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[libc++][numeric] Marked saturation artithmetic functions as [[nodiscard]] #166898

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Merged
merged 2 commits into from
Nov 9, 2025
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[libc++][numeric] Marked saturation artithmetic functions as [[nodiscard]] #166898

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[libc++][numeric] Marked saturation artithmetic functions as `[[nodis…
H-G-Hristov Nov 7, 2025
8619feb
Merge branch 'main' into hgh/libcxx/nodiscard-to-saturation-arithmetic
Zingam Nov 8, 2025
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10 changes: 5 additions & 5 deletions libcxx/include/__numeric/saturation_arithmetic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -121,27 +121,27 @@ _LIBCPP_HIDE_FROM_ABI constexpr _Rp __saturate_cast(_Tp __x) noexcept {
#if _LIBCPP_STD_VER >= 26

template <__signed_or_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
return std::__add_sat(__x, __y);
}

template <__signed_or_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
return std::__sub_sat(__x, __y);
}

template <__signed_or_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
return std::__mul_sat(__x, __y);
}

template <__signed_or_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
return std::__div_sat(__x, __y);
}

template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
return std::__saturate_cast<_Rp>(__x);
}

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35 changes: 35 additions & 0 deletions libcxx/test/libcxx/numerics/nodiscard.verify.cpp
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@@ -0,0 +1,35 @@
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

// REQUIRES: std-at-least-c++20

// <numeric>

// Check that functions are marked [[nodiscard]]

#include <bit>
#include <numeric>

#include "test_macros.h"

void test() {
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@philnik777 philnik777 Nov 7, 2025

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Let's merge this with bitops.rot/nodiscard.verify.cpp into a single numerics/nodiscard.verify.cpp These are small enough that there isn't much of a point separating them.

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@H-G-Hristov H-G-Hristov Nov 8, 2025

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Done! Thank you!

// [bit.rotate]
std::rotl(0u, 0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::rotr(0u, 0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

// clang-format off
#if TEST_STD_VER >= 26
// [numeric.sat]
std::add_sat(94, 82); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::sub_sat(94, 82); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::mul_sat(94, 82); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::div_sat(94, 82); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::saturate_cast<signed int>(49); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
#endif // TEST_STD_VER >= 26
// clang-format on
}
18 changes: 0 additions & 18 deletions libcxx/test/std/numerics/bit/bitops.rot/nodiscard.verify.cpp
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