[gcc r15-4266] libstdc++: Use appropriate feature test macro for std::byte

[Jonathan Wakely via Libstdc++-cvs]

https://gcc.gnu.org/g:00a87ee76f47d0fa5a10ef982101cb3c3b8e9c99

commit r15-4266-g00a87ee76f47d0fa5a10ef982101cb3c3b8e9c99
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Fri Oct 11 13:29:06 2024 +0100

    libstdc++: Use appropriate feature test macro for std::byte
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/cpp_type_traits.h (__is_byte<byte>): Guard with
            __glibcxx_byte macro instead of checking __cplusplus.

Diff:
---
 libstdc++-v3/include/bits/cpp_type_traits.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h 
b/libstdc++-v3/include/bits/cpp_type_traits.h
index 19bf1edf647e..060652afb183 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -414,7 +414,7 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
       typedef __true_type __type;
     };
 
-#if __cplusplus >= 201703L
+#ifdef __glibcxx_byte // C++ >= 17
   enum class byte : unsigned char;
 
   template<>