add no_unique_address macro

cf.  https://devblogs.microsoft.com/cppblog/msvc-cpp20-and-the-std-cpp20-switch/

2 files changed, 13 insertions, 5 deletions

diff --git a/compat/defs.hpp b/compat/defs.hpp
index 585c45d1..7fa74c9f 100644
--- a/compat/defs.hpp
+++ b/compat/defs.hpp
@@ -53,3 +53,11 @@
 #else
 #   define fm_noinline __attribute__((noinline))
 #endif
+
+#ifdef _MSC_VER
+// standard version not supported in MSVC v14x ABI
+// see https://devblogs.microsoft.com/cppblog/msvc-cpp20-and-the-std-cpp20-switch/
+#define fm_no_unique_address msvc::no_unique_address
+#else
+#define fm_no_unique_address no_unique_address
+#endif
diff --git a/entity/metadata.hpp b/entity/metadata.hpp
index dd82ce8a..16a4422d 100644
--- a/entity/metadata.hpp
+++ b/entity/metadata.hpp
@@ -112,11 +112,11 @@ public:
     using Length     = typename c_length::type;
 
     StringView name;
-    [[no_unique_address]] R reader;
-    [[no_unique_address]] W writer;
-    [[no_unique_address]] Predicate predicate;
-    [[no_unique_address]] Range range;
-    [[no_unique_address]] Length length;
+    [[fm_no_unique_address]] R reader;
+    [[fm_no_unique_address]] W writer;
+    [[fm_no_unique_address]] Predicate predicate;
+    [[fm_no_unique_address]] Range range;
+    [[fm_no_unique_address]] Length length;
 
     fm_DECLARE_DEFAULT_MOVE_COPY_ASSIGNMENTS(entity_field);