Tested powerpc64le-linux, pushed to trunk.
-- >8--
We actually defined this macro in <utility> at one point, but I removed
it in r10-7901-g2025db692e9ed1.
libstdc++-v3/ChangeLog:
* include/std/utility (__cpp_lib_constexpr_algorithms): Define,
as per LWG 3792.
* testsuite/20_util/exchange/constexpr.cc: Check for it.
---
libstdc++-v3/include/std/utility | 4 ++++
libstdc++-v3/testsuite/20_util/exchange/constexpr.cc | 6 ++++++
2 files changed, 10 insertions(+)
diff --git a/libstdc++-v3/include/std/utility b/libstdc++-v3/include/std/utility
index 43d8765228c..006b19c00fc 100644
--- a/libstdc++-v3/include/std/utility
+++ b/libstdc++-v3/include/std/utility
@@ -86,6 +86,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus >= 201402L
#define __cpp_lib_exchange_function 201304L
+#if __cplusplus > 201703L
+# define __cpp_lib_constexpr_algorithms 201806L
+#endif
+
/// Assign @p __new_val to @p __obj and return its previous value.
template <typename _Tp, typename _Up = _Tp>
_GLIBCXX20_CONSTEXPR
diff --git a/libstdc++-v3/testsuite/20_util/exchange/constexpr.cc
b/libstdc++-v3/testsuite/20_util/exchange/constexpr.cc
index 6c130f772f8..2ec13044681 100644
--- a/libstdc++-v3/testsuite/20_util/exchange/constexpr.cc
+++ b/libstdc++-v3/testsuite/20_util/exchange/constexpr.cc
@@ -20,6 +20,12 @@
#include <utility>
+#ifndef __cpp_lib_constexpr_algorithms
+# error "Feature test macro for constexpr std::exchange is missing in
<utility>"
+#elif __cpp_lib_constexpr_algorithms < 201806L
+# error "Feature test macro for constexpr std::exchange has wrong value in
<utility>"
+#endif
+
constexpr bool
test()
{
--
2.39.2
