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[libc++] Add [[clang::lifetimebound]] to std::identity #165854

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Merged
merged 1 commit into from
Nov 2, 2025
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[libc++] Add [[clang::lifetimebound]] to std::identity #165854

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2 changes: 1 addition & 1 deletion libcxx/include/__functional/identity.h
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ struct __is_identity<reference_wrapper<const __identity> > : true_type {};

struct identity {
template <class _Tp>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp&& operator()(_Tp&& __t) const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp&& operator()(_LIBCPP_LIFETIMEBOUND _Tp&& __t) const noexcept {
return std::forward<_Tp>(__t);
}

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20 changes: 20 additions & 0 deletions libcxx/test/libcxx/utilities/function.objects/lifetimebound.verify.cpp
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@@ -0,0 +1,20 @@
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14, c++17
// ADDITIONAL_COMPILE_FLAGS: -Wno-pessimizing-move -Wno-unused-variable

#include <functional>

#include "test_macros.h"

// clang-format off

void func() {
auto&& v1 = std::identity()(1); // expected-warning {{temporary bound to local reference 'v1' will be destroyed at the end of the full-expression}}
}
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