 @@ cxx_eval_constant_expression (const cons
tree obj = OBJ_TYPE_REF_OBJECT (t);
obj = cxx_eval_constant_expression (ctx, obj, lval, non_constant_p,
overflow_p);
+ STRIP_NOPS (obj);
/* We expect something in the form of &x.D.2103.D.2094; get x. */
if (TREE_CODE (obj) != ADDR_EXPR
|| !DECL_P (get_base_address (TREE_OPERAND (obj, 0))))
--- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual15.C.jj 2019-11-27
21:18:15.418895652 +0100
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-virtual15.C 2019-11-27
21:17:48.602306802 +0100
@@ -0,0 +1,7 @@
+// PR c++/92695
+// { dg-do compile { target c++2a } }
+
+struct A { virtual int get() = 0; };
+struct B : A { constexpr int get() override { return 10; } };
+struct D { B b[2]; A* c{&(b[0])}; };
+static_assert(D{}.c->get() == 10);
Jakub
