On 02/25/2016 09:08 AM, Jason Merrill wrote:
We don't bother evaluating a store to an empty class member, and we
shouldn't complain about accesses either.
This needs to use really_empty_class, since that's what
expand_aggr_init_1 uses.
Tested x86_64-pc-linux-gnu, applying to trunk and 5.
commit 9a1d6b7c9fa018033ff444829ad3c597e61f5120
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Mar 2 14:33:54 2016 -0500
PR c++/67364
* constexpr.c (cxx_eval_component_reference): Just return an empty
CONSTRUCTOR for an empty class.
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index bcb129f..5a81469 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1988,11 +1988,12 @@ cxx_eval_component_reference (const constexpr_ctx *ctx, tree t,
}
if (CONSTRUCTOR_NO_IMPLICIT_ZERO (whole)
- && !is_empty_class (TREE_TYPE (part)))
+ && !is_really_empty_class (TREE_TYPE (t)))
{
/* 'whole' is part of the aggregate initializer we're currently
building; if there's no initializer for this member yet, that's an
- error. */
+ error. But expand_aggr_init_1 doesn't bother to initialize really
+ empty classes, so ignore them here, too. */
if (!ctx->quiet)
error ("accessing uninitialized member %qD", part);
*non_constant_p = true;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C
new file mode 100644
index 0000000..7437367
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C
@@ -0,0 +1,17 @@
+// PR c++/67364
+// { dg-do compile { target c++11 } }
+
+template <typename Xn>
+struct element : Xn {
+ constexpr element() : Xn() { }
+};
+
+template <typename Xn>
+struct closure {
+ element<Xn> member;
+ constexpr closure() { }
+};
+
+struct empty { struct {} s; };
+constexpr closure<empty> tup{};
+constexpr empty first = tup.member;
