c++: [[no_unique_address]] and cv-qualified type

We were checking for overlap using same_type_p and therefore allocating two
Empty subobjects at the same offset because one was cv-qualified.

This gives the warning at the location of the class name rather than the
member declaration, but this should be a rare enough issue that it doesn't
seem worth trying to be more precise.

gcc/ChangeLog:

	* common.opt: Update -fabi-version=19.

gcc/cp/ChangeLog:

	* class.cc (check_subobject_offset): Check
	same_type_ignoring_top_level_qualifiers_p.

gcc/testsuite/ChangeLog:

	* g++.dg/abi/no_unique_address8.C: New test.
	* g++.dg/abi/no_unique_address8a.C: New test.

2 files changed, 61 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/abi/no_unique_address8.C b/gcc/testsuite/g++.dg/abi/no_unique_address8.C
new file mode 100644
index 0000000..6aa2bba
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/no_unique_address8.C
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-fabi-version=19 -Wabi=18" }
+
+#include <cstddef>
+
+#define NOUNIQUE [[no_unique_address]]
+
+struct Empty { };
+#define CHECK_DISTINCT(type, field1, field2) static_assert(offsetof(type, field1) != offsetof(type, field2))
+
+struct A1 {
+    NOUNIQUE Empty a;
+    Empty b;
+};
+CHECK_DISTINCT(A1, a, b);
+struct A2 {
+    NOUNIQUE const Empty a;
+    const Empty b;
+};
+CHECK_DISTINCT(A2, a, b);
+struct A3 {			// { dg-warning "layout" }
+    NOUNIQUE const Empty a;
+    Empty b;
+};
+CHECK_DISTINCT(A3, a, b);
+struct A4 {			// { dg-warning "layout" }
+    NOUNIQUE Empty a;
+    const Empty b;
+};
+CHECK_DISTINCT(A4, a, b);
diff --git a/gcc/testsuite/g++.dg/abi/no_unique_address8a.C b/gcc/testsuite/g++.dg/abi/no_unique_address8a.C
new file mode 100644
index 0000000..c5d4808
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/no_unique_address8a.C
@@ -0,0 +1,31 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-fabi-version=18 -Wabi=19" }
+
+#include <cstddef>
+
+#define NOUNIQUE [[no_unique_address]]
+
+struct Empty { };
+#define CHECK_DISTINCT(type, field1, field2) static_assert(offsetof(type, field1) != offsetof(type, field2))
+#define CHECK_SAME(type, field1, field2) static_assert(offsetof(type, field1) == offsetof(type, field2))
+
+struct A1 {
+    NOUNIQUE Empty a;
+    Empty b;
+};
+CHECK_DISTINCT(A1, a, b);
+struct A2 {
+    NOUNIQUE const Empty a;
+    const Empty b;
+};
+CHECK_DISTINCT(A2, a, b);
+struct A3 {			// { dg-warning "layout" }
+    NOUNIQUE const Empty a;
+    Empty b;
+};
+CHECK_SAME(A3, a, b);
+struct A4 {			// { dg-warning "layout" }
+    NOUNIQUE Empty a;
+    const Empty b;
+};
+CHECK_SAME(A4, a, b);