LXR qemu/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#ifdef __OPTIMIZE__
 240extern 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 */
 247