1 /* compiler.h: macros to abstract away compiler specifics 2 * 3 * This work is licensed under the terms of the GNU GPL, version 2 or later. 4 * See the COPYING file in the top-level directory. 5 */ 6 7 #ifndef COMPILER_H 8 #define COMPILER_H 9 10 #if defined __clang_analyzer__ || defined __COVERITY__ 11 #define QEMU_STATIC_ANALYSIS 1 12 #endif 13 14 #ifdef __cplusplus 15 #define QEMU_EXTERN_C extern "C" 16 #else 17 #define QEMU_EXTERN_C extern 18 #endif 19 20 #define QEMU_NORETURN __attribute__ ((__noreturn__)) 21 22 #define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result)) 23 24 #define QEMU_SENTINEL __attribute__((sentinel)) 25 26 #if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__)) 27 # define QEMU_PACKED __attribute__((gcc_struct, packed)) 28 #else 29 # define QEMU_PACKED __attribute__((packed)) 30 #endif 31 32 #define QEMU_ALIGNED(X) __attribute__((aligned(X))) 33 34 #ifndef glue 35 #define xglue(x, y) x ## y 36 #define glue(x, y) xglue(x, y) 37 #define stringify(s) tostring(s) 38 #define tostring(s) #s 39 #endif 40 41 #ifndef likely 42 #define likely(x) __builtin_expect(!!(x), 1) 43 #define unlikely(x) __builtin_expect(!!(x), 0) 44 #endif 45 46 #ifndef container_of 47 #define container_of(ptr, type, member) ({ \ 48 const typeof(((type *) 0)->member) *__mptr = (ptr); \ 49 (type *) ((char *) __mptr - offsetof(type, member));}) 50 #endif 51 52 #define sizeof_field(type, field) sizeof(((type *)0)->field) 53 54 /* 55 * Calculate the number of bytes up to and including the given 'field' of 56 * 'container'. 57 */ 58 #define endof(container, field) \ 59 (offsetof(container, field) + sizeof_field(container, field)) 60 61 /* Convert from a base type to a parent type, with compile time checking. */ 62 #define DO_UPCAST(type, field, dev) ( __extension__ ( { \ 63 char __attribute__((unused)) offset_must_be_zero[ \ 64 -offsetof(type, field)]; \ 65 container_of(dev, type, field);})) 66 67 #define typeof_field(type, field) typeof(((type *)0)->field) 68 #define type_check(t1,t2) ((t1*)0 - (t2*)0) 69 70 #define QEMU_BUILD_BUG_ON_STRUCT(x) \ 71 struct { \ 72 int:(x) ? -1 : 1; \ 73 } 74 75 /* QEMU_BUILD_BUG_MSG() emits the message given if _Static_assert is 76 * supported; otherwise, it will be omitted from the compiler error 77 * message (but as it remains present in the source code, it can still 78 * be useful when debugging). */ 79 #if defined(CONFIG_STATIC_ASSERT) 80 #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg) 81 #elif defined(__COUNTER__) 82 #define QEMU_BUILD_BUG_MSG(x, msg) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \ 83 glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused)) 84 #else 85 #define QEMU_BUILD_BUG_MSG(x, msg) 86 #endif 87 88 #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x) 89 90 #define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \ 91 sizeof(QEMU_BUILD_BUG_ON_STRUCT(x))) 92 93 #if defined(__clang__) 94 /* clang doesn't support gnu_printf, so use printf. */ 95 # define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m))) 96 #else 97 /* Use gnu_printf (qemu uses standard format strings). */ 98 # define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m))) 99 # if defined(_WIN32) 100 /* 101 * Map __printf__ to __gnu_printf__ because we want standard format strings even 102 * when MinGW or GLib include files use __printf__. 103 */ 104 # define __printf__ __gnu_printf__ 105 # endif 106 #endif 107 108 #ifndef __has_warning 109 #define __has_warning(x) 0 /* compatibility with non-clang compilers */ 110 #endif 111 112 #ifndef __has_feature 113 #define __has_feature(x) 0 /* compatibility with non-clang compilers */ 114 #endif 115 116 #ifndef __has_builtin 117 #define __has_builtin(x) 0 /* compatibility with non-clang compilers */ 118 #endif 119 120 #if __has_builtin(__builtin_assume_aligned) || !defined(__clang__) 121 #define HAS_ASSUME_ALIGNED 122 #endif 123 124 #ifndef __has_attribute 125 #define __has_attribute(x) 0 /* compatibility with older GCC */ 126 #endif 127 128 /* 129 * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC 130 * versions we support have the "flatten" attribute. Clang may not have the 131 * "flatten" attribute but always has __has_attribute() to check for it. 132 */ 133 #if __has_attribute(flatten) || !defined(__clang__) 134 # define QEMU_FLATTEN __attribute__((flatten)) 135 #else 136 # define QEMU_FLATTEN 137 #endif 138 139 /* 140 * If __attribute__((error)) is present, use it to produce an error at 141 * compile time. Otherwise, one must wait for the linker to diagnose 142 * the missing symbol. 143 */ 144 #if __has_attribute(error) 145 # define QEMU_ERROR(X) __attribute__((error(X))) 146 #else 147 # define QEMU_ERROR(X) 148 #endif 149 150 /* 151 * The nonstring variable attribute specifies that an object or member 152 * declaration with type array of char or pointer to char is intended 153 * to store character arrays that do not necessarily contain a terminating 154 * NUL character. This is useful in detecting uses of such arrays or pointers 155 * with functions that expect NUL-terminated strings, and to avoid warnings 156 * when such an array or pointer is used as an argument to a bounded string 157 * manipulation function such as strncpy. 158 */ 159 #if __has_attribute(nonstring) 160 # define QEMU_NONSTRING __attribute__((nonstring)) 161 #else 162 # define QEMU_NONSTRING 163 #endif 164 165 /* 166 * Forced inlining may be desired to encourage constant propagation 167 * of function parameters. However, it can also make debugging harder, 168 * so disable it for a non-optimizing build. 169 */ 170 #if defined(__OPTIMIZE__) 171 #define QEMU_ALWAYS_INLINE __attribute__((always_inline)) 172 #else 173 #define QEMU_ALWAYS_INLINE 174 #endif 175 176 /* Implement C11 _Generic via GCC builtins. Example: 177 * 178 * QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x) 179 * 180 * The first argument is the discriminator. The last is the default value. 181 * The middle ones are tuples in "(type, expansion)" format. 182 */ 183 184 /* First, find out the number of generic cases. */ 185 #define QEMU_GENERIC(x, ...) \ 186 QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) 187 188 /* There will be extra arguments, but they are not used. */ 189 #define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \ 190 QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9) 191 192 /* Two more helper macros, this time to extract items from a parenthesized 193 * list. 194 */ 195 #define QEMU_FIRST_(a, b) a 196 #define QEMU_SECOND_(a, b) b 197 198 /* ... and a final one for the common part of the "recursion". */ 199 #define QEMU_GENERIC_IF(x, type_then, else_) \ 200 __builtin_choose_expr(__builtin_types_compatible_p(x, \ 201 QEMU_FIRST_ type_then), \ 202 QEMU_SECOND_ type_then, else_) 203 204 /* CPP poor man's "recursion". */ 205 #define QEMU_GENERIC1(x, a0, ...) (a0) 206 #define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__)) 207 #define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__)) 208 #define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__)) 209 #define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__)) 210 #define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__)) 211 #define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__)) 212 #define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__)) 213 #define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__)) 214 #define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__)) 215 216 /** 217 * qemu_build_not_reached() 218 * 219 * The compiler, during optimization, is expected to prove that a call 220 * to this function cannot be reached and remove it. If the compiler 221 * supports QEMU_ERROR, this will be reported at compile time; otherwise 222 * this will be reported at link time due to the missing symbol. 223 */ 224 extern void QEMU_NORETURN QEMU_ERROR("code path is reachable") 225 qemu_build_not_reached_always(void); 226 #if defined(__OPTIMIZE__) && !defined(__NO_INLINE__) 227 #define qemu_build_not_reached() qemu_build_not_reached_always() 228 #else 229 #define qemu_build_not_reached() g_assert_not_reached() 230 #endif 231 232 /** 233 * In most cases, normal "fallthrough" comments are good enough for 234 * switch-case statements, but sometimes the compiler has problems 235 * with those. In that case you can use QEMU_FALLTHROUGH instead. 236 */ 237 #if __has_attribute(fallthrough) 238 # define QEMU_FALLTHROUGH __attribute__((fallthrough)) 239 #else 240 # define QEMU_FALLTHROUGH do {} while (0) /* fallthrough */ 241 #endif 242 243 #ifdef CONFIG_CFI 244 /* 245 * If CFI is enabled, use an attribute to disable cfi-icall on the following 246 * function 247 */ 248 #define QEMU_DISABLE_CFI __attribute__((no_sanitize("cfi-icall"))) 249 #else 250 /* If CFI is not enabled, use an empty define to not change the behavior */ 251 #define QEMU_DISABLE_CFI 252 #endif 253 254 #endif /* COMPILER_H */ 255