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
96 lines
2.8 KiB
C++
96 lines
2.8 KiB
C++
// -*- C++ -*-
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//===---------------------------- ctime -----------------------------------===//
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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_CTIME
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#define _LIBCPP_CTIME
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/*
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ctime synopsis
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Macros:
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NULL
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CLOCKS_PER_SEC
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TIME_UTC // C++17
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namespace std
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{
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Types:
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clock_t
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size_t
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time_t
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tm
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timespec // C++17
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clock_t clock();
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double difftime(time_t time1, time_t time0);
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time_t mktime(tm* timeptr);
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time_t time(time_t* timer);
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char* asctime(const tm* timeptr);
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char* ctime(const time_t* timer);
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tm* gmtime(const time_t* timer);
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tm* localtime(const time_t* timer);
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size_t strftime(char* restrict s, size_t maxsize, const char* restrict format,
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const tm* restrict timeptr);
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int timespec_get( struct timespec *ts, int base); // C++17
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} // std
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*/
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#include <__config>
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#include <time.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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// FIXME:
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// Apple SDKs don't define ::timespec_get unconditionally in C++ mode. This
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// should be fixed in future SDKs, but for the time being we need to avoid
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// trying to use that declaration when the SDK doesn't provide it. Note that
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// we're detecting this here instead of in <__config> because we can't include
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// system headers from <__config>, since it leads to circular module dependencies.
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// This is also meant to be a very temporary workaround until the SDKs are fixed.
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#if defined(__APPLE__)
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# include <sys/cdefs.h>
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# if defined(_LIBCPP_HAS_TIMESPEC_GET) && (__DARWIN_C_LEVEL < __DARWIN_C_FULL)
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# define _LIBCPP_HAS_TIMESPEC_GET_NOT_ACTUALLY_PROVIDED
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# endif
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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using ::clock_t _LIBCPP_USING_IF_EXISTS;
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using ::size_t _LIBCPP_USING_IF_EXISTS;
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using ::time_t _LIBCPP_USING_IF_EXISTS;
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using ::tm _LIBCPP_USING_IF_EXISTS;
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#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_TIMESPEC_GET)
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using ::timespec _LIBCPP_USING_IF_EXISTS;
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#endif
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using ::clock _LIBCPP_USING_IF_EXISTS;
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using ::difftime _LIBCPP_USING_IF_EXISTS;
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using ::mktime _LIBCPP_USING_IF_EXISTS;
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using ::time _LIBCPP_USING_IF_EXISTS;
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#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
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using ::asctime _LIBCPP_USING_IF_EXISTS;
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using ::ctime _LIBCPP_USING_IF_EXISTS;
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using ::gmtime _LIBCPP_USING_IF_EXISTS;
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using ::localtime _LIBCPP_USING_IF_EXISTS;
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#endif
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using ::strftime _LIBCPP_USING_IF_EXISTS;
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#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_TIMESPEC_GET) && !defined(_LIBCPP_HAS_TIMESPEC_GET_NOT_ACTUALLY_PROVIDED)
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using ::timespec_get _LIBCPP_USING_IF_EXISTS;
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#endif
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_CTIME
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