4 * Compiler-specific definitions. Currently, only GCC and clang are supported.
6 * Copyright 2022 Eric Biggers
8 * Permission is hereby granted, free of charge, to any person
9 * obtaining a copy of this software and associated documentation
10 * files (the "Software"), to deal in the Software without
11 * restriction, including without limitation the rights to use,
12 * copy, modify, merge, publish, distribute, sublicense, and/or sell
13 * copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
22 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
24 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
25 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
27 * OTHER DEALINGS IN THE SOFTWARE.
30 #ifndef _WIMLIB_COMPILER_H
31 #define _WIMLIB_COMPILER_H
33 /* Is the compiler GCC of the specified version or later? This always returns
34 * false for clang, since clang is "frozen" at GNUC 4.2. The __has_*
35 * feature-test macros should be used to detect clang functionality instead. */
36 #define GCC_PREREQ(major, minor) \
37 (!defined(__clang__) && !defined(__INTEL_COMPILER) && \
38 (__GNUC__ > major || \
39 (__GNUC__ == major && __GNUC_MINOR__ >= minor)))
41 /* Feature-test macros defined by recent versions of clang. */
42 #ifndef __has_attribute
43 # define __has_attribute(attribute) 0
46 # define __has_feature(feature) 0
49 # define __has_builtin(builtin) 0
52 /* Declare that the annotated function should be exported from the shared
53 * library (or DLL). */
55 # define WIMLIBAPI __declspec(dllexport)
57 # define WIMLIBAPI __attribute__((visibility("default")))
60 /* Declare that the annotated function should always be inlined. This might be
61 * desirable in highly tuned code, e.g. compression codecs. */
62 #define forceinline inline __attribute__((always_inline))
64 /* Declare that the annotated function should *not* be inlined. */
65 #define noinline __attribute__((noinline))
67 /* Functionally the same as 'noinline', but documents that the reason for not
68 * inlining is to prevent the annotated function from being inlined into a
69 * recursive function, thereby increasing its stack usage. */
70 #define noinline_for_stack noinline
72 /* Hint that the expression is usually true. */
73 #define likely(expr) __builtin_expect(!!(expr), 1)
75 /* Hint that the expression is usually false. */
76 #define unlikely(expr) __builtin_expect(!!(expr), 0)
78 /* Prefetch into L1 cache for read. */
79 #define prefetchr(addr) __builtin_prefetch((addr), 0)
81 /* Prefetch into L1 cache for write. */
82 #define prefetchw(addr) __builtin_prefetch((addr), 1)
84 /* Declare that the members of the annotated struct are tightly packed, and the
85 * struct itself may be misaligned. */
86 #define _packed_attribute __attribute__((packed))
88 /* Declare that the annotated variable, or variables of the annotated type, are
89 * to be aligned on n-byte boundaries. */
90 #define _aligned_attribute(n) __attribute__((aligned(n)))
92 /* Declare that pointers to the annotated type may alias other pointers. */
93 #define _may_alias_attribute __attribute__((may_alias))
95 /* Hint that the annotated function is rarely called. */
96 #if GCC_PREREQ(4, 4) || __has_attribute(cold)
97 # define _cold_attribute __attribute__((cold))
99 # define _cold_attribute
102 /* Hint that the annotated function takes a printf()-like format string and
103 * arguments. This is currently disabled on Windows because MinGW does not
104 * support this attribute on functions taking wide-character strings. */
106 # define _format_attribute(type, format_str, format_start)
108 # define _format_attribute(type, format_str, format_start) \
109 __attribute__((format(type, format_str, format_start)))
112 /* Hint that the annotated function is intentionally not used. This might be
113 * the case if the function contains only static assertions. */
114 #define _unused_attribute __attribute__((unused))
116 /* Endianness definitions. Either CPU_IS_BIG_ENDIAN() or CPU_IS_LITTLE_ENDIAN()
117 * evaluates to 1. The other evaluates to 0. Note that newer gcc supports
118 * __BYTE_ORDER__ for easily determining the endianness; older gcc doesn't. In
119 * the latter case we fall back to a configure-time check. */
120 #ifdef __BYTE_ORDER__
121 # define CPU_IS_BIG_ENDIAN() (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
122 #elif defined(HAVE_CONFIG_H)
124 # ifdef WORDS_BIGENDIAN
125 # define CPU_IS_BIG_ENDIAN() 1
127 # define CPU_IS_BIG_ENDIAN() 0
130 #define CPU_IS_LITTLE_ENDIAN() (!CPU_IS_BIG_ENDIAN())
132 /* UNALIGNED_ACCESS_IS_FAST should be defined to 1 if unaligned memory accesses
133 * can be performed efficiently on the target platform. */
134 #if defined(__x86_64__) || defined(__i386__) || defined(__ARM_FEATURE_UNALIGNED)
135 # define UNALIGNED_ACCESS_IS_FAST 1
137 # define UNALIGNED_ACCESS_IS_FAST 0
140 /* Get the type of the specified expression. */
141 #define typeof __typeof__
143 /* Get the minimum of two variables, without multiple evaluation. */
145 #define min(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
146 (_a < _b) ? _a : _b; })
148 #define MIN(a, b) min((a), (b))
150 /* Get the maximum of two variables, without multiple evaluation. */
152 #define max(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
153 (_a > _b) ? _a : _b; })
155 #define MAX(a, b) max((a), (b))
157 /* Swap the values of two variables, without multiple evaluation. */
159 # define swap(a, b) ({ typeof(a) _a = (a); (a) = (b); (b) = _a; })
161 #define SWAP(a, b) swap((a), (b))
163 /* (Optional) Efficiently swap the bytes of a 16-bit integer. */
164 #if GCC_PREREQ(4, 8) || __has_builtin(__builtin_bswap16)
165 # define compiler_bswap16 __builtin_bswap16
168 /* (Optional) Efficiently swap the bytes of a 32-bit integer. */
169 #if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap32)
170 # define compiler_bswap32 __builtin_bswap32
173 /* (Optional) Efficiently swap the bytes of a 64-bit integer. */
174 #if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap64)
175 # define compiler_bswap64 __builtin_bswap64
178 /* (Optional) Find Last Set bit and Find First Set bit macros. */
179 #define compiler_bsr32(n) (31 - __builtin_clz(n))
180 #define compiler_bsr64(n) (63 - __builtin_clzll(n))
181 #define compiler_bsf32(n) __builtin_ctz(n)
182 #define compiler_bsf64(n) __builtin_ctzll(n)
184 /* Optional definitions for checking with 'sparse'. */
186 # define _bitwise_attr __attribute__((bitwise))
187 # define _force_attr __attribute__((force))
189 # define _bitwise_attr
193 /* STATIC_ASSERT() - verify the truth of an expression at compilation time. */
195 # define STATIC_ASSERT(expr)
196 #elif __STDC_VERSION__ >= 201112L
197 # define STATIC_ASSERT(expr) _Static_assert((expr), "")
199 # define STATIC_ASSERT(expr) ((void)sizeof(char[1 - 2 * !(expr)]))
202 /* STATIC_ASSERT_ZERO() - verify the truth of an expression at compilation time
203 * and also produce a result of value '0' to be used in constant expressions */
204 #define STATIC_ASSERT_ZERO(expr) ((int)sizeof(char[-!(expr)]))
206 #define CONCAT_IMPL(s1, s2) s1##s2
208 /* CONCAT() - concatenate two tokens at preprocessing time. */
209 #define CONCAT(s1, s2) CONCAT_IMPL(s1, s2)
211 #endif /* _WIMLIB_COMPILER_H */