a9c9183ca4
As discussed on cfe-dev [1], use the using_if_exists Clang attribute when the compiler supports it. This makes it easier to port libc++ on top of new platforms that don't fully support the C Standard library. Previously, libc++ would fail to build when trying to import a missing declaration in a <cXXXX> header. With the attribute, the declaration will simply not be imported into namespace std, and hence it won't be available for libc++ to use. In many cases, the declarations were *not* actually required for libc++ to work (they were only surfaced for users to use them as std::XXXX), so not importing them into namespace std is acceptable. The same thing could be achieved by conscious usage of `#ifdef` along with platform detection, however that quickly creates a maintenance problem as libc++ is ported to new platforms. Furthermore, this problem is exacerbated when mixed with vendor internal-only platforms, which can lead to difficulties maintaining a downstream fork of the library. For the time being, we only use the using_if_exists attribute when it is supported. At some point in the future, we will start removing #ifdef paths that are unnecessary when the attribute is supported, and folks who need those #ifdef paths will be required to use a compiler that supports the attribute. [1]: http://lists.llvm.org/pipermail/cfe-dev/2020-June/066038.html Differential Revision: https://reviews.llvm.org/D90257
58 lines
1.0 KiB
C++
58 lines
1.0 KiB
C++
// -*- C++ -*-
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//===--------------------------- csignal ----------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP_CSIGNAL
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#define _LIBCPP_CSIGNAL
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/*
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csignal synopsis
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Macros:
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SIG_DFL
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SIG_ERR
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SIG_IGN
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SIGABRT
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SIGFPE
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SIGILL
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SIGINT
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SIGSEGV
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SIGTERM
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namespace std
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{
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Types:
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sig_atomic_t
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void (*signal(int sig, void (*func)(int)))(int);
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int raise(int sig);
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} // std
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*/
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#include <__config>
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#include <signal.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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#pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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using ::sig_atomic_t _LIBCPP_USING_IF_EXISTS;
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using ::signal _LIBCPP_USING_IF_EXISTS;
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using ::raise _LIBCPP_USING_IF_EXISTS;
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_CSIGNAL
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