llvm-capstone/libcxx/include/latch
Mark de Wever 34933d1872
[libc++] Improves _LIBCPP_HAS_NO_THREADS guards. (#76624)
Previously the header included several headers, possibly granularized
threading headers. This could lead to build errors when these headers
were incompatible with threading disabled.

Now test the guard before inclusion. This matches the pattern used for
no localization and no wide characters.

Fixes: https://github.com/llvm/llvm-project/issues/76620
2024-01-16 19:13:40 +01:00

124 lines
3.4 KiB
C++

// -*- 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_LATCH
#define _LIBCPP_LATCH
/*
latch synopsis
namespace std
{
class latch
{
public:
static constexpr ptrdiff_t max() noexcept;
constexpr explicit latch(ptrdiff_t __expected);
~latch();
latch(const latch&) = delete;
latch& operator=(const latch&) = delete;
void count_down(ptrdiff_t __update = 1);
bool try_wait() const noexcept;
void wait() const;
void arrive_and_wait(ptrdiff_t __update = 1);
private:
ptrdiff_t __counter; // exposition only
};
}
*/
#include <__config>
#ifdef _LIBCPP_HAS_NO_THREADS
# error "<latch> is not supported since libc++ has been configured without support for threads."
#endif
#include <__assert> // all public C++ headers provide the assertion handler
#include <__atomic/atomic_base.h>
#include <__atomic/atomic_sync.h>
#include <__atomic/memory_order.h>
#include <__availability>
#include <cstddef>
#include <limits>
#include <version>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
#if _LIBCPP_STD_VER >= 14
_LIBCPP_BEGIN_NAMESPACE_STD
class latch {
__atomic_base<ptrdiff_t> __a_;
public:
static _LIBCPP_HIDE_FROM_ABI constexpr ptrdiff_t max() noexcept { return numeric_limits<ptrdiff_t>::max(); }
inline _LIBCPP_HIDE_FROM_ABI constexpr explicit latch(ptrdiff_t __expected) : __a_(__expected) {
_LIBCPP_ASSERT_UNCATEGORIZED(
__expected >= 0,
"latch::latch(ptrdiff_t): latch cannot be "
"initialized with a negative value");
_LIBCPP_ASSERT_UNCATEGORIZED(
__expected <= max(),
"latch::latch(ptrdiff_t): latch cannot be "
"initialized with a value greater than max()");
}
_LIBCPP_HIDE_FROM_ABI ~latch() = default;
latch(const latch&) = delete;
latch& operator=(const latch&) = delete;
inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void count_down(ptrdiff_t __update = 1) {
_LIBCPP_ASSERT_UNCATEGORIZED(__update >= 0, "latch::count_down called with a negative value");
auto const __old = __a_.fetch_sub(__update, memory_order_release);
_LIBCPP_ASSERT_UNCATEGORIZED(
__update <= __old,
"latch::count_down called with a value greater "
"than the internal counter");
if (__old == __update)
__a_.notify_all();
}
inline _LIBCPP_HIDE_FROM_ABI bool try_wait() const noexcept { return 0 == __a_.load(memory_order_acquire); }
inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait() const {
__cxx_atomic_wait(&__a_.__a_, [this]() -> bool { return try_wait(); });
}
inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void arrive_and_wait(ptrdiff_t __update = 1) {
_LIBCPP_ASSERT_UNCATEGORIZED(__update >= 0, "latch::arrive_and_wait called with a negative value");
// other preconditions on __update are checked in count_down()
count_down(__update);
wait();
}
};
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_STD_VER >= 14
_LIBCPP_POP_MACROS
#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
# include <atomic>
#endif
#endif //_LIBCPP_LATCH