include/urcu/compiler.h

   1 // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 //
   3 // SPDX-License-Identifier: LGPL-2.1-or-later
   4
   5 #ifndef _URCU_COMPILER_H
   6 #define _URCU_COMPILER_H
   7
   8 /*
   9  * Compiler definitions.
  10  */
  11
  12 #include <stddef.h>     /* for offsetof */
  13
  14 #if defined __cplusplus
  15 # include <type_traits> /* for std::remove_cv */
  16 #endif
  17
  18 #define caa_likely(x)   __builtin_expect(!!(x), 1)
  19 #define caa_unlikely(x) __builtin_expect(!!(x), 0)
  20
  21 #define cmm_barrier()   __asm__ __volatile__ ("" : : : "memory")
  22
  23 /*
  24  * Instruct the compiler to perform only a single access to a variable
  25  * (prohibits merging and refetching). The compiler is also forbidden to reorder
  26  * successive instances of CMM_ACCESS_ONCE(), but only when the compiler is aware of
  27  * particular ordering. Compiler ordering can be ensured, for example, by
  28  * putting two CMM_ACCESS_ONCE() in separate C statements.
  29  *
  30  * This macro does absolutely -nothing- to prevent the CPU from reordering,
  31  * merging, or refetching absolutely anything at any time.  Its main intended
  32  * use is to mediate communication between process-level code and irq/NMI
  33  * handlers, all running on the same CPU.
  34  */
  35 #define CMM_ACCESS_ONCE(x)      (*(__volatile__  __typeof__(x) *)&(x))
  36
  37 #ifndef caa_max
  38 #define caa_max(a,b) ((a)>(b)?(a):(b))
  39 #endif
  40
  41 #ifndef caa_min
  42 #define caa_min(a,b) ((a)<(b)?(a):(b))
  43 #endif
  44
  45 #if defined(__SIZEOF_LONG__)
  46 #define CAA_BITS_PER_LONG       (__SIZEOF_LONG__ * 8)
  47 #elif defined(_LP64)
  48 #define CAA_BITS_PER_LONG       64
  49 #else
  50 #define CAA_BITS_PER_LONG       32
  51 #endif
  52
  53 /*
  54  * caa_container_of - Get the address of an object containing a field.
  55  *
  56  * @ptr: pointer to the field.
  57  * @type: type of the object.
  58  * @member: name of the field within the object.
  59  */
  60 #define caa_container_of(ptr, type, member)                             \
  61         __extension__                                                   \
  62         ({                                                              \
  63                 const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
  64                 (type *)((char *)__ptr - offsetof(type, member));       \
  65         })
  66
  67 /*
  68  * caa_container_of_check_null - Get the address of an object containing a field.
  69  *
  70  * @ptr: pointer to the field.
  71  * @type: type of the object.
  72  * @member: name of the field within the object.
  73  *
  74  * Return the address of the object containing the field. Return NULL if
  75  * @ptr is NULL.
  76  */
  77 #define caa_container_of_check_null(ptr, type, member)                  \
  78         __extension__                                                   \
  79         ({                                                              \
  80                 const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
  81                 (__ptr) ? (type *)((char *)__ptr - offsetof(type, member)) : NULL; \
  82         })
  83
  84 #define CAA_BUILD_BUG_ON_ZERO(cond) (sizeof(struct { int:-!!(cond); }))
  85 #define CAA_BUILD_BUG_ON(cond) ((void)CAA_BUILD_BUG_ON_ZERO(cond))
  86
  87 /*
  88  * __rcu is an annotation that documents RCU pointer accesses that need
  89  * to be protected by a read-side critical section. Eventually, a static
  90  * checker will be able to use this annotation to detect incorrect RCU
  91  * usage.
  92  */
  93 #define __rcu
  94
  95 #ifdef __cplusplus
  96 #define URCU_FORCE_CAST(_type, arg)     (reinterpret_cast<std::remove_cv<_type>::type>(arg))
  97 #else
  98 #define URCU_FORCE_CAST(type, arg)      ((type) (arg))
  99 #endif
 100
 101 #define caa_is_signed_type(type)        ((type) -1 < (type) 0)
 102
 103 /*
 104  * Cast to unsigned long, sign-extending if @v is signed.
 105  * Note: casting to a larger type or to same type size keeps the sign of
 106  * the expression being cast (see C99 6.3.1.3).
 107  */
 108 #define caa_cast_long_keep_sign(v)      ((unsigned long) (v))
 109
 110 #if defined (__GNUC__) \
 111         && ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 5)    \
 112                 || __GNUC__ >= 5)
 113 #define CDS_DEPRECATED(msg)     \
 114         __attribute__((deprecated(msg)))
 115 #else
 116 #define CDS_DEPRECATED(msg)     \
 117         __attribute__((deprecated))
 118 #endif
 119
 120 #define CAA_ARRAY_SIZE(x)       (sizeof(x) / sizeof((x)[0]))
 121
 122 /*
 123  * URCU_GCC_VERSION is used to blacklist specific GCC versions with known
 124  * bugs, clang also defines these macros to an equivalent GCC version it
 125  * claims to support, so exclude it.
 126  */
 127 #if defined(__GNUC__) && !defined(__clang__)
 128 # define URCU_GCC_VERSION       (__GNUC__ * 10000 \
 129                                 + __GNUC_MINOR__ * 100 \
 130                                 + __GNUC_PATCHLEVEL__)
 131 #endif
 132
 133 #endif /* _URCU_COMPILER_H */