1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_COMPILER_ATTRIBUTES_H
3 #define __LINUX_COMPILER_ATTRIBUTES_H
4 
5 /*
6  * The attributes in this file are unconditionally defined and they directly
7  * map to compiler attribute(s), unless one of the compilers does not support
8  * the attribute. In that case, __has_attribute is used to check for support
9  * and the reason is stated in its comment ("Optional: ...").
10  *
11  * Any other "attributes" (i.e. those that depend on a configuration option,
12  * on a compiler, on an architecture, on plugins, on other attributes...)
13  * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
14  * The intention is to keep this file as simple as possible, as well as
15  * compiler- and version-agnostic (e.g. avoiding GCC_VERSION checks).
16  *
17  * This file is meant to be sorted (by actual attribute name,
18  * not by #define identifier). Use the __attribute__((__name__)) syntax
19  * (i.e. with underscores) to avoid future collisions with other macros.
20  * Provide links to the documentation of each supported compiler, if it exists.
21  */
22 
23 /*
24  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
25  */
26 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
27 
28 /*
29  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
30  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
31  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
32  */
33 #define __aligned(x)                    __attribute__((__aligned__(x)))
34 #define __aligned_largest               __attribute__((__aligned__))
35 
36 /*
37  * Note: do not use this directly. Instead, use __alloc_size() since it is conditionally
38  * available and includes other attributes. For GCC < 9.1, __alloc_size__ gets undefined
39  * in compiler-gcc.h, due to misbehaviors.
40  *
41  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
42  * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
43  */
44 #define __alloc_size__(x, ...)		__attribute__((__alloc_size__(x, ## __VA_ARGS__)))
45 
46 /*
47  * Note: users of __always_inline currently do not write "inline" themselves,
48  * which seems to be required by gcc to apply the attribute according
49  * to its docs (and also "warning: always_inline function might not be
50  * inlinable [-Wattributes]" is emitted).
51  *
52  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
53  * clang: mentioned
54  */
55 #define __always_inline                 inline __attribute__((__always_inline__))
56 
57 /*
58  * The second argument is optional (default 0), so we use a variadic macro
59  * to make the shorthand.
60  *
61  * Beware: Do not apply this to functions which may return
62  * ERR_PTRs. Also, it is probably unwise to apply it to functions
63  * returning extra information in the low bits (but in that case the
64  * compiler should see some alignment anyway, when the return value is
65  * massaged by 'flags = ptr & 3; ptr &= ~3;').
66  *
67  * Optional: not supported by icc
68  *
69  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
70  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
71  */
72 #if __has_attribute(__assume_aligned__)
73 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
74 #else
75 # define __assume_aligned(a, ...)
76 #endif
77 
78 /*
79  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
80  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
81  */
82 #define __cold                          __attribute__((__cold__))
83 
84 /*
85  * Note the long name.
86  *
87  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
88  */
89 #define __attribute_const__             __attribute__((__const__))
90 
91 /*
92  * Optional: only supported since gcc >= 9
93  * Optional: not supported by clang
94  * Optional: not supported by icc
95  *
96  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
97  */
98 #if __has_attribute(__copy__)
99 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
100 #else
101 # define __copy(symbol)
102 #endif
103 
104 /*
105  * Optional: not supported by gcc
106  * Optional: only supported since clang >= 14.0
107  * Optional: not supported by icc
108  *
109  * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
110  */
111 #if __has_attribute(__diagnose_as_builtin__)
112 # define __diagnose_as(builtin...)	__attribute__((__diagnose_as_builtin__(builtin)))
113 #else
114 # define __diagnose_as(builtin...)
115 #endif
116 
117 /*
118  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
119  * attribute warnings entirely and for good") for more information.
120  *
121  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
122  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
123  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
124  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
125  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
126  */
127 #define __deprecated
128 
129 /*
130  * Optional: not supported by clang
131  * Optional: not supported by icc
132  *
133  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
134  */
135 #if __has_attribute(__designated_init__)
136 # define __designated_init              __attribute__((__designated_init__))
137 #else
138 # define __designated_init
139 #endif
140 
141 /*
142  * Optional: only supported since clang >= 14.0
143  *
144  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
145  */
146 #if __has_attribute(__error__)
147 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
148 #else
149 # define __compiletime_error(msg)
150 #endif
151 
152 /*
153  * Optional: not supported by clang
154  *
155  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
156  */
157 #if __has_attribute(__externally_visible__)
158 # define __visible                      __attribute__((__externally_visible__))
159 #else
160 # define __visible
161 #endif
162 
163 /*
164  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
165  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
166  */
167 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
168 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
169 
170 /*
171  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
172  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
173  */
174 #define __gnu_inline                    __attribute__((__gnu_inline__))
175 
176 /*
177  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
178  * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
179  */
180 #define __malloc                        __attribute__((__malloc__))
181 
182 /*
183  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
184  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
185  */
186 #define __mode(x)                       __attribute__((__mode__(x)))
187 
188 /*
189  * Optional: only supported since gcc >= 7
190  *
191  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
192  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
193  */
194 #if __has_attribute(__no_caller_saved_registers__)
195 # define __no_caller_saved_registers	__attribute__((__no_caller_saved_registers__))
196 #else
197 # define __no_caller_saved_registers
198 #endif
199 
200 /*
201  * Optional: not supported by clang
202  *
203  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
204  */
205 #if __has_attribute(__noclone__)
206 # define __noclone                      __attribute__((__noclone__))
207 #else
208 # define __noclone
209 #endif
210 
211 /*
212  * Add the pseudo keyword 'fallthrough' so case statement blocks
213  * must end with any of these keywords:
214  *   break;
215  *   fallthrough;
216  *   continue;
217  *   goto <label>;
218  *   return [expression];
219  *
220  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
221  */
222 #if __has_attribute(__fallthrough__)
223 # define fallthrough                    __attribute__((__fallthrough__))
224 #else
225 # define fallthrough                    do {} while (0)  /* fallthrough */
226 #endif
227 
228 /*
229  * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
230  * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
231  */
232 # define __flatten			__attribute__((flatten))
233 
234 /*
235  * Note the missing underscores.
236  *
237  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
238  * clang: mentioned
239  */
240 #define   noinline                      __attribute__((__noinline__))
241 
242 /*
243  * Optional: only supported since gcc >= 8
244  * Optional: not supported by clang
245  * Optional: not supported by icc
246  *
247  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
248  */
249 #if __has_attribute(__nonstring__)
250 # define __nonstring                    __attribute__((__nonstring__))
251 #else
252 # define __nonstring
253 #endif
254 
255 /*
256  * Optional: only supported since GCC >= 7.1, clang >= 13.0.
257  *
258  *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
259  *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
260  */
261 #if __has_attribute(__no_profile_instrument_function__)
262 # define __no_profile                  __attribute__((__no_profile_instrument_function__))
263 #else
264 # define __no_profile
265 #endif
266 
267 /*
268  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
269  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
270  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
271  */
272 #define __noreturn                      __attribute__((__noreturn__))
273 
274 /*
275  * Optional: not supported by gcc.
276  * Optional: not supported by icc.
277  *
278  * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
279  */
280 #if __has_attribute(__overloadable__)
281 # define __overloadable			__attribute__((__overloadable__))
282 #else
283 # define __overloadable
284 #endif
285 
286 /*
287  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
288  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
289  */
290 #define __packed                        __attribute__((__packed__))
291 
292 /*
293  * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
294  *
295  * Optional: not supported by gcc.
296  * Optional: not supported by icc.
297  *
298  * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
299  */
300 #if __has_attribute(__pass_object_size__)
301 # define __pass_object_size(type)	__attribute__((__pass_object_size__(type)))
302 #else
303 # define __pass_object_size(type)
304 #endif
305 
306 /*
307  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
308  */
309 #define __pure                          __attribute__((__pure__))
310 
311 /*
312  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
313  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
314  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
315  */
316 #define __section(section)              __attribute__((__section__(section)))
317 
318 /*
319  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
320  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
321  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
322  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
323  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
324  */
325 #define __always_unused                 __attribute__((__unused__))
326 #define __maybe_unused                  __attribute__((__unused__))
327 
328 /*
329  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
330  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
331  */
332 #define __used                          __attribute__((__used__))
333 
334 /*
335  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
336  * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
337  */
338 #define __must_check                    __attribute__((__warn_unused_result__))
339 
340 /*
341  * Optional: only supported since clang >= 14.0
342  *
343  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
344  */
345 #if __has_attribute(__warning__)
346 # define __compiletime_warning(msg)     __attribute__((__warning__(msg)))
347 #else
348 # define __compiletime_warning(msg)
349 #endif
350 
351 /*
352  * Optional: only supported since clang >= 14.0
353  *
354  * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
355  *
356  * disable_sanitizer_instrumentation is not always similar to
357  * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
358  * insert code into functions to prevent false positives. Unlike that,
359  * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
360  * functions with the attribute.
361  */
362 #if __has_attribute(disable_sanitizer_instrumentation)
363 # define __disable_sanitizer_instrumentation \
364 	 __attribute__((disable_sanitizer_instrumentation))
365 #else
366 # define __disable_sanitizer_instrumentation
367 #endif
368 
369 /*
370  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
371  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
372  */
373 #define __weak                          __attribute__((__weak__))
374 
375 /*
376  * Used by functions that use '__builtin_return_address'. These function
377  * don't want to be splited or made inline, which can make
378  * the '__builtin_return_address' get unexpected address.
379  */
380 #define __fix_address noinline __noclone
381 
382 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */
383