4 * Compiler-specific definitions. Currently, only GCC and clang are supported.
6 * The following copying information applies to this specific source code file:
8 * Written in 2013-2016 by Eric Biggers <ebiggers3@gmail.com>
10 * To the extent possible under law, the author(s) have dedicated all copyright
11 * and related and neighboring rights to this software to the public domain
12 * worldwide via the Creative Commons Zero 1.0 Universal Public Domain
13 * Dedication (the "CC0").
15 * This software is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 * FOR A PARTICULAR PURPOSE. See the CC0 for more details.
19 * You should have received a copy of the CC0 along with this software; if not
20 * see <http://creativecommons.org/publicdomain/zero/1.0/>.
23 #ifndef _WIMLIB_COMPILER_H
24 #define _WIMLIB_COMPILER_H
26 /* Is the compiler GCC of the specified version or later? This always returns
27 * false for clang, since clang is "frozen" at GNUC 4.2. The __has_*
28 * feature-test macros should be used to detect clang functionality instead. */
29 #define GCC_PREREQ(major, minor) \
30 (!defined(__clang__) && !defined(__INTEL_COMPILER) && \
31 (__GNUC__ > major || \
32 (__GNUC__ == major && __GNUC_MINOR__ >= minor)))
34 /* Feature-test macros defined by recent versions of clang. */
35 #ifndef __has_attribute
36 # define __has_attribute(attribute) 0
39 # define __has_feature(feature) 0
42 # define __has_builtin(builtin) 0
45 /* Declare that the annotated function should be exported from the shared
46 * library (or DLL). */
48 # define WIMLIBAPI __declspec(dllexport)
50 # define WIMLIBAPI __attribute__((visibility("default")))
53 /* Declare that the annotated function should always be inlined. This might be
54 * desirable in highly tuned code, e.g. compression codecs. */
55 #define forceinline inline __attribute__((always_inline))
57 /* Declare that the annotated function should *not* be inlined. */
58 #define noinline __attribute__((noinline))
60 /* Functionally the same as 'noinline', but documents that the reason for not
61 * inlining is to prevent the annotated function from being inlined into a
62 * recursive function, thereby increasing its stack usage. */
63 #define noinline_for_stack noinline
65 /* Hint that the expression is usually true. */
66 #define likely(expr) __builtin_expect(!!(expr), 1)
68 /* Hint that the expression is usually false. */
69 #define unlikely(expr) __builtin_expect(!!(expr), 0)
71 /* Prefetch into L1 cache for read. */
72 #define prefetchr(addr) __builtin_prefetch((addr), 0)
74 /* Prefetch into L1 cache for write. */
75 #define prefetchw(addr) __builtin_prefetch((addr), 1)
77 /* Declare that the members of the annotated struct are tightly packed, and the
78 * struct itself may be misaligned. */
79 #define _packed_attribute __attribute__((packed))
81 /* Declare that the annotated variable, or variables of the annotated type, are
82 * to be aligned on n-byte boundaries. */
83 #define _aligned_attribute(n) __attribute__((aligned(n)))
85 /* Declare that pointers to the annotated type may alias other pointers. */
86 #define _may_alias_attribute __attribute__((may_alias))
88 /* Hint that the annotated function is rarely called. */
89 #if GCC_PREREQ(4, 4) || __has_attribute(cold)
90 # define _cold_attribute __attribute__((cold))
92 # define _cold_attribute
95 /* Hint that the annotated function is malloc-like: any non-null pointer it
96 * returns will not alias any pointer previously in use by the program. */
97 #define _malloc_attribute __attribute__((malloc))
99 /* Hint that the annotated function takes a printf()-like format string and
100 * arguments. This is currently disabled on Windows because MinGW does not
101 * support this attribute on functions taking wide-character strings. */
103 # define _format_attribute(type, format_str, format_start)
105 # define _format_attribute(type, format_str, format_start) \
106 __attribute__((format(type, format_str, format_start)))
109 /* Hint that the annotated function is intentionally not used. This might be
110 * the case if the function contains only static assertions. */
111 #define _unused_attribute __attribute__((unused))
113 /* Endianness definitions. Either CPU_IS_BIG_ENDIAN or CPU_IS_LITTLE_ENDIAN is
114 * set to 1. The other is set to 0. Note that newer gcc supports
115 * __BYTE_ORDER__ for easily determining the endianness; older gcc doesn't. In
116 * the latter case we fall back to a configure-time check. */
117 #ifdef __BYTE_ORDER__
118 # define CPU_IS_BIG_ENDIAN (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
119 #elif defined(HAVE_CONFIG_H)
121 # ifdef WORDS_BIGENDIAN
122 # define CPU_IS_BIG_ENDIAN 1
124 # define CPU_IS_BIG_ENDIAN 0
127 #define CPU_IS_LITTLE_ENDIAN (!CPU_IS_BIG_ENDIAN)
129 /* UNALIGNED_ACCESS_IS_FAST should be defined to 1 if unaligned memory accesses
130 * can be performed efficiently on the target platform. */
131 #if defined(__x86_64__) || defined(__i386__) || defined(__ARM_FEATURE_UNALIGNED)
132 # define UNALIGNED_ACCESS_IS_FAST 1
134 # define UNALIGNED_ACCESS_IS_FAST 0
137 /* Get the type of the specified expression. */
138 #define typeof __typeof__
140 /* Get the minimum of two variables, without multiple evaluation. */
142 # define min(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
143 (_a < _b) ? _a : _b; })
146 /* Get the maximum of two variables, without multiple evaluation. */
148 # define max(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
149 (_a > _b) ? _a : _b; })
152 /* Swap the values of two variables, without multiple evaluation. */
154 # define swap(a, b) ({ typeof(a) _a = (a); (a) = (b); (b) = _a; })
157 /* (Optional) Efficiently swap the bytes of a 16-bit integer. */
158 #if GCC_PREREQ(4, 8) || __has_builtin(__builtin_bswap16)
159 # define compiler_bswap16 __builtin_bswap16
162 /* (Optional) Efficiently swap the bytes of a 32-bit integer. */
163 #if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap32)
164 # define compiler_bswap32 __builtin_bswap32
167 /* (Optional) Efficiently swap the bytes of a 64-bit integer. */
168 #if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap64)
169 # define compiler_bswap64 __builtin_bswap64
172 /* (Optional) Find Last Set bit and Find First Set bit macros. */
173 #define compiler_bsr32(n) (31 - __builtin_clz(n))
174 #define compiler_bsr64(n) (63 - __builtin_clzll(n))
175 #define compiler_bsf32(n) __builtin_ctz(n)
176 #define compiler_bsf64(n) __builtin_ctzll(n)
178 /* Optional definitions for checking with 'sparse'. */
180 # define _bitwise_attr __attribute__((bitwise))
181 # define _force_attr __attribute__((force))
183 # define _bitwise_attr
187 /* STATIC_ASSERT() - verify the truth of an expression at compilation time. */
188 #if __STDC_VERSION__ >= 201112L
189 # define STATIC_ASSERT(expr) _Static_assert((expr), "")
191 # define STATIC_ASSERT(expr) ((void)sizeof(char[1 - 2 * !(expr)]))
194 /* STATIC_ASSERT_ZERO() - verify the truth of an expression at compilation time
195 * and also produce a result of value '0' to be used in constant expressions */
196 #define STATIC_ASSERT_ZERO(expr) ((int)sizeof(char[-!(expr)]))
198 #define CONCAT_IMPL(s1, s2) s1##s2
200 /* CONCAT() - concatenate two tokens at preprocessing time. */
201 #define CONCAT(s1, s2) CONCAT_IMPL(s1, s2)
203 #endif /* _WIMLIB_COMPILER_H */