https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114118
Bug ID: 114118
Summary: std::is_floating_point<_Float32> and
__is_floating<_Float32> are false in C++20 and older
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
Since GCC 13 we defined _Float32 etc. as distinct types, but the library only
considers them to be floating-point types for C++23 and later, when <stdfloat>
declares the aliases std::float32_t etc.
This means that the proposed solution for PR 114018 only works in C++23:
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3790. P1467 accidentally changed nexttoward's signature
template<typename _Tp>
typename __gnu_cxx::__enable_if<__is_floating<_Tp>::__value, _Tp>::__type
nexttoward(_Tp, long double) = delete; // not defined for extended FP types
For C++20 std::nexttoward(_Float32(0), 0.0L) compiles and selects the float
overload.
To consistently delete them we would need to do:
#if __FLT32_DIG__
void nexttoward(_Float32, long double) = delete;
#endif
We should probably just make __is_floating<_Float32> true for all -std modes.
And also define __gnu_cxx::__numeric_traits<_Float32>.
