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Re: Fix std::byte namespace declaration

On 18/10/18 22:12 +0200, François Dumont wrote:
Current build of libstdc++ with --enable-symvers=gnu-versioned-namespace fails (at least under Linux) because of:

In file included from /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/memory_resource:39,
                 from ../../../../../git/libstdc++-v3/src/c++17/ /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/cstddef:71:59: error: la référence à « byte » est ambiguë
   71 |   template<> struct __byte_operand<bool> { using __type = byte; };
      | ^~~~
In file included from /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/stl_algobase.h:61,
                 from /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/memory:62,
                 from /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/memory_resource:37,
                 from ../../../../../git/libstdc++-v3/src/c++17/ /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/cpp_type_traits.h:395:30: note: les candidats sont : « enum class std::__8::byte »
  395 |   enum class byte : unsigned char;
      |                              ^~~~
In file included from /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/memory_resource:39,
                 from ../../../../../git/libstdc++-v3/src/c++17/ /home/fdt/dev/gcc/build_versioned_ns/x86_64-pc-linux-gnu/libstdc++-v3/include/cstddef:68:14: note:                      « enum class std::byte »
   68 |   enum class byte : unsigned char {};
      |              ^~~~

I think the issue if that std::byte declaration in cpp_type_traits.h has been done in versioned namespace, so the attached patch.

I think the definitions in <cstddef> should use the versioned
namespace macros. Then <bits/cpp_type_traits.h> would be correct.

    * include/bits/cpp_type_traits.h (std::byte): Move outside versioned

Tested under Linux x86_64.

Ok to commit ?


diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
index 960d469f412..fa7fc7564c2 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -68,6 +68,10 @@ extern "C++" {

namespace std _GLIBCXX_VISIBILITY(default)
+#if __cplusplus >= 201703L
+  enum class byte : unsigned char;

  struct __true_type { };
@@ -392,8 +396,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)

#if __cplusplus >= 201703L
-  enum class byte : unsigned char;
    struct __is_byte<byte>

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