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[libc++][math] Provide overloads for cv-unqualified floating point types for std::signbit #106566

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merged 5 commits into from
Sep 12, 2024
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[libc++][math] Provide overloads for cv-unqualified floating point types for std::signbit #106566

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7804824
Test floating point overloads
robincaloudis Sep 5, 2024
528be9e
Add floating point overloads for std::signbit
robincaloudis Sep 5, 2024
9c24e8d
Encapsulate the use of macro and leave comment
robincaloudis Sep 7, 2024
d7e4b9b
Define overloads as templates
robincaloudis Sep 11, 2024
c5f0338
Remove unused header
robincaloudis Sep 12, 2024
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18 changes: 15 additions & 3 deletions libcxx/include/__math/traits.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@
#include <__config>
#include <__type_traits/enable_if.h>
#include <__type_traits/is_arithmetic.h>
#include <__type_traits/is_floating_point.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_signed.h>
#include <__type_traits/promote.h>
Expand All @@ -34,8 +33,21 @@ namespace __math {
# define _LIBCPP_SIGNBIT_CONSTEXPR
#endif

template <class _A1, __enable_if_t<is_floating_point<_A1>::value, int> = 0>
_LIBCPP_NODISCARD inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(_A1 __x) _NOEXCEPT {
// The universal C runtime (UCRT) in the WinSDK provides floating point overloads
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// for std::signbit(). By defining our overloads as templates, we can work around
// this issue as templates are less preferred than non-template functions.
template <class = void>
_LIBCPP_NODISCARD inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(float __x) _NOEXCEPT {
return __builtin_signbit(__x);
}

template <class = void>
_LIBCPP_NODISCARD inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(double __x) _NOEXCEPT {
return __builtin_signbit(__x);
}

template <class = void>
_LIBCPP_NODISCARD inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(long double __x) _NOEXCEPT {
return __builtin_signbit(__x);
}

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13 changes: 13 additions & 0 deletions libcxx/test/std/numerics/c.math/signbit.pass.cpp
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Expand Up @@ -70,9 +70,22 @@ struct TestInt {
}
};

template <typename T>
struct ConvertibleTo {
operator T() const { return T(); }
};

int main(int, char**) {
types::for_each(types::floating_point_types(), TestFloat());
types::for_each(types::integral_types(), TestInt());

// Make sure we can call `std::signbit` with convertible types. This checks
// whether overloads for all cv-unqualified floating-point types are working
// as expected.
{
assert(!std::signbit(ConvertibleTo<float>()));
assert(!std::signbit(ConvertibleTo<double>()));
assert(!std::signbit(ConvertibleTo<long double>()));
}
return 0;
}
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