1 //===-- Linux futex related definitions -------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_LIBC_SRC_THREADS_LINUX_FUTEX_H
10 #define LLVM_LIBC_SRC_THREADS_LINUX_FUTEX_H
11 
12 #include <stdatomic.h>
13 
14 namespace __llvm_libc {
15 
16 // The futex data has to be exactly 4 bytes long. However, we use a uint type
17 // here as we do not want to use `_Atomic uint32_t` as the _Atomic keyword which
18 // is C only. The header stdatomic.h does not define an atomic type
19 // corresponding to `uint32_t` or to something which is exactly 4 bytes wide.
20 using FutexWord = atomic_uint;
21 static_assert(sizeof(atomic_uint) == 4,
22               "Size of the `atomic_uint` type is not 4 bytes on your platform. "
23               "The implementation of the standard threads library for linux "
24               "requires that size of `atomic_uint` be 4 bytes.");
25 
26 } // namespace __llvm_libc
27 
28 #endif // LLVM_LIBC_SRC_THREADS_LINUX_FUTEX_H
29