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)
  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_feature
 117 #define __has_feature(x) 0 /* compatibility with non-clang compilers */
 118 #endif
 119
 120 #ifndef __has_builtin
 121 #define __has_builtin(x) 0 /* compatibility with non-clang compilers */
 122 #endif
 123
 124 #if __has_builtin(__builtin_assume_aligned) || !defined(__clang__)
 125 #define HAS_ASSUME_ALIGNED
 126 #endif
 127
 128 #ifndef __has_attribute
 129 #define __has_attribute(x) 0 /* compatibility with older GCC */
 130 #endif
 131
 132 /*
 133  * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
 134  * versions we support have the "flatten" attribute. Clang may not have the
 135  * "flatten" attribute but always has __has_attribute() to check for it.
 136  */
 137 #if __has_attribute(flatten) || !defined(__clang__)
 138 # define QEMU_FLATTEN __attribute__((flatten))
 139 #else
 140 # define QEMU_FLATTEN
 141 #endif
 142
 143 /*
 144  * If __attribute__((error)) is present, use it to produce an error at
 145  * compile time.  Otherwise, one must wait for the linker to diagnose
 146  * the missing symbol.
 147  */
 148 #if __has_attribute(error)
 149 # define QEMU_ERROR(X) __attribute__((error(X)))
 150 #else
 151 # define QEMU_ERROR(X)
 152 #endif
 153
 154 /* Implement C11 _Generic via GCC builtins.  Example:
 155  *
 156  *    QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
 157  *
 158  * The first argument is the discriminator.  The last is the default value.
 159  * The middle ones are tuples in "(type, expansion)" format.
 160  */
 161
 162 /* First, find out the number of generic cases.  */
 163 #define QEMU_GENERIC(x, ...) \
 164     QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
 165
 166 /* There will be extra arguments, but they are not used.  */
 167 #define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \
 168     QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9)
 169
 170 /* Two more helper macros, this time to extract items from a parenthesized
 171  * list.
 172  */
 173 #define QEMU_FIRST_(a, b) a
 174 #define QEMU_SECOND_(a, b) b
 175
 176 /* ... and a final one for the common part of the "recursion".  */
 177 #define QEMU_GENERIC_IF(x, type_then, else_)                                   \
 178     __builtin_choose_expr(__builtin_types_compatible_p(x,                      \
 179                                                        QEMU_FIRST_ type_then), \
 180                           QEMU_SECOND_ type_then, else_)
 181
 182 /* CPP poor man's "recursion".  */
 183 #define QEMU_GENERIC1(x, a0, ...) (a0)
 184 #define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__))
 185 #define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__))
 186 #define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__))
 187 #define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__))
 188 #define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__))
 189 #define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__))
 190 #define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__))
 191 #define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__))
 192 #define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__))
 193
 194 #endif /* COMPILER_H */