include/linux/compiler_attributes.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef __LINUX_COMPILER_ATTRIBUTES_H
0003 #define __LINUX_COMPILER_ATTRIBUTES_H
0004
0005 /*
0006  * The attributes in this file are unconditionally defined and they directly
0007  * map to compiler attribute(s), unless one of the compilers does not support
0008  * the attribute. In that case, __has_attribute is used to check for support
0009  * and the reason is stated in its comment ("Optional: ...").
0010  *
0011  * Any other "attributes" (i.e. those that depend on a configuration option,
0012  * on a compiler, on an architecture, on plugins, on other attributes...)
0013  * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
0014  * The intention is to keep this file as simple as possible, as well as
0015  * compiler- and version-agnostic (e.g. avoiding GCC_VERSION checks).
0016  *
0017  * This file is meant to be sorted (by actual attribute name,
0018  * not by #define identifier). Use the __attribute__((__name__)) syntax
0019  * (i.e. with underscores) to avoid future collisions with other macros.
0020  * Provide links to the documentation of each supported compiler, if it exists.
0021  */
0022
0023 /*
0024  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
0025  */
0026 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
0027
0028 /*
0029  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
0030  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
0031  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
0032  */
0033 #define __aligned(x)                    __attribute__((__aligned__(x)))
0034 #define __aligned_largest               __attribute__((__aligned__))
0035
0036 /*
0037  * Note: do not use this directly. Instead, use __alloc_size() since it is conditionally
0038  * available and includes other attributes.
0039  *
0040  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
0041  * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
0042  */
0043 #define __alloc_size__(x, ...)      __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
0044
0045 /*
0046  * Note: users of __always_inline currently do not write "inline" themselves,
0047  * which seems to be required by gcc to apply the attribute according
0048  * to its docs (and also "warning: always_inline function might not be
0049  * inlinable [-Wattributes]" is emitted).
0050  *
0051  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
0052  * clang: mentioned
0053  */
0054 #define __always_inline                 inline __attribute__((__always_inline__))
0055
0056 /*
0057  * The second argument is optional (default 0), so we use a variadic macro
0058  * to make the shorthand.
0059  *
0060  * Beware: Do not apply this to functions which may return
0061  * ERR_PTRs. Also, it is probably unwise to apply it to functions
0062  * returning extra information in the low bits (but in that case the
0063  * compiler should see some alignment anyway, when the return value is
0064  * massaged by 'flags = ptr & 3; ptr &= ~3;').
0065  *
0066  * Optional: not supported by icc
0067  *
0068  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
0069  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
0070  */
0071 #if __has_attribute(__assume_aligned__)
0072 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
0073 #else
0074 # define __assume_aligned(a, ...)
0075 #endif
0076
0077 /*
0078  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
0079  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
0080  */
0081 #define __cold                          __attribute__((__cold__))
0082
0083 /*
0084  * Note the long name.
0085  *
0086  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
0087  */
0088 #define __attribute_const__             __attribute__((__const__))
0089
0090 /*
0091  * Optional: only supported since gcc >= 9
0092  * Optional: not supported by clang
0093  * Optional: not supported by icc
0094  *
0095  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
0096  */
0097 #if __has_attribute(__copy__)
0098 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
0099 #else
0100 # define __copy(symbol)
0101 #endif
0102
0103 /*
0104  * Optional: not supported by gcc
0105  * Optional: only supported since clang >= 14.0
0106  * Optional: not supported by icc
0107  *
0108  * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
0109  */
0110 #if __has_attribute(__diagnose_as_builtin__)
0111 # define __diagnose_as(builtin...)  __attribute__((__diagnose_as_builtin__(builtin)))
0112 #else
0113 # define __diagnose_as(builtin...)
0114 #endif
0115
0116 /*
0117  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
0118  * attribute warnings entirely and for good") for more information.
0119  *
0120  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
0121  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
0122  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
0123  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
0124  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
0125  */
0126 #define __deprecated
0127
0128 /*
0129  * Optional: not supported by clang
0130  * Optional: not supported by icc
0131  *
0132  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
0133  */
0134 #if __has_attribute(__designated_init__)
0135 # define __designated_init              __attribute__((__designated_init__))
0136 #else
0137 # define __designated_init
0138 #endif
0139
0140 /*
0141  * Optional: only supported since clang >= 14.0
0142  *
0143  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
0144  */
0145 #if __has_attribute(__error__)
0146 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
0147 #else
0148 # define __compiletime_error(msg)
0149 #endif
0150
0151 /*
0152  * Optional: not supported by clang
0153  *
0154  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
0155  */
0156 #if __has_attribute(__externally_visible__)
0157 # define __visible                      __attribute__((__externally_visible__))
0158 #else
0159 # define __visible
0160 #endif
0161
0162 /*
0163  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
0164  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
0165  */
0166 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
0167 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
0168
0169 /*
0170  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
0171  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
0172  */
0173 #define __gnu_inline                    __attribute__((__gnu_inline__))
0174
0175 /*
0176  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
0177  * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
0178  */
0179 #define __malloc                        __attribute__((__malloc__))
0180
0181 /*
0182  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
0183  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
0184  */
0185 #define __mode(x)                       __attribute__((__mode__(x)))
0186
0187 /*
0188  * Optional: only supported since gcc >= 7
0189  *
0190  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
0191  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
0192  */
0193 #if __has_attribute(__no_caller_saved_registers__)
0194 # define __no_caller_saved_registers    __attribute__((__no_caller_saved_registers__))
0195 #else
0196 # define __no_caller_saved_registers
0197 #endif
0198
0199 /*
0200  * Optional: not supported by clang
0201  *
0202  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
0203  */
0204 #if __has_attribute(__noclone__)
0205 # define __noclone                      __attribute__((__noclone__))
0206 #else
0207 # define __noclone
0208 #endif
0209
0210 /*
0211  * Add the pseudo keyword 'fallthrough' so case statement blocks
0212  * must end with any of these keywords:
0213  *   break;
0214  *   fallthrough;
0215  *   continue;
0216  *   goto <label>;
0217  *   return [expression];
0218  *
0219  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
0220  */
0221 #if __has_attribute(__fallthrough__)
0222 # define fallthrough                    __attribute__((__fallthrough__))
0223 #else
0224 # define fallthrough                    do {} while (0)  /* fallthrough */
0225 #endif
0226
0227 /*
0228  * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
0229  * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
0230  */
0231 # define __flatten          __attribute__((flatten))
0232
0233 /*
0234  * Note the missing underscores.
0235  *
0236  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
0237  * clang: mentioned
0238  */
0239 #define   noinline                      __attribute__((__noinline__))
0240
0241 /*
0242  * Optional: only supported since gcc >= 8
0243  * Optional: not supported by clang
0244  * Optional: not supported by icc
0245  *
0246  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
0247  */
0248 #if __has_attribute(__nonstring__)
0249 # define __nonstring                    __attribute__((__nonstring__))
0250 #else
0251 # define __nonstring
0252 #endif
0253
0254 /*
0255  * Optional: only supported since GCC >= 7.1, clang >= 13.0.
0256  *
0257  *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
0258  *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
0259  */
0260 #if __has_attribute(__no_profile_instrument_function__)
0261 # define __no_profile                  __attribute__((__no_profile_instrument_function__))
0262 #else
0263 # define __no_profile
0264 #endif
0265
0266 /*
0267  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
0268  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
0269  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
0270  */
0271 #define __noreturn                      __attribute__((__noreturn__))
0272
0273 /*
0274  * Optional: not supported by gcc.
0275  * Optional: not supported by icc.
0276  *
0277  * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
0278  */
0279 #if __has_attribute(__overloadable__)
0280 # define __overloadable         __attribute__((__overloadable__))
0281 #else
0282 # define __overloadable
0283 #endif
0284
0285 /*
0286  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
0287  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
0288  */
0289 #define __packed                        __attribute__((__packed__))
0290
0291 /*
0292  * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
0293  *
0294  * Optional: not supported by gcc.
0295  * Optional: not supported by icc.
0296  *
0297  * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
0298  */
0299 #if __has_attribute(__pass_object_size__)
0300 # define __pass_object_size(type)   __attribute__((__pass_object_size__(type)))
0301 #else
0302 # define __pass_object_size(type)
0303 #endif
0304
0305 /*
0306  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
0307  */
0308 #define __pure                          __attribute__((__pure__))
0309
0310 /*
0311  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
0312  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
0313  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
0314  */
0315 #define __section(section)              __attribute__((__section__(section)))
0316
0317 /*
0318  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
0319  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
0320  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
0321  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
0322  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
0323  */
0324 #define __always_unused                 __attribute__((__unused__))
0325 #define __maybe_unused                  __attribute__((__unused__))
0326
0327 /*
0328  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
0329  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
0330  */
0331 #define __used                          __attribute__((__used__))
0332
0333 /*
0334  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
0335  * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
0336  */
0337 #define __must_check                    __attribute__((__warn_unused_result__))
0338
0339 /*
0340  * Optional: only supported since clang >= 14.0
0341  *
0342  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
0343  */
0344 #if __has_attribute(__warning__)
0345 # define __compiletime_warning(msg)     __attribute__((__warning__(msg)))
0346 #else
0347 # define __compiletime_warning(msg)
0348 #endif
0349
0350 /*
0351  * Optional: only supported since clang >= 14.0
0352  *
0353  * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
0354  *
0355  * disable_sanitizer_instrumentation is not always similar to
0356  * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
0357  * insert code into functions to prevent false positives. Unlike that,
0358  * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
0359  * functions with the attribute.
0360  */
0361 #if __has_attribute(disable_sanitizer_instrumentation)
0362 # define __disable_sanitizer_instrumentation \
0363      __attribute__((disable_sanitizer_instrumentation))
0364 #else
0365 # define __disable_sanitizer_instrumentation
0366 #endif
0367
0368 /*
0369  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
0370  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
0371  */
0372 #define __weak                          __attribute__((__weak__))
0373
0374 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */