Fixes LWG3656, "Inconsistent bit operations returning a count".
https://cplusplus.github.io/LWG/issue3656
The fix has been approved for C++23 and left to vendors' discretion
in C++20 (but it sounds like everyone's on the same page that
of course it should be DR'ed back to C++20 too).
Differential Revision: https://reviews.llvm.org/D120444
This avoids using an libc++ internal macro in our tests. This version
doesn't depend on the internal macro but redefines it.
Reviewed By: #libc, ldionne
Differential Revision: https://reviews.llvm.org/D119460
Fix __bitop_unsigned_integer and rename to __libcpp_is_unsigned_integer.
There are only five unsigned integer types, so we should just list them out.
Also provide `__libcpp_is_signed_integer`, even though the Standard doesn't
consume that trait anywhere yet.
Notice that `concept uniform_random_bit_generator` is specifically specified
to rely on `concept unsigned_integral` and *not* `__is_unsigned_integer`.
Instantiating `std::ranges::sample` with a type `U` satisfying
`uniform_random_bit_generator` where `unsigned_integral<U::result_type>`
and not `__is_unsigned_integer<U::result_type>` is simply IFNDR.
Orthogonally, fix an undefined behavior in std::countr_zero(__uint128_t).
Orthogonally, improve tests for the <bit> manipulation functions.
It was these new tests that detected the bug in countr_zero.
Differential Revision: https://reviews.llvm.org/D102328
Implements P1956: On the names of low-level bit manipulation functions.
Users may use older versions of libc++ or other standard libraries with the old names. In order to keep compatibility the old functions are kept, but marked as deprecated.
The patch also adds a new config macro `_LIBCPP_DEPRECATED_MSG`. Do you prefer a this is a separate patch?
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D90551
Arthur O'Dwyer