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Fix include logic for <bit> and assert 0 and NAN when no bit_cast

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This commit is contained in:
Matt Borland
2022-08-22 18:53:11 -07:00
parent 2bd2859660
commit 48edf590f4
2 changed files with 20 additions and 23 deletions
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39
include/boost/math/ccmath/signbit.hpp
View File

@@ -11,22 +11,27 @@
#include <limits>
#include <type_traits>
#include <boost/math/tools/is_constant_evaluated.hpp>
#include <boost/math/tools/assert.hpp>
#include <boost/math/special_functions/detail/fp_traits.hpp>
#include <boost/math/ccmath/isnan.hpp>
#include <boost/math/ccmath/abs.hpp>
#if __cpp_lib_bit_cast >= 201806L
#include <bit>
# define BOOST_MATH_BIT_CAST(T, x) std::bit_cast<T>(x)
#elif defined(__has_builtin)
# if __has_builtin(__builtin_bit_cast)
# define BOOST_MATH_BIT_CAST(T, x) __builtin_bit_cast(T, x)
#ifdef __has_include
# if __has_include(<bit>)
# include <bit>
# if __cpp_lib_bit_cast >= 201806L
# define BOOST_MATH_BIT_CAST(T, x) std::bit_cast<T>(x)
# endif
# elif defined(__has_builtin)
# if __has_builtin(__builtin_bit_cast)
# define BOOST_MATH_BIT_CAST(T, x) __builtin_bit_cast(T, x)
# endif
# endif
#endif
/*
The following error is given using Apple Clang version 13.1.6
TODO: Remove the following undef when Clang supports
The following error is given using Apple Clang version 13.1.6, and Clang 13, and 14 on Ubuntu 22.04.01
TODO: Remove the following undef when Apple Clang supports
ccmath_signbit_test.cpp:32:19: error: static_assert expression is not an integral constant expression
static_assert(boost::math::ccmath::signbit(T(-1)) == true);
@@ -159,11 +164,9 @@ constexpr bool signbit_impl(T arg)
#endif
else
{
if (boost::math::ccmath::isnan(arg))
{
return false;
}
BOOST_MATH_ASSERT_MSG(!boost::math::ccmath::isnan(arg), "NAN is not supported with this type or platform");
BOOST_MATH_ASSERT_MSG(boost::math::ccmath::abs(arg) != 0, "Signed 0 is not support with this type or platform");
return arg < static_cast<T>(0);
}
}
@@ -173,16 +176,14 @@ constexpr bool signbit_impl(T arg)
// Typical implementations of signbit involve type punning via union and manipulating
// overflow (see libc++ or musl). Neither of these are allowed in constexpr contexts
// (technically type punning via union in general is UB in c++ but well defined in C)
// therefore NANs and 0s are treated as positive if bit cast is unavailable
// therefore we static assert these cases.
template <typename T>
constexpr bool signbit_impl(T arg)
{
if (boost::math::ccmath::isnan(arg))
{
return false;
}
BOOST_MATH_ASSERT_MSG(!boost::math::ccmath::isnan(arg), "NAN is not supported without __builtin_bit_cast or std::bit_cast");
BOOST_MATH_ASSERT_MSG(boost::math::ccmath::abs(arg) != 0, "Signed 0 is not support without __builtin_bit_cast or std::bit_cast");
return arg < static_cast<T>(0);
}

4
test/ccmath_signbit_test.cpp
View File

@@ -20,10 +20,6 @@ void test()
static_assert(boost::math::ccmath::signbit(std::numeric_limits<T>::signaling_NaN()) == false);
static_assert(boost::math::ccmath::signbit(-std::numeric_limits<T>::signaling_NaN()) == true);
#else
static_assert(boost::math::ccmath::signbit(T(0)) == false);
static_assert(boost::math::ccmath::signbit(std::numeric_limits<T>::quiet_NaN()) == false);
static_assert(boost::math::ccmath::signbit(std::numeric_limits<T>::signaling_NaN()) == false);
#endif
// Positive numbers