include/qemu/compiler.h

   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 #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg)
  76
  77 #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x)
  78
  79 #define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
  80                                    sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
  81
  82 #if defined(__clang__)
  83 /* clang doesn't support gnu_printf, so use printf. */
  84 # define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
  85 #else
  86 /* Use gnu_printf (qemu uses standard format strings). */
  87 # define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
  88 # if defined(_WIN32)
  89 /*
  90  * Map __printf__ to __gnu_printf__ because we want standard format strings even
  91  * when MinGW or GLib include files use __printf__.
  92  */
  93 #  define __printf__ __gnu_printf__
  94 # endif
  95 #endif
  96
  97 #ifndef __has_warning
  98 #define __has_warning(x) 0 /* compatibility with non-clang compilers */
  99 #endif
 100
 101 #ifndef __has_feature
 102 #define __has_feature(x) 0 /* compatibility with non-clang compilers */
 103 #endif
 104
 105 #ifndef __has_builtin
 106 #define __has_builtin(x) 0 /* compatibility with non-clang compilers */
 107 #endif
 108
 109 #if __has_builtin(__builtin_assume_aligned) || !defined(__clang__)
 110 #define HAS_ASSUME_ALIGNED
 111 #endif
 112
 113 #ifndef __has_attribute
 114 #define __has_attribute(x) 0 /* compatibility with older GCC */
 115 #endif
 116
 117 /*
 118  * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
 119  * versions we support have the "flatten" attribute. Clang may not have the
 120  * "flatten" attribute but always has __has_attribute() to check for it.
 121  */
 122 #if __has_attribute(flatten) || !defined(__clang__)
 123 # define QEMU_FLATTEN __attribute__((flatten))
 124 #else
 125 # define QEMU_FLATTEN
 126 #endif
 127
 128 /*
 129  * If __attribute__((error)) is present, use it to produce an error at
 130  * compile time.  Otherwise, one must wait for the linker to diagnose
 131  * the missing symbol.
 132  */
 133 #if __has_attribute(error)
 134 # define QEMU_ERROR(X) __attribute__((error(X)))
 135 #else
 136 # define QEMU_ERROR(X)
 137 #endif
 138
 139 /*
 140  * The nonstring variable attribute specifies that an object or member
 141  * declaration with type array of char or pointer to char is intended
 142  * to store character arrays that do not necessarily contain a terminating
 143  * NUL character. This is useful in detecting uses of such arrays or pointers
 144  * with functions that expect NUL-terminated strings, and to avoid warnings
 145  * when such an array or pointer is used as an argument to a bounded string
 146  * manipulation function such as strncpy.
 147  */
 148 #if __has_attribute(nonstring)
 149 # define QEMU_NONSTRING __attribute__((nonstring))
 150 #else
 151 # define QEMU_NONSTRING
 152 #endif
 153
 154 /*
 155  * Forced inlining may be desired to encourage constant propagation
 156  * of function parameters.  However, it can also make debugging harder,
 157  * so disable it for a non-optimizing build.
 158  */
 159 #if defined(__OPTIMIZE__)
 160 #define QEMU_ALWAYS_INLINE  __attribute__((always_inline))
 161 #else
 162 #define QEMU_ALWAYS_INLINE
 163 #endif
 164
 165 /**
 166  * qemu_build_not_reached()
 167  *
 168  * The compiler, during optimization, is expected to prove that a call
 169  * to this function cannot be reached and remove it.  If the compiler
 170  * supports QEMU_ERROR, this will be reported at compile time; otherwise
 171  * this will be reported at link time due to the missing symbol.
 172  */
 173 extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
 174     qemu_build_not_reached_always(void);
 175 #if defined(__OPTIMIZE__) && !defined(__NO_INLINE__)
 176 #define qemu_build_not_reached()  qemu_build_not_reached_always()
 177 #else
 178 #define qemu_build_not_reached()  g_assert_not_reached()
 179 #endif
 180
 181 /**
 182  * In most cases, normal "fallthrough" comments are good enough for
 183  * switch-case statements, but sometimes the compiler has problems
 184  * with those. In that case you can use QEMU_FALLTHROUGH instead.
 185  */
 186 #if __has_attribute(fallthrough)
 187 # define QEMU_FALLTHROUGH __attribute__((fallthrough))
 188 #else
 189 # define QEMU_FALLTHROUGH do {} while (0) /* fallthrough */
 190 #endif
 191
 192 #ifdef CONFIG_CFI
 193 /*
 194  * If CFI is enabled, use an attribute to disable cfi-icall on the following
 195  * function
 196  */
 197 #define QEMU_DISABLE_CFI __attribute__((no_sanitize("cfi-icall")))
 198 #else
 199 /* If CFI is not enabled, use an empty define to not change the behavior */
 200 #define QEMU_DISABLE_CFI
 201 #endif
 202
 203 #endif /* COMPILER_H */