[committed] libstdc++: Add feature test macro for

[Jonathan Wakely via Gcc-patches]

I forgot to add this macro to the new header.

Tested x86_64-linux, pushed to trunk.

-- >8 --

libstdc++-v3/ChangeLog:

        * include/experimental/scope (__cpp_lib_experimental_scope):
        Define.
        * testsuite/experimental/scopeguard/uniqueres.cc: Check macro.
---
 libstdc++-v3/include/experimental/scope                     | 2 ++
 libstdc++-v3/testsuite/experimental/scopeguard/uniqueres.cc | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/libstdc++-v3/include/experimental/scope 
b/libstdc++-v3/include/experimental/scope
index 37a57b38af7..208fadc513e 100644
--- a/libstdc++-v3/include/experimental/scope
+++ b/libstdc++-v3/include/experimental/scope
@@ -43,6 +43,8 @@ namespace std _GLIBCXX_VISIBILITY(default)
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 namespace experimental::inline fundamentals_v3
 {
+#define __cpp_lib_experimental_scope 201902
+
   template<typename _Tp, typename _Up>
     concept __not_same_as = !same_as<_Tp, _Up>;
 
diff --git a/libstdc++-v3/testsuite/experimental/scopeguard/uniqueres.cc 
b/libstdc++-v3/testsuite/experimental/scopeguard/uniqueres.cc
index 7690572ab19..fe9d6ee7cfc 100644
--- a/libstdc++-v3/testsuite/experimental/scopeguard/uniqueres.cc
+++ b/libstdc++-v3/testsuite/experimental/scopeguard/uniqueres.cc
@@ -4,6 +4,12 @@
 #include <experimental/scope>
 #include <testsuite_hooks.h>
 
+#ifndef __cpp_lib_experimental_scope
+# error Feature-test macro is not defined.
+#elif __cpp_lib_experimental_scope < 201902
+# error Feature-test macro has bad value.
+#endif
+
 using std::experimental::unique_resource;
 
 void
-- 
2.37.1