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 /*----------------------------------------------------------------------------
  15 | The macro QEMU_GNUC_PREREQ tests for minimum version of the GNU C compiler.
  16 | The code is a copy of SOFTFLOAT_GNUC_PREREQ, see softfloat-macros.h.
  17 *----------------------------------------------------------------------------*/
  18 #if defined(__GNUC__) && defined(__GNUC_MINOR__)
  19 # define QEMU_GNUC_PREREQ(maj, min) \
  20          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
  21 #else
  22 # define QEMU_GNUC_PREREQ(maj, min) 0
  23 #endif
  24
  25 #define QEMU_NORETURN __attribute__ ((__noreturn__))
  26
  27 #define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
  28
  29 #define QEMU_SENTINEL __attribute__((sentinel))
  30
  31 #if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
  32 # define QEMU_PACKED __attribute__((gcc_struct, packed))
  33 #else
  34 # define QEMU_PACKED __attribute__((packed))
  35 #endif
  36
  37 #define QEMU_ALIGNED(X) __attribute__((aligned(X)))
  38
  39 #ifndef glue
  40 #define xglue(x, y) x ## y
  41 #define glue(x, y) xglue(x, y)
  42 #define stringify(s)    tostring(s)
  43 #define tostring(s)     #s
  44 #endif
  45
  46 #ifndef likely
  47 #if __GNUC__ < 3
  48 #define __builtin_expect(x, n) (x)
  49 #endif
  50
  51 #define likely(x)   __builtin_expect(!!(x), 1)
  52 #define unlikely(x)   __builtin_expect(!!(x), 0)
  53 #endif
  54
  55 #ifndef container_of
  56 #define container_of(ptr, type, member) ({                      \
  57         const typeof(((type *) 0)->member) *__mptr = (ptr);     \
  58         (type *) ((char *) __mptr - offsetof(type, member));})
  59 #endif
  60
  61 #define sizeof_field(type, field) sizeof(((type *)0)->field)
  62
  63 /* Convert from a base type to a parent type, with compile time checking.  */
  64 #ifdef __GNUC__
  65 #define DO_UPCAST(type, field, dev) ( __extension__ ( { \
  66     char __attribute__((unused)) offset_must_be_zero[ \
  67         -offsetof(type, field)]; \
  68     container_of(dev, type, field);}))
  69 #else
  70 #define DO_UPCAST(type, field, dev) container_of(dev, type, field)
  71 #endif
  72
  73 #define typeof_field(type, field) typeof(((type *)0)->field)
  74 #define type_check(t1,t2) ((t1*)0 - (t2*)0)
  75
  76 #define QEMU_BUILD_BUG_ON_STRUCT(x) \
  77     struct { \
  78         int:(x) ? -1 : 1; \
  79     }
  80
  81 /* QEMU_BUILD_BUG_MSG() emits the message given if _Static_assert is
  82  * supported; otherwise, it will be omitted from the compiler error
  83  * message (but as it remains present in the source code, it can still
  84  * be useful when debugging). */
  85 #if defined(CONFIG_STATIC_ASSERT)
  86 #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg)
  87 #elif defined(__COUNTER__)
  88 #define QEMU_BUILD_BUG_MSG(x, msg) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
  89     glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
  90 #else
  91 #define QEMU_BUILD_BUG_MSG(x, msg)
  92 #endif
  93
  94 #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x)
  95
  96 #define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
  97                                    sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
  98
  99 #if defined __GNUC__
 100 # if !QEMU_GNUC_PREREQ(4, 4)
 101    /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
 102 #  define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
 103 # else
 104    /* Use gnu_printf when supported (qemu uses standard format strings). */
 105 #  define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
 106 #  if defined(_WIN32)
 107     /* Map __printf__ to __gnu_printf__ because we want standard format strings
 108      * even when MinGW or GLib include files use __printf__. */
 109 #   define __printf__ __gnu_printf__
 110 #  endif
 111 # endif
 112 #else
 113 #define GCC_FMT_ATTR(n, m)
 114 #endif
 115
 116 #ifndef __has_warning
 117 #define __has_warning(x) 0 /* compatibility with non-clang compilers */
 118 #endif
 119
 120 #ifndef __has_feature
 121 #define __has_feature(x) 0 /* compatibility with non-clang compilers */
 122 #endif
 123
 124 #ifndef __has_builtin
 125 #define __has_builtin(x) 0 /* compatibility with non-clang compilers */
 126 #endif
 127
 128 #if __has_builtin(__builtin_assume_aligned) || !defined(__clang__)
 129 #define HAS_ASSUME_ALIGNED
 130 #endif
 131
 132 #ifndef __has_attribute
 133 #define __has_attribute(x) 0 /* compatibility with older GCC */
 134 #endif
 135
 136 /*
 137  * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
 138  * versions we support have the "flatten" attribute. Clang may not have the
 139  * "flatten" attribute but always has __has_attribute() to check for it.
 140  */
 141 #if __has_attribute(flatten) || !defined(__clang__)
 142 # define QEMU_FLATTEN __attribute__((flatten))
 143 #else
 144 # define QEMU_FLATTEN
 145 #endif
 146
 147 /*
 148  * If __attribute__((error)) is present, use it to produce an error at
 149  * compile time.  Otherwise, one must wait for the linker to diagnose
 150  * the missing symbol.
 151  */
 152 #if __has_attribute(error)
 153 # define QEMU_ERROR(X) __attribute__((error(X)))
 154 #else
 155 # define QEMU_ERROR(X)
 156 #endif
 157
 158 /*
 159  * The nonstring variable attribute specifies that an object or member
 160  * declaration with type array of char or pointer to char is intended
 161  * to store character arrays that do not necessarily contain a terminating
 162  * NUL character. This is useful in detecting uses of such arrays or pointers
 163  * with functions that expect NUL-terminated strings, and to avoid warnings
 164  * when such an array or pointer is used as an argument to a bounded string
 165  * manipulation function such as strncpy.
 166  */
 167 #if __has_attribute(nonstring)
 168 # define QEMU_NONSTRING __attribute__((nonstring))
 169 #else
 170 # define QEMU_NONSTRING
 171 #endif
 172
 173 /*
 174  * Forced inlining may be desired to encourage constant propagation
 175  * of function parameters.  However, it can also make debugging harder,
 176  * so disable it for a non-optimizing build.
 177  */
 178 #if defined(__OPTIMIZE__)
 179 #define QEMU_ALWAYS_INLINE  __attribute__((always_inline))
 180 #else
 181 #define QEMU_ALWAYS_INLINE
 182 #endif
 183
 184 /* Implement C11 _Generic via GCC builtins.  Example:
 185  *
 186  *    QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
 187  *
 188  * The first argument is the discriminator.  The last is the default value.
 189  * The middle ones are tuples in "(type, expansion)" format.
 190  */
 191
 192 /* First, find out the number of generic cases.  */
 193 #define QEMU_GENERIC(x, ...) \
 194     QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
 195
 196 /* There will be extra arguments, but they are not used.  */
 197 #define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \
 198     QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9)
 199
 200 /* Two more helper macros, this time to extract items from a parenthesized
 201  * list.
 202  */
 203 #define QEMU_FIRST_(a, b) a
 204 #define QEMU_SECOND_(a, b) b
 205
 206 /* ... and a final one for the common part of the "recursion".  */
 207 #define QEMU_GENERIC_IF(x, type_then, else_)                                   \
 208     __builtin_choose_expr(__builtin_types_compatible_p(x,                      \
 209                                                        QEMU_FIRST_ type_then), \
 210                           QEMU_SECOND_ type_then, else_)
 211
 212 /* CPP poor man's "recursion".  */
 213 #define QEMU_GENERIC1(x, a0, ...) (a0)
 214 #define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__))
 215 #define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__))
 216 #define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__))
 217 #define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__))
 218 #define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__))
 219 #define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__))
 220 #define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__))
 221 #define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__))
 222 #define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__))
 223
 224 /**
 225  * qemu_build_not_reached()
 226  *
 227  * The compiler, during optimization, is expected to prove that a call
 228  * to this function cannot be reached and remove it.  If the compiler
 229  * supports QEMU_ERROR, this will be reported at compile time; otherwise
 230  * this will be reported at link time due to the missing symbol.
 231  */
 232 #ifdef __OPTIMIZE__
 233 extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
 234     qemu_build_not_reached(void);
 235 #else
 236 #define qemu_build_not_reached()  g_assert_not_reached()
 237 #endif
 238
 239 #endif /* COMPILER_H */