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libstdc++: Use __cpp_concepts instead of custom macro [PR103891] 

With the new value of __cpp_concepts required by P2493, we can test
whether the compiler supports conditionally trivial special members.
This allows us to remove the workaround that disables fully-constexpr
std::variant for Clang. Now it should work for non-GCC compilers (such
as future releases of Clang) that support conditionally trivial
destructors and define the new value of __cpp_concepts.

libstdc++-v3/ChangeLog:

	PR libstdc++/103891
	* include/bits/c++config (_GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS):
	Remove.
	* include/std/variant: Check feature test macros instead.
	* include/std/version: Likewise.
This commit is contained in:
Jonathan Wakely 2022-02-14 12:46:10 +00:00
parent 220d85fdf0
commit 164a761a9f
3 changed files with 10 additions and 17 deletions
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5
libstdc++-v3/include/bits/c++config
View File

@ -810,11 +810,6 @@ namespace std
#undef _GLIBCXX_HAS_BUILTIN
#if __cplusplus >= 202002L && __cpp_concepts && __GNUC__ >= 12
// XXX workaround for missing feature test macro for P0848R3 (see P2493R0).
# define _GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS 1
#endif
// PSTL configuration
#if __cplusplus >= 201703L

18
libstdc++-v3/include/std/variant
View File

@ -44,24 +44,22 @@
#include <bits/stl_iterator_base_funcs.h>
#include <bits/stl_construct.h>
#include <bits/utility.h> // in_place_index_t
#ifndef _GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS
# include <ext/aligned_buffer.h>
#endif
#if __cplusplus >= 202002L
# include <compare>
#endif
#if __cpp_concepts >= 202002L && __cpp_constexpr >= 201811L
// P2231R1 constexpr needs constexpr unions and constrained destructors.
# define __cpp_lib_variant 202106L
#else
# include <ext/aligned_buffer.h> // Use __aligned_membuf instead of union.
# define __cpp_lib_variant 202102L
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef _GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS
// P2231R1 constexpr needs constexpr unions and constrained destructors.
# define __cpp_lib_variant 202106L
#else
# define __cpp_lib_variant 202102L
#endif
template<typename... _Types> class tuple;
template<typename... _Types> class variant;
template <typename> struct hash;

4
libstdc++-v3/include/std/version
View File

@ -175,7 +175,7 @@
# define __cpp_lib_to_chars 201611L
#endif
#define __cpp_lib_unordered_map_try_emplace 201411L
#ifndef _GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS
#if !(__cplusplus >= 202002L && __cpp_concepts >= 202002L)
// N.B. updated value in C++20
# define __cpp_lib_variant 202102L
#endif
@ -292,7 +292,7 @@
# endif
#define __cpp_lib_to_address 201711L
#define __cpp_lib_to_array 201907L
#ifdef _GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS
#if __cplusplus >= 202002L && __cpp_concepts >= 202002L
# define __cpp_lib_variant 202106L
#endif
#endif