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Diffstat (limited to 'libcxx/include/__function_like.h')
-rw-r--r-- | libcxx/include/__function_like.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/libcxx/include/__function_like.h b/libcxx/include/__function_like.h new file mode 100644 index 000000000000..8a3597bacdcd --- /dev/null +++ b/libcxx/include/__function_like.h @@ -0,0 +1,56 @@ +// -*- C++ -*- +//===----------------------------------------------------------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// + +#ifndef _LIBCPP___ITERATOR_FUNCTION_LIKE_H +#define _LIBCPP___ITERATOR_FUNCTION_LIKE_H + +#include <__config> + +#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) +#pragma GCC system_header +#endif + +_LIBCPP_PUSH_MACROS +#include <__undef_macros> + +_LIBCPP_BEGIN_NAMESPACE_STD + +#if !defined(_LIBCPP_HAS_NO_RANGES) + +namespace ranges { +// Per [range.iter.ops.general] and [algorithms.requirements], functions in namespace std::ranges +// can't be found by ADL and inhibit ADL when found by unqualified lookup. The easiest way to +// facilitate this is to use function objects. +// +// Since these are still standard library functions, we use `__function_like` to eliminate most of +// the properties that function objects get by default (e.g. semiregularity, addressability), to +// limit the surface area of the unintended public interface, so as to curb the effect of Hyrum's +// law. +struct __function_like { + __function_like() = delete; + __function_like(__function_like const&) = delete; + __function_like& operator=(__function_like const&) = delete; + + void operator&() const = delete; + + struct __tag { }; + +protected: + constexpr explicit __function_like(__tag) noexcept {} + ~__function_like() = default; +}; +} // namespace ranges + +#endif // !defined(_LIBCPP_HAS_NO_RANGES) + +_LIBCPP_END_NAMESPACE_STD + +_LIBCPP_POP_MACROS + +#endif // _LIBCPP___ITERATOR_FUNCTION_LIKE_H |