[libcxx-commits] [libcxx] [libc++][math] Add `constexpr` to `std::fpclassify` (PR #210993)
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Tue Jul 21 09:47:15 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Lucas Mellone (lknknm)
<details>
<summary>Changes</summary>
Implement `constexpr` to `std::fpclassify` as defined by [P0533R9](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p0533r9.pdf).
Towards https://github.com/llvm/llvm-project/issues/105174. Follows-up https://github.com/llvm/llvm-project/commit/8889a3d3b5154.
---
Full diff: https://github.com/llvm/llvm-project/pull/210993.diff
5 Files Affected:
- (modified) libcxx/include/cmath (+1-1)
- (modified) libcxx/include/math.h (+4-4)
- (modified) libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp (+3-3)
- (modified) libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-gcc.pass.cpp (+3-3)
- (added) libcxx/test/std/numerics/c.math/fpclassify.pass.cpp (+79)
``````````diff
diff --git a/libcxx/include/cmath b/libcxx/include/cmath
index 208791ca0804c..992854b0490a3 100644
--- a/libcxx/include/cmath
+++ b/libcxx/include/cmath
@@ -138,7 +138,7 @@ long double tanhl(long double x);
bool signbit(arithmetic x);
-int fpclassify(arithmetic x);
+int fpclassify(arithmetic x); // constexpr since C++23
bool isfinite(arithmetic x);
bool isinf(arithmetic x);
diff --git a/libcxx/include/math.h b/libcxx/include/math.h
index 1db61538e995f..86ad9a1ae9b10 100644
--- a/libcxx/include/math.h
+++ b/libcxx/include/math.h
@@ -389,22 +389,22 @@ namespace __math {
// template on non-double overloads to make them weaker than same overloads from MSVC runtime
template <class = int>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI int fpclassify(float __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int fpclassify(float __x) _NOEXCEPT {
return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, FP_SUBNORMAL, FP_ZERO, __x);
}
template <class = int>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI int fpclassify(double __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int fpclassify(double __x) _NOEXCEPT {
return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, FP_SUBNORMAL, FP_ZERO, __x);
}
template <class = int>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI int fpclassify(long double __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int fpclassify(long double __x) _NOEXCEPT {
return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, FP_SUBNORMAL, FP_ZERO, __x);
}
template <class _A1, std::__enable_if_t<std::is_integral<_A1>::value, int> = 0>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI int fpclassify(_A1 __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int fpclassify(_A1 __x) _NOEXCEPT {
return __x == 0 ? FP_ZERO : FP_NORMAL;
}
diff --git a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
index 93865afc5e68b..926ff37cddbfc 100644
--- a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
+++ b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
@@ -203,9 +203,9 @@ int main(int, char**) {
ASSERT_NOT_CONSTEXPR_CXX23(std::fmaf(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_NOT_CONSTEXPR_CXX23(std::fmal(1.0L, 1.0L, 1.0L) == 2.0L);
- ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0f) == FP_NORMAL);
- ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0) == FP_NORMAL);
- ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0L) == FP_NORMAL);
+ ASSERT_CONSTEXPR_CXX23(std::fpclassify(-1.0f) == FP_NORMAL);
+ ASSERT_CONSTEXPR_CXX23(std::fpclassify(-1.0) == FP_NORMAL);
+ ASSERT_CONSTEXPR_CXX23(std::fpclassify(-1.0L) == FP_NORMAL);
ASSERT_CONSTEXPR_CXX23(std::isfinite(-1.0f) == 1);
ASSERT_CONSTEXPR_CXX23(std::isfinite(-1.0) == 1);
diff --git a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-gcc.pass.cpp b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-gcc.pass.cpp
index d8779706bcee2..455c03ef58d18 100644
--- a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-gcc.pass.cpp
+++ b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-gcc.pass.cpp
@@ -197,9 +197,9 @@ int main(int, char**) {
ASSERT_CONSTEXPR_CXX23(std::fmaf(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_CONSTEXPR_CXX23(std::fmal(1.0L, 1.0L, 1.0L) == 2.0L);
- ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0f) == FP_NORMAL);
- ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0) == FP_NORMAL);
- ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0L) == FP_NORMAL);
+ ASSERT_CONSTEXPR_CXX23(std::fpclassify(-1.0f) == FP_NORMAL);
+ ASSERT_CONSTEXPR_CXX23(std::fpclassify(-1.0) == FP_NORMAL);
+ ASSERT_CONSTEXPR_CXX23(std::fpclassify(-1.0L) == FP_NORMAL);
ASSERT_CONSTEXPR_CXX23(std::isfinite(-1.0f) == 1);
ASSERT_CONSTEXPR_CXX23(std::isfinite(-1.0) == 1);
diff --git a/libcxx/test/std/numerics/c.math/fpclassify.pass.cpp b/libcxx/test/std/numerics/c.math/fpclassify.pass.cpp
new file mode 100644
index 0000000000000..fda9f28a1389f
--- /dev/null
+++ b/libcxx/test/std/numerics/c.math/fpclassify.pass.cpp
@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// bool fpclassify(floating-point-type x); // constexpr since C++23
+
+#include <cassert>
+#include <cmath>
+#include <limits>
+#include <type_traits>
+
+#include "test_macros.h"
+#include "type_algorithms.h"
+
+struct TestFloat {
+ template <class T>
+ static TEST_CONSTEXPR_CXX23 bool test() {
+ assert(std::fpclassify(std::numeric_limits<T>::quiet_NaN()) == FP_NAN);
+ assert(std::fpclassify(std::numeric_limits<T>::signaling_NaN()) == FP_NAN);
+
+ assert(std::fpclassify(std::numeric_limits<T>::infinity()) == FP_INFINITE);
+ assert(std::fpclassify(-std::numeric_limits<T>::infinity()) == FP_INFINITE);
+
+ assert(std::fpclassify(T(1)) == FP_NORMAL);
+ assert(std::fpclassify(T(-1)) == FP_NORMAL);
+ assert(std::fpclassify(std::numeric_limits<T>::max()) == FP_NORMAL);
+ assert(std::fpclassify(std::numeric_limits<T>::min()) == FP_NORMAL);
+
+ assert(std::fpclassify(std::numeric_limits<T>::denorm_min()) == FP_SUBNORMAL);
+
+ assert(std::fpclassify(T(0)) == FP_ZERO);
+ assert(std::fpclassify(T(-0.0)) == FP_ZERO);
+
+ return true;
+ }
+
+ template <class T>
+ TEST_CONSTEXPR_CXX23 void operator()() {
+ test<T>();
+#if TEST_STD_VER >= 23
+ static_assert(test<T>());
+#endif
+ }
+};
+
+struct TestInt {
+ template <class T>
+ static TEST_CONSTEXPR_CXX23 bool test() {
+ assert(std::fpclassify(T(0)) == FP_ZERO);
+ assert(std::fpclassify(T(1)) == FP_NORMAL);
+ assert(std::fpclassify(std::numeric_limits<T>::max()) == FP_NORMAL);
+
+ if (std::is_signed<T>::value) {
+ assert(std::fpclassify(std::numeric_limits<T>::lowest()) == FP_NORMAL);
+ assert(std::fpclassify(T(-1)) == FP_NORMAL);
+ }
+
+ return true;
+ }
+
+ template <class T>
+ TEST_CONSTEXPR_CXX23 void operator()() {
+ test<T>();
+#if TEST_STD_VER >= 23
+ static_assert(test<T>());
+#endif
+ }
+};
+
+int main(int, char**) {
+ types::for_each(types::floating_point_types(), TestFloat());
+ types::for_each(types::integral_types(), TestInt());
+
+ return 0;
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/210993
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