output_constructor doesn't like two consecutive entries with fields at the
same position; let's avoid adding the one for the empty field.
Tested x86_64-pc-linux-gnu, applying to trunk and 9.
gcc/cp/ChangeLog
2020-03-04 Jason Merrill <ja...@redhat.com>
PR c++/90432
* init.c (perform_member_init): Don't do aggregate initialization of
empty field.
* constexpr.c (cx_check_missing_mem_inits): Don't enforce
initialization of empty field.
---
gcc/cp/constexpr.c | 3 +++
gcc/cp/init.c | 5 +++++
gcc/testsuite/g++.dg/cpp2a/no_unique_address3.C | 16 ++++++++++++++++
3 files changed, 24 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/no_unique_address3.C
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index c2d44605764..521c87f6210 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -831,6 +831,9 @@ cx_check_missing_mem_inits (tree ctype, tree body, bool
complain)
/* A flexible array can't be intialized here, so don't complain
that it isn't. */
continue;
+ if (DECL_SIZE (field) && integer_zerop (DECL_SIZE (field)))
+ /* An empty field doesn't need an initializer. */
+ continue;
ftype = strip_array_types (ftype);
if (type_has_constexpr_default_constructor (ftype))
{
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 61ed3aa7e93..27623cf4db1 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -865,6 +865,11 @@ perform_member_init (tree member, tree init)
}
if (init == error_mark_node)
return;
+ if (DECL_SIZE (member) && integer_zerop (DECL_SIZE (member))
+ && !TREE_SIDE_EFFECTS (init))
+ /* Don't add trivial initialization of an empty base/field, as they
+ might not be ordered the way the back-end expects. */
+ return;
/* A FIELD_DECL doesn't really have a suitable lifetime, but
make_temporary_var_for_ref_to_temp will treat it as automatic and
set_up_extended_ref_temp wants to use the decl in a warning. */
diff --git a/gcc/testsuite/g++.dg/cpp2a/no_unique_address3.C
b/gcc/testsuite/g++.dg/cpp2a/no_unique_address3.C
new file mode 100644
index 00000000000..07108b8b715
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/no_unique_address3.C
@@ -0,0 +1,16 @@
+// PR c++/90432
+// { dg-do compile { target c++11 } }
+
+struct empty {};
+
+struct has_empty {
+ [[no_unique_address]] empty brace_or_equal_initialized{};
+};
+
+struct has_value {
+ int non_zero = 1;
+};
+
+struct pair : has_empty, has_value {};
+
+pair a;
base-commit: 10bbbb591cfe6cac200e926a73f3b8065147ce84
--
2.18.1
