4 * Compiler-specific definitions. Currently, only GCC and clang are supported.
6 * The author dedicates this file to the public domain.
7 * You can do whatever you want with this file.
10 #ifndef _WIMLIB_COMPILER_H
11 #define _WIMLIB_COMPILER_H
13 /* Is the compiler GCC of the specified version or later? This always returns
14 * false for clang, since clang is "frozen" at GNUC 4.2. The __has_*
15 * feature-test macros should be used to detect clang functionality instead. */
16 #define GCC_PREREQ(major, minor) \
17 (!defined(__clang__) && !defined(__INTEL_COMPILER) && \
18 (__GNUC__ > major || \
19 (__GNUC__ == major && __GNUC_MINOR__ >= minor)))
21 /* Feature-test macros defined by recent versions of clang. */
22 #ifndef __has_attribute
23 # define __has_attribute(attribute) 0
26 # define __has_feature(feature) 0
29 # define __has_builtin(builtin) 0
32 /* Declare that the annotated function should be exported from the shared
33 * library (or DLL). */
35 # define WIMLIBAPI __declspec(dllexport)
37 # define WIMLIBAPI __attribute__((visibility("default")))
40 /* Declare that the annotated function should be inlined. Currently, we force
41 * the compiler to honor this because we use 'inline' in highly tuned code, e.g.
42 * compression codecs. */
43 #define inline inline __attribute__((always_inline))
45 /* Declare that the annotated function should *not* be inlined. */
46 #define noinline __attribute__((noinline))
48 /* Functionally the same as 'noinline', but documents that the reason for not
49 * inlining is to prevent the annotated function from being inlined into a
50 * recursive function, thereby increasing its stack usage. */
51 #define noinline_for_stack noinline
53 /* Hint that the expression is usually true. */
54 #define likely(expr) __builtin_expect(!!(expr), 1)
56 /* Hint that the expression is usually false. */
57 #define unlikely(expr) __builtin_expect(!!(expr), 0)
59 /* Prefetch into L1 cache for read. */
60 #define prefetchr(addr) __builtin_prefetch((addr), 0)
62 /* Prefetch into L1 cache for write. */
63 #define prefetchw(addr) __builtin_prefetch((addr), 1)
65 /* Declare that the members of the annotated struct are tightly packed, and the
66 * struct itself may be misaligned. */
67 #define _packed_attribute __attribute__((packed))
69 /* Declare that the annotated variable, or variables of the annotated type, are
70 * to be aligned on n-byte boundaries. */
71 #define _aligned_attribute(n) __attribute__((aligned(n)))
73 /* Declare that pointers to the annotated type may alias other pointers. */
74 #define _may_alias_attribute __attribute__((may_alias))
76 /* Hint that the annotated function is rarely called. */
77 #if GCC_PREREQ(4, 4) || __has_attribute(cold)
78 # define _cold_attribute __attribute__((cold))
80 # define _cold_attribute
83 /* Hint that the annotated function is malloc-like: any non-null pointer it
84 * returns will not alias any pointer previously in use by the program. */
85 #define _malloc_attribute __attribute__((malloc))
87 /* Hint that the annotated function takes a printf()-like format string and
88 * arguments. This is currently disabled on Windows because MinGW does not
89 * support this attribute on functions taking wide-character strings. */
91 # define _format_attribute(type, format_str, format_start)
93 # define _format_attribute(type, format_str, format_start) \
94 __attribute__((format(type, format_str, format_start)))
97 /* Hint that the annotated function is intentionally not used. This might be
98 * the case if the function contains only static assertions. */
99 #define _unused_attribute __attribute__((unused))
101 /* Endianness definitions. Either CPU_IS_BIG_ENDIAN or CPU_IS_LITTLE_ENDIAN is
102 * set to 1. The other is set to 0. Note that newer gcc supports
103 * __BYTE_ORDER__ for easily determining the endianness; older gcc doesn't. In
104 * the latter case we fall back to a configure-time check. */
105 #ifdef __BYTE_ORDER__
106 # define CPU_IS_BIG_ENDIAN (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
107 #elif defined(HAVE_CONFIG_H)
109 # ifdef WORDS_BIGENDIAN
110 # define CPU_IS_BIG_ENDIAN 1
112 # define CPU_IS_BIG_ENDIAN 0
115 #define CPU_IS_LITTLE_ENDIAN (!CPU_IS_BIG_ENDIAN)
117 /* UNALIGNED_ACCESS_IS_FAST should be defined to 1 if unaligned memory accesses
118 * can be performed efficiently on the target platform. */
119 #if defined(__x86_64__) || defined(__i386__) || defined(__ARM_FEATURE_UNALIGNED)
120 # define UNALIGNED_ACCESS_IS_FAST 1
122 # define UNALIGNED_ACCESS_IS_FAST 0
125 /* Get the type of the specified expression. */
126 #define typeof __typeof__
128 /* Get the minimum of two variables, without multiple evaluation. */
130 # define min(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
131 (_a < _b) ? _a : _b; })
134 /* Get the maximum of two variables, without multiple evaluation. */
136 # define max(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
137 (_a > _b) ? _a : _b; })
140 /* Swap the values of two variables, without multiple evaluation. */
142 # define swap(a, b) ({ typeof(a) _a = (a); (a) = (b); (b) = _a; })
145 /* (Optional) Efficiently swap the bytes of a 16-bit integer. */
146 #if GCC_PREREQ(4, 8) || __has_builtin(__builtin_bswap16)
147 # define compiler_bswap16 __builtin_bswap16
150 /* (Optional) Efficiently swap the bytes of a 32-bit integer. */
151 #if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap32)
152 # define compiler_bswap32 __builtin_bswap32
155 /* (Optional) Efficiently swap the bytes of a 64-bit integer. */
156 #if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap64)
157 # define compiler_bswap64 __builtin_bswap64
160 /* (Optional) Find Last Set bit and Find First Set bit macros. */
161 #define compiler_fls32(n) (31 - __builtin_clz(n))
162 #define compiler_fls64(n) (63 - __builtin_clzll(n))
163 #define compiler_ffs32(n) __builtin_ctz(n)
164 #define compiler_ffs64(n) __builtin_ctzll(n)
166 /* Optional definitions for checking with 'sparse'. */
168 # define _bitwise_attr __attribute__((bitwise))
169 # define _force_attr __attribute__((force))
171 # define _bitwise_attr
175 /* STATIC_ASSERT() - verify the truth of an expression at compilation time. */
176 #if __STDC_VERSION__ >= 201112L
177 # define STATIC_ASSERT(expr) _Static_assert((expr), "")
179 # define STATIC_ASSERT(expr) ((void)sizeof(char[1 - 2 * !(expr)]))
182 #define CONCAT_IMPL(s1, s2) s1##s2
184 /* CONCAT() - concatenate two tokens at preprocessing time. */
185 #define CONCAT(s1, s2) CONCAT_IMPL(s1, s2)
187 #endif /* _WIMLIB_COMPILER_H */