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 #include <urcu/config.h>
  19
  20 #define caa_likely(x)   __builtin_expect(!!(x), 1)
  21 #define caa_unlikely(x) __builtin_expect(!!(x), 0)
  22
  23 #ifdef CONFIG_RCU_USE_ATOMIC_BUILTINS
  24 #  define cmm_barrier() __atomic_signal_fence(__ATOMIC_SEQ_CST)
  25 #else
  26 #  define cmm_barrier() __asm__ __volatile__ ("" : : : "memory")
  27 #endif
  28
  29 /*
  30  * Instruct the compiler to perform only a single access to a variable
  31  * (prohibits merging and refetching). The compiler is also forbidden to reorder
  32  * successive instances of CMM_ACCESS_ONCE(), but only when the compiler is aware of
  33  * particular ordering. Compiler ordering can be ensured, for example, by
  34  * putting two CMM_ACCESS_ONCE() in separate C statements.
  35  *
  36  * This macro does absolutely -nothing- to prevent the CPU from reordering,
  37  * merging, or refetching absolutely anything at any time.  Its main intended
  38  * use is to mediate communication between process-level code and irq/NMI
  39  * handlers, all running on the same CPU.
  40  */
  41 #define CMM_ACCESS_ONCE(x)      (*(__volatile__  __typeof__(x) *)&(x))
  42
  43 #ifndef caa_max
  44 #define caa_max(a,b) ((a)>(b)?(a):(b))
  45 #endif
  46
  47 #ifndef caa_min
  48 #define caa_min(a,b) ((a)<(b)?(a):(b))
  49 #endif
  50
  51 #if defined(__SIZEOF_LONG__)
  52 #define CAA_BITS_PER_LONG       (__SIZEOF_LONG__ * 8)
  53 #elif defined(_LP64)
  54 #define CAA_BITS_PER_LONG       64
  55 #else
  56 #define CAA_BITS_PER_LONG       32
  57 #endif
  58
  59 /*
  60  * caa_container_of - Get the address of an object containing a field.
  61  *
  62  * @ptr: pointer to the field.
  63  * @type: type of the object.
  64  * @member: name of the field within the object.
  65  */
  66 #define caa_container_of(ptr, type, member)                             \
  67         __extension__                                                   \
  68         ({                                                              \
  69                 const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
  70                 (type *)((char *)__ptr - offsetof(type, member));       \
  71         })
  72
  73 /*
  74  * caa_container_of_check_null - Get the address of an object containing a field.
  75  *
  76  * @ptr: pointer to the field.
  77  * @type: type of the object.
  78  * @member: name of the field within the object.
  79  *
  80  * Return the address of the object containing the field. Return NULL if
  81  * @ptr is NULL.
  82  */
  83 #define caa_container_of_check_null(ptr, type, member)                  \
  84         __extension__                                                   \
  85         ({                                                              \
  86                 const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
  87                 (__ptr) ? (type *)((char *)__ptr - offsetof(type, member)) : NULL; \
  88         })
  89
  90 #define CAA_BUILD_BUG_ON_ZERO(cond) (sizeof(struct { int:-!!(cond); }))
  91 #define CAA_BUILD_BUG_ON(cond) ((void)CAA_BUILD_BUG_ON_ZERO(cond))
  92
  93 /*
  94  * __rcu is an annotation that documents RCU pointer accesses that need
  95  * to be protected by a read-side critical section. Eventually, a static
  96  * checker will be able to use this annotation to detect incorrect RCU
  97  * usage.
  98  */
  99 #define __rcu
 100
 101 #ifdef __cplusplus
 102 #define URCU_FORCE_CAST(_type, arg)     (reinterpret_cast<std::remove_cv<_type>::type>(arg))
 103 #else
 104 #define URCU_FORCE_CAST(type, arg)      ((type) (arg))
 105 #endif
 106
 107 #define caa_is_signed_type(type)        ((type) -1 < (type) 0)
 108
 109 /*
 110  * Cast to unsigned long, sign-extending if @v is signed.
 111  * Note: casting to a larger type or to same type size keeps the sign of
 112  * the expression being cast (see C99 6.3.1.3).
 113  */
 114 #define caa_cast_long_keep_sign(v)      ((unsigned long) (v))
 115
 116 #if defined (__GNUC__) \
 117         && ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 5)    \
 118                 || __GNUC__ >= 5)
 119 #define CDS_DEPRECATED(msg)     \
 120         __attribute__((deprecated(msg)))
 121 #else
 122 #define CDS_DEPRECATED(msg)     \
 123         __attribute__((deprecated))
 124 #endif
 125
 126 #define CAA_ARRAY_SIZE(x)       (sizeof(x) / sizeof((x)[0]))
 127
 128 /*
 129  * URCU_GCC_VERSION is used to blacklist specific GCC versions with known
 130  * bugs, clang also defines these macros to an equivalent GCC version it
 131  * claims to support, so exclude it.
 132  */
 133 #if defined(__GNUC__) && !defined(__clang__)
 134 # define URCU_GCC_VERSION       (__GNUC__ * 10000 \
 135                                 + __GNUC_MINOR__ * 100 \
 136                                 + __GNUC_PATCHLEVEL__)
 137 #endif
 138
 139 #ifdef __cplusplus
 140 #define caa_unqual_scalar_typeof(x)                                     \
 141         std::remove_cv<std::remove_reference<decltype(x)>::type>::type
 142 #else
 143 #define caa_scalar_type_to_expr(type)                                   \
 144         unsigned type: (unsigned type)0,                                \
 145         signed type: (signed type)0
 146
 147 /*
 148  * Use C11 _Generic to express unqualified type from expression. This removes
 149  * volatile qualifier from expression type.
 150  */
 151 #define caa_unqual_scalar_typeof(x)                                     \
 152         __typeof__(                                                     \
 153                 _Generic((x),                                           \
 154                         char: (char)0,                                  \
 155                         caa_scalar_type_to_expr(char),                  \
 156                         caa_scalar_type_to_expr(short),         \
 157                         caa_scalar_type_to_expr(int),                   \
 158                         caa_scalar_type_to_expr(long),                  \
 159                         caa_scalar_type_to_expr(long long),             \
 160                         default: (x)                                    \
 161                 )                                                       \
 162         )
 163 #endif
 164
 165 /*
 166  * Allow user to manually define CMM_SANITIZE_THREAD if their toolchain is not
 167  * supported by this check.
 168  */
 169 #ifndef CMM_SANITIZE_THREAD
 170 # if defined(__GNUC__) && defined(__SANITIZE_THREAD__)
 171 #  define CMM_SANITIZE_THREAD
 172 # elif defined(__clang__) && defined(__has_feature)
 173 #  if __has_feature(thread_sanitizer)
 174 #   define CMM_SANITIZE_THREAD
 175 #  endif
 176 # endif
 177 #endif  /* !CMM_SANITIZE_THREAD */
 178
 179 /*
 180  * Helper to add the volatile qualifier to a pointer.
 181  */
 182 #if defined __cplusplus
 183 template <typename T>
 184 volatile T cmm_cast_volatile(T t)
 185 {
 186     return static_cast<volatile T>(t);
 187 }
 188 #else
 189 #  define cmm_cast_volatile(ptr)                        \
 190         __extension__                                   \
 191         ({                                              \
 192                 (volatile __typeof__(ptr))(ptr);        \
 193         })
 194 #endif
 195
 196 /*
 197  * Compile time assertion.
 198  * - predicate: boolean expression to evaluate,
 199  * - msg: string to print to the user on failure when `static_assert()` is
 200  *   supported,
 201  * - c_identifier_msg: message to be included in the typedef to emulate a
 202  *   static assertion. This parameter must be a valid C identifier as it will
 203  *   be used as a typedef name.
 204  */
 205 #ifdef __cplusplus
 206 #define urcu_static_assert(predicate, msg, c_identifier_msg)  \
 207         static_assert(predicate, msg)
 208 #elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
 209 #define urcu_static_assert(predicate, msg, c_identifier_msg)  \
 210         _Static_assert(predicate, msg)
 211 #else
 212 /*
 213  * Evaluates the predicate and emit a compilation error on failure.
 214  *
 215  * If the predicate evaluates to true, this macro emits a function
 216  * prototype with an argument type which is an array of size 0.
 217  *
 218  * If the predicate evaluates to false, this macro emits a function
 219  * prototype with an argument type which is an array of negative size
 220  * which is invalid in C and forces a compiler error. The
 221  * c_identifier_msg parameter is used as the argument identifier so it
 222  * is printed to the user when the error is reported.
 223  */
 224 #define urcu_static_assert(predicate, msg, c_identifier_msg)  \
 225         void urcu_static_assert_proto(char c_identifier_msg[2*!!(predicate)-1])
 226 #endif
 227
 228 #endif /* _URCU_COMPILER_H */