libkern/os/ptrtools.h

   1 /* * Copyright (c) 2018 Apple Inc. All rights reserved.
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   3  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
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   5  * This file contains Original Code and/or Modifications of Original Code
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   7  * Version 2.0 (the 'License'). You may not use this file except in
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  14  * Please obtain a copy of the License at
  15  * http://www.opensource.apple.com/apsl/ and read it before using this file.
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  17  * The Original Code and all software distributed under the License are
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  27
  28 #ifndef _OS_PTRTOOLS_H
  29 #define _OS_PTRTOOLS_H
  30
  31 /* dereference unaligned pointer 'p' */
  32 #define os_unaligned_deref(p) ((__os_unaligned_type(p))(p))->val
  33
  34 /* ensure the compiler emits at most one access to 'val' */
  35 #define os_access_once(val) (*((volatile __typeof__((val)) *)&(val)))
  36
  37 #define __os_unaligned_type(p) struct { __typeof__(*(p)) val; } __attribute__((packed)) *
  38
  39 #endif /* _OS_PTRTOOLS_H */