https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91488
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:b376b1ef38971b84975ad1540bf5d2ae0b924e76 commit r12-1603-gb376b1ef38971b84975ad1540bf5d2ae0b924e76 Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Jun 17 14:11:22 2021 +0100 libstdc++: Simplify constexpr checks in std::char_traits [PR 91488] This removes the helper functions added by r8-1294 to detect whether the char_traits member functions can be evaluated at compile time. Instead, we can just use __builtin_constant_evaluated directly, which is well supported by non-GCC compilers by now. As a result, there is a chance that those members will no longer be usable in constant expressions when using old versions of non-GCC compilers. Make the relevant feature test macros depend on the availability of __builtin_constant_evaluated, so they are defined only when the feature is actualyl available. The new testcase from the PR is added to the libitm testsuite, because that's where we can be sure it's OK to use the -fgnu-tm option. Signed-off-by: Jonathan Wakely <jwak...@redhat.com> PR libstdc++/91488 libstdc++-v3/ChangeLog: * include/bits/basic_string.h (__cpp_lib_constexpr_string): Only define when is_constant_evaluated is available. * include/bits/char_traits.h (__cpp_lib_constexpr_char_traits): Likewise. (__constant_string_p, __constant_array_p): Remove. (char_traits): Use is_constant_evaluated directly. * include/std/version (__cpp_lib_constexpr_char_traits) (__cpp_lib_constexpr_string): Only define when is_constant_evaluated is available. libitm/ChangeLog: * testsuite/libitm.c++/libstdc++-pr91488.C: New test.
