1 /* 2 * Copyright (c) 2021 Apple Inc. All rights reserved. 3 * 4 * @APPLE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. Please obtain a copy of the License at 10 * http://www.opensource.apple.com/apsl/ and read it before using this 11 * file. 12 * 13 * The Original Code and all software distributed under the License are 14 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 15 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 16 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 18 * Please see the License for the specific language governing rights and 19 * limitations under the License. 20 * 21 * @APPLE_LICENSE_HEADER_END@ 22 */ 23 24 #ifndef _OS_ALLOC_UTIL_H 25 #define _OS_ALLOC_UTIL_H 26 27 #include <sys/cdefs.h> 28 #if defined(__cplusplus) && __cplusplus >= 201103L 29 extern "C++" { 30 #include <os/cpp_util.h> 31 } 32 #endif 33 34 /*! 35 * @macro os_is_ptr_like 36 * 37 * @abstract 38 * Tell whether the given expression resembles a pointer. 39 * 40 * @discussion 41 * When pointer bounds are enabled, only types that are actually classified 42 * as pointers will be considered pointer-like. Otherwise, any pointer-sized 43 * type will be considered pointer-like. 44 * 45 * @param P the expression to be checked 46 */ 47 #if __has_ptrcheck 48 #define os_is_ptr_like(P) (__builtin_classify_type(P) == 5) 49 #else /* __has_ptrcheck */ 50 #define os_is_ptr_like(P) (sizeof(P) == sizeof(void *)) 51 #endif /* __has_ptrcheck */ 52 53 /*! 54 * @macro os_ptr_load_and_erase 55 * 56 * @abstract 57 * Load the value of @c elem into a temporary, set @c elem to NULL, and 58 * return the value. 59 * 60 * @param elem the pointer whose value will be taken, and which will 61 * be set to NULL. 62 */ 63 #define os_ptr_load_and_erase(elem) ({ \ 64 _Static_assert(os_is_ptr_like(elem), \ 65 "elem isn't pointer sized"); \ 66 __auto_type *__single __eptr = &(elem); \ 67 __auto_type __elem = *__eptr; \ 68 _Pragma("clang diagnostic push") \ 69 _Pragma("clang diagnostic ignored \"-Wold-style-cast\"") \ 70 *__eptr = (__typeof__(__elem))NULL; \ 71 _Pragma("clang diagnostic pop") \ 72 __elem; \ 73 }) 74 75 #endif /* _OS_ALLOC_UTIL_H */ 76