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 /*
  64  * Calculate the number of bytes up to and including the given 'field' of
  65  * 'container'.
  66  */
  67 #define endof(container, field) \
  68     (offsetof(container, field) + sizeof_field(container, field))
  69
  70 /* Convert from a base type to a parent type, with compile time checking.  */
  71 #ifdef __GNUC__
  72 #define DO_UPCAST(type, field, dev) ( __extension__ ( { \
  73     char __attribute__((unused)) offset_must_be_zero[ \
  74         -offsetof(type, field)]; \
  75     container_of(dev, type, field);}))
  76 #else
  77 #define DO_UPCAST(type, field, dev) container_of(dev, type, field)
  78 #endif
  79
  80 #define typeof_field(type, field) typeof(((type *)0)->field)
  81 #define type_check(t1,t2) ((t1*)0 - (t2*)0)
  82
  83 #define QEMU_BUILD_BUG_ON_STRUCT(x) \
  84     struct { \
  85         int:(x) ? -1 : 1; \
  86     }
  87
  88 /* QEMU_BUILD_BUG_MSG() emits the message given if _Static_assert is
  89  * supported; otherwise, it will be omitted from the compiler error
  90  * message (but as it remains present in the source code, it can still
  91  * be useful when debugging). */
  92 #if defined(CONFIG_STATIC_ASSERT)
  93 #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg)
  94 #elif defined(__COUNTER__)
  95 #define QEMU_BUILD_BUG_MSG(x, msg) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
  96     glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
  97 #else
  98 #define QEMU_BUILD_BUG_MSG(x, msg)
  99 #endif
 100
 101 #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x)
 102
 103 #define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
 104                                    sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
 105
 106 #if defined __GNUC__
 107 # if !QEMU_GNUC_PREREQ(4, 4)
 108    /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
 109 #  define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
 110 # else
 111    /* Use gnu_printf when supported (qemu uses standard format strings). */
 112 #  define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
 113 #  if defined(_WIN32)
 114     /* Map __printf__ to __gnu_printf__ because we want standard format strings
 115      * even when MinGW or GLib include files use __printf__. */
 116 #   define __printf__ __gnu_printf__
 117 #  endif
 118 # endif
 119 #else
 120 #define GCC_FMT_ATTR(n, m)
 121 #endif
 122
 123 #ifndef __has_warning
 124 #define __has_warning(x) 0 /* compatibility with non-clang compilers */
 125 #endif
 126
 127 #ifndef __has_feature
 128 #define __has_feature(x) 0 /* compatibility with non-clang compilers */
 129 #endif
 130
 131 #ifndef __has_builtin
 132 #define __has_builtin(x) 0 /* compatibility with non-clang compilers */
 133 #endif
 134
 135 #if __has_builtin(__builtin_assume_aligned) || !defined(__clang__)
 136 #define HAS_ASSUME_ALIGNED
 137 #endif
 138
 139 #ifndef __has_attribute
 140 #define __has_attribute(x) 0 /* compatibility with older GCC */
 141 #endif
 142
 143 /*
 144  * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
 145  * versions we support have the "flatten" attribute. Clang may not have the
 146  * "flatten" attribute but always has __has_attribute() to check for it.
 147  */
 148 #if __has_attribute(flatten) || !defined(__clang__)
 149 # define QEMU_FLATTEN __attribute__((flatten))
 150 #else
 151 # define QEMU_FLATTEN
 152 #endif
 153
 154 /*
 155  * If __attribute__((error)) is present, use it to produce an error at
 156  * compile time.  Otherwise, one must wait for the linker to diagnose
 157  * the missing symbol.
 158  */
 159 #if __has_attribute(error)
 160 # define QEMU_ERROR(X) __attribute__((error(X)))
 161 #else
 162 # define QEMU_ERROR(X)
 163 #endif
 164
 165 /*
 166  * The nonstring variable attribute specifies that an object or member
 167  * declaration with type array of char or pointer to char is intended
 168  * to store character arrays that do not necessarily contain a terminating
 169  * NUL character. This is useful in detecting uses of such arrays or pointers
 170  * with functions that expect NUL-terminated strings, and to avoid warnings
 171  * when such an array or pointer is used as an argument to a bounded string
 172  * manipulation function such as strncpy.
 173  */
 174 #if __has_attribute(nonstring)
 175 # define QEMU_NONSTRING __attribute__((nonstring))
 176 #else
 177 # define QEMU_NONSTRING
 178 #endif
 179
 180 /*
 181  * Forced inlining may be desired to encourage constant propagation
 182  * of function parameters.  However, it can also make debugging harder,
 183  * so disable it for a non-optimizing build.
 184  */
 185 #if defined(__OPTIMIZE__)
 186 #define QEMU_ALWAYS_INLINE  __attribute__((always_inline))
 187 #else
 188 #define QEMU_ALWAYS_INLINE
 189 #endif
 190
 191 /* Implement C11 _Generic via GCC builtins.  Example:
 192  *
 193  *    QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
 194  *
 195  * The first argument is the discriminator.  The last is the default value.
 196  * The middle ones are tuples in "(type, expansion)" format.
 197  */
 198
 199 /* First, find out the number of generic cases.  */
 200 #define QEMU_GENERIC(x, ...) \
 201     QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
 202
 203 /* There will be extra arguments, but they are not used.  */
 204 #define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \
 205     QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9)
 206
 207 /* Two more helper macros, this time to extract items from a parenthesized
 208  * list.
 209  */
 210 #define QEMU_FIRST_(a, b) a
 211 #define QEMU_SECOND_(a, b) b
 212
 213 /* ... and a final one for the common part of the "recursion".  */
 214 #define QEMU_GENERIC_IF(x, type_then, else_)                                   \
 215     __builtin_choose_expr(__builtin_types_compatible_p(x,                      \
 216                                                        QEMU_FIRST_ type_then), \
 217                           QEMU_SECOND_ type_then, else_)
 218
 219 /* CPP poor man's "recursion".  */
 220 #define QEMU_GENERIC1(x, a0, ...) (a0)
 221 #define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__))
 222 #define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__))
 223 #define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__))
 224 #define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__))
 225 #define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__))
 226 #define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__))
 227 #define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__))
 228 #define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__))
 229 #define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__))
 230
 231 /**
 232  * qemu_build_not_reached()
 233  *
 234  * The compiler, during optimization, is expected to prove that a call
 235  * to this function cannot be reached and remove it.  If the compiler
 236  * supports QEMU_ERROR, this will be reported at compile time; otherwise
 237  * this will be reported at link time due to the missing symbol.
 238  */
 239 #if defined(__OPTIMIZE__) && !defined(__NO_INLINE__)
 240 extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
 241     qemu_build_not_reached(void);
 242 #else
 243 #define qemu_build_not_reached()  g_assert_not_reached()
 244 #endif
 245
 246 #endif /* COMPILER_H */