On 28/04/21 16:14 +0100, Jonathan Wakely wrote:
As noted in r11-1339-gb6ab9ecd550227684643b41e9e33a4d3466724d8 we define a non-standard __cpp_lib_constexpr_char_traits feature test macro to indicate support for P0426R1 and P1032R1. At some point last year the __cpp_lib_constexpr_string macro was retconned to indicate support for those papers. This adds the new macro (which we didn't previously define, because it referred to P0980R1 "Making std::string constexpr" which we don't support).libstdc++-v3/ChangeLog: * include/bits/basic_string.h (__cpp_lib_constexpr_string): Define. * include/std/version (__cpp_lib_constexpr_string): Define. * testsuite/21_strings/char_traits/requirements/constexpr_functions_c++17.cc: Check for __cpp_lib_constexpr_string. * testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc: Likewise. * testsuite/21_strings/char_traits/requirements/version.cc: New test.
I messed up the __cpp_lib_constexpr_string macro by copy&pasting from the __cpp_lib_constexpr_char_traits one, which is defined inside a #ifdef __cplusplus >= 201702 block. But for __cpp_lib_constexpr_string it isn't so the #else means that we define it to 201811L for everything newer *or* older than C++17. I also noticed that __cpp_lib_semaphore wasn't defined consistently, as it's failing on AIX. Fixed on trunk by this patch. Tested x86_64-linux and powerpc-aix. I'll backport this to the relevant branches too.
commit 3215d4f5b3d08e0087a88df9e155c779927ace1a Author: Jonathan Wakely <[email protected]> Date: Fri Apr 30 20:32:05 2021 libstdc++: Fix inconsistent feature test macros The __cpp_lib_constexpr_string and __cpp_lib_semaphore feature test macros are not defined consistently in <version> and the relevant header for the feature. libstdc++-v3/ChangeLog: * include/bits/basic_string.h (__cpp_lib_constexpr_string): Only define for C++17 and later. * include/std/version (__cpp_lib_semaphore): Fix condition to match the one in <semaphore>. diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index 41d781c698e..fba7c6f3354 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -55,7 +55,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #if __cplusplus == 201703L // Support P0426R1 changes to char_traits in C++17. # define __cpp_lib_constexpr_string 201611L -#else +#elif __cplusplus > 201703L // Also support P1032R1 in C++20 (but not P0980R1 yet). # define __cpp_lib_constexpr_string 201811L #endif diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version index 09e67a40d0c..ea0e18a3f9d 100644 --- a/libstdc++-v3/include/std/version +++ b/libstdc++-v3/include/std/version @@ -241,7 +241,7 @@ #if __cpp_lib_concepts # define __cpp_lib_ranges 201911L #endif -#if __cpp_lib_atomic_wait +#if __cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE # define __cpp_lib_semaphore 201907L #endif #define __cpp_lib_shift 201806L
