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 QEMU_GNUC_PREREQ(4, 3)
  32 #define QEMU_ARTIFICIAL __attribute__((always_inline, artificial))
  33 #else
  34 #define QEMU_ARTIFICIAL
  35 #endif
  36
  37 #if defined(_WIN32)
  38 # define QEMU_PACKED __attribute__((gcc_struct, packed))
  39 #else
  40 # define QEMU_PACKED __attribute__((packed))
  41 #endif
  42
  43 #define QEMU_ALIGNED(X) __attribute__((aligned(X)))
  44
  45 #ifndef glue
  46 #define xglue(x, y) x ## y
  47 #define glue(x, y) xglue(x, y)
  48 #define stringify(s)    tostring(s)
  49 #define tostring(s)     #s
  50 #endif
  51
  52 #ifndef likely
  53 #if __GNUC__ < 3
  54 #define __builtin_expect(x, n) (x)
  55 #endif
  56
  57 #define likely(x)   __builtin_expect(!!(x), 1)
  58 #define unlikely(x)   __builtin_expect(!!(x), 0)
  59 #endif
  60
  61 #ifndef container_of
  62 #define container_of(ptr, type, member) ({                      \
  63         const typeof(((type *) 0)->member) *__mptr = (ptr);     \
  64         (type *) ((char *) __mptr - offsetof(type, member));})
  65 #endif
  66
  67 #define sizeof_field(type, field) sizeof(((type *)0)->field)
  68
  69 /* Convert from a base type to a parent type, with compile time checking.  */
  70 #ifdef __GNUC__
  71 #define DO_UPCAST(type, field, dev) ( __extension__ ( { \
  72     char __attribute__((unused)) offset_must_be_zero[ \
  73         -offsetof(type, field)]; \
  74     container_of(dev, type, field);}))
  75 #else
  76 #define DO_UPCAST(type, field, dev) container_of(dev, type, field)
  77 #endif
  78
  79 #define typeof_field(type, field) typeof(((type *)0)->field)
  80 #define type_check(t1,t2) ((t1*)0 - (t2*)0)
  81
  82 #define QEMU_BUILD_BUG_ON_STRUCT(x) \
  83     struct { \
  84         int:(x) ? -1 : 1; \
  85     }
  86
  87 /* QEMU_BUILD_BUG_MSG() emits the message given if _Static_assert is
  88  * supported; otherwise, it will be omitted from the compiler error
  89  * message (but as it remains present in the source code, it can still
  90  * be useful when debugging). */
  91 #if defined(CONFIG_STATIC_ASSERT)
  92 #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg)
  93 #elif defined(__COUNTER__)
  94 #define QEMU_BUILD_BUG_MSG(x, msg) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
  95     glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
  96 #else
  97 #define QEMU_BUILD_BUG_MSG(x, msg)
  98 #endif
  99
 100 #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x)
 101
 102 #define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
 103                                    sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
 104
 105 #if defined __GNUC__
 106 # if !QEMU_GNUC_PREREQ(4, 4)
 107    /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
 108 #  define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
 109 # else
 110    /* Use gnu_printf when supported (qemu uses standard format strings). */
 111 #  define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
 112 #  if defined(_WIN32)
 113     /* Map __printf__ to __gnu_printf__ because we want standard format strings
 114      * even when MinGW or GLib include files use __printf__. */
 115 #   define __printf__ __gnu_printf__
 116 #  endif
 117 # endif
 118 #else
 119 #define GCC_FMT_ATTR(n, m)
 120 #endif
 121
 122 #ifndef __has_feature
 123 #define __has_feature(x) 0 /* compatibility with non-clang compilers */
 124 #endif
 125
 126 #ifndef __has_builtin
 127 #define __has_builtin(x) 0 /* compatibility with non-clang compilers */
 128 #endif
 129
 130 #if __has_builtin(__builtin_assume_aligned) || QEMU_GNUC_PREREQ(4, 7)
 131 #define HAS_ASSUME_ALIGNED
 132 #endif
 133
 134 #ifndef __has_attribute
 135 #define __has_attribute(x) 0 /* compatibility with older GCC */
 136 #endif
 137
 138 /*
 139  * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
 140  * versions we support have the "flatten" attribute. Clang may not have the
 141  * "flatten" attribute but always has __has_attribute() to check for it.
 142  */
 143 #if __has_attribute(flatten) || !defined(__clang__)
 144 # define QEMU_FLATTEN __attribute__((flatten))
 145 #else
 146 # define QEMU_FLATTEN
 147 #endif
 148
 149 /*
 150  * If __attribute__((error)) is present, use it to produce an error at
 151  * compile time.  Otherwise, one must wait for the linker to diagnose
 152  * the missing symbol.
 153  */
 154 #if __has_attribute(error)
 155 # define QEMU_ERROR(X) __attribute__((error(X)))
 156 #else
 157 # define QEMU_ERROR(X)
 158 #endif
 159
 160 /* Implement C11 _Generic via GCC builtins.  Example:
 161  *
 162  *    QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
 163  *
 164  * The first argument is the discriminator.  The last is the default value.
 165  * The middle ones are tuples in "(type, expansion)" format.
 166  */
 167
 168 /* First, find out the number of generic cases.  */
 169 #define QEMU_GENERIC(x, ...) \
 170     QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
 171
 172 /* There will be extra arguments, but they are not used.  */
 173 #define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \
 174     QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9)
 175
 176 /* Two more helper macros, this time to extract items from a parenthesized
 177  * list.
 178  */
 179 #define QEMU_FIRST_(a, b) a
 180 #define QEMU_SECOND_(a, b) b
 181
 182 /* ... and a final one for the common part of the "recursion".  */
 183 #define QEMU_GENERIC_IF(x, type_then, else_)                                   \
 184     __builtin_choose_expr(__builtin_types_compatible_p(x,                      \
 185                                                        QEMU_FIRST_ type_then), \
 186                           QEMU_SECOND_ type_then, else_)
 187
 188 /* CPP poor man's "recursion".  */
 189 #define QEMU_GENERIC1(x, a0, ...) (a0)
 190 #define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__))
 191 #define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__))
 192 #define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__))
 193 #define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__))
 194 #define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__))
 195 #define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__))
 196 #define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__))
 197 #define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__))
 198 #define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__))
 199
 200 #endif /* COMPILER_H */