b59ea3640c
Our robot reported the following compile-time warning while compiling
Qemu with -fno-inline cflags:
In function 'load_memop',
inlined from 'load_helper' at /qemu/accel/tcg/cputlb.c:1578:20,
inlined from 'full_ldub_mmu' at /qemu/accel/tcg/cputlb.c:1624:12:
/qemu/accel/tcg/cputlb.c:1502:9: error: call to 'qemu_build_not_reached' declared with attribute error: code path is reachable
qemu_build_not_reached();
^~~~~~~~~~~~~~~~~~~~~~~~
[...]
It looks like a false-positive because only (MO_UB ^ MO_BSWAP) will
hit the default case in load_memop() while need_swap (size > 1) has
already ensured that MO_UB is not involved.
So the thing is that compilers get confused by the -fno-inline and
just can't accurately evaluate memop_size(op) at compile time, and
then the qemu_build_not_reached() is wrongly triggered by (MO_UB ^
MO_BSWAP). Let's carefully don't use the compile-time assert when
no functions will be inlined into their callers.
Reported-by: Euler Robot <euler.robot@huawei.com>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Message-Id: <20200205141545.180-1-yuzenghui@huawei.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
247 lines
8.5 KiB
C
247 lines
8.5 KiB
C
/* compiler.h: macros to abstract away compiler specifics
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef COMPILER_H
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#define COMPILER_H
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#if defined __clang_analyzer__ || defined __COVERITY__
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#define QEMU_STATIC_ANALYSIS 1
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#endif
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/*----------------------------------------------------------------------------
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| The macro QEMU_GNUC_PREREQ tests for minimum version of the GNU C compiler.
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| The code is a copy of SOFTFLOAT_GNUC_PREREQ, see softfloat-macros.h.
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*----------------------------------------------------------------------------*/
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#if defined(__GNUC__) && defined(__GNUC_MINOR__)
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# define QEMU_GNUC_PREREQ(maj, min) \
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((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
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#else
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# define QEMU_GNUC_PREREQ(maj, min) 0
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#endif
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#define QEMU_NORETURN __attribute__ ((__noreturn__))
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#define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
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#define QEMU_SENTINEL __attribute__((sentinel))
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#if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
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# define QEMU_PACKED __attribute__((gcc_struct, packed))
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#else
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# define QEMU_PACKED __attribute__((packed))
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#endif
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#define QEMU_ALIGNED(X) __attribute__((aligned(X)))
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#ifndef glue
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#define xglue(x, y) x ## y
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#define glue(x, y) xglue(x, y)
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#define stringify(s) tostring(s)
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#define tostring(s) #s
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#endif
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#ifndef likely
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#if __GNUC__ < 3
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#define __builtin_expect(x, n) (x)
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#endif
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#define likely(x) __builtin_expect(!!(x), 1)
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#define unlikely(x) __builtin_expect(!!(x), 0)
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#endif
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#ifndef container_of
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#define container_of(ptr, type, member) ({ \
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const typeof(((type *) 0)->member) *__mptr = (ptr); \
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(type *) ((char *) __mptr - offsetof(type, member));})
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#endif
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#define sizeof_field(type, field) sizeof(((type *)0)->field)
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/*
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* Calculate the number of bytes up to and including the given 'field' of
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* 'container'.
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*/
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#define endof(container, field) \
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(offsetof(container, field) + sizeof_field(container, field))
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/* Convert from a base type to a parent type, with compile time checking. */
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#ifdef __GNUC__
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#define DO_UPCAST(type, field, dev) ( __extension__ ( { \
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char __attribute__((unused)) offset_must_be_zero[ \
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-offsetof(type, field)]; \
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container_of(dev, type, field);}))
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#else
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#define DO_UPCAST(type, field, dev) container_of(dev, type, field)
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#endif
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#define typeof_field(type, field) typeof(((type *)0)->field)
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#define type_check(t1,t2) ((t1*)0 - (t2*)0)
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#define QEMU_BUILD_BUG_ON_STRUCT(x) \
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struct { \
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int:(x) ? -1 : 1; \
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}
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/* QEMU_BUILD_BUG_MSG() emits the message given if _Static_assert is
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* supported; otherwise, it will be omitted from the compiler error
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* message (but as it remains present in the source code, it can still
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* be useful when debugging). */
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#if defined(CONFIG_STATIC_ASSERT)
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#define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg)
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#elif defined(__COUNTER__)
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#define QEMU_BUILD_BUG_MSG(x, msg) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
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glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
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#else
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#define QEMU_BUILD_BUG_MSG(x, msg)
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#endif
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#define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x)
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#define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
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sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
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#if defined __GNUC__
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# if !QEMU_GNUC_PREREQ(4, 4)
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/* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
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# define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
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# else
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/* Use gnu_printf when supported (qemu uses standard format strings). */
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# define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
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# if defined(_WIN32)
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/* Map __printf__ to __gnu_printf__ because we want standard format strings
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* even when MinGW or GLib include files use __printf__. */
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# define __printf__ __gnu_printf__
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# endif
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# endif
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#else
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#define GCC_FMT_ATTR(n, m)
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#endif
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#ifndef __has_warning
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#define __has_warning(x) 0 /* compatibility with non-clang compilers */
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#endif
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#ifndef __has_feature
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#define __has_feature(x) 0 /* compatibility with non-clang compilers */
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#endif
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#ifndef __has_builtin
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#define __has_builtin(x) 0 /* compatibility with non-clang compilers */
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#endif
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#if __has_builtin(__builtin_assume_aligned) || !defined(__clang__)
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#define HAS_ASSUME_ALIGNED
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#endif
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#ifndef __has_attribute
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#define __has_attribute(x) 0 /* compatibility with older GCC */
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#endif
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/*
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* GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
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* versions we support have the "flatten" attribute. Clang may not have the
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* "flatten" attribute but always has __has_attribute() to check for it.
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*/
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#if __has_attribute(flatten) || !defined(__clang__)
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# define QEMU_FLATTEN __attribute__((flatten))
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#else
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# define QEMU_FLATTEN
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#endif
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/*
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* If __attribute__((error)) is present, use it to produce an error at
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* compile time. Otherwise, one must wait for the linker to diagnose
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* the missing symbol.
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*/
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#if __has_attribute(error)
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# define QEMU_ERROR(X) __attribute__((error(X)))
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#else
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# define QEMU_ERROR(X)
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#endif
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/*
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* The nonstring variable attribute specifies that an object or member
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* declaration with type array of char or pointer to char is intended
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* to store character arrays that do not necessarily contain a terminating
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* NUL character. This is useful in detecting uses of such arrays or pointers
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* with functions that expect NUL-terminated strings, and to avoid warnings
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* when such an array or pointer is used as an argument to a bounded string
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* manipulation function such as strncpy.
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*/
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#if __has_attribute(nonstring)
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# define QEMU_NONSTRING __attribute__((nonstring))
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#else
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# define QEMU_NONSTRING
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#endif
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/*
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* Forced inlining may be desired to encourage constant propagation
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* of function parameters. However, it can also make debugging harder,
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* so disable it for a non-optimizing build.
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*/
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#if defined(__OPTIMIZE__)
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#define QEMU_ALWAYS_INLINE __attribute__((always_inline))
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#else
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#define QEMU_ALWAYS_INLINE
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#endif
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/* Implement C11 _Generic via GCC builtins. Example:
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*
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* QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
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*
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* The first argument is the discriminator. The last is the default value.
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* The middle ones are tuples in "(type, expansion)" format.
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*/
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/* First, find out the number of generic cases. */
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#define QEMU_GENERIC(x, ...) \
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QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
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/* There will be extra arguments, but they are not used. */
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#define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \
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QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9)
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/* Two more helper macros, this time to extract items from a parenthesized
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* list.
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*/
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#define QEMU_FIRST_(a, b) a
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#define QEMU_SECOND_(a, b) b
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/* ... and a final one for the common part of the "recursion". */
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#define QEMU_GENERIC_IF(x, type_then, else_) \
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__builtin_choose_expr(__builtin_types_compatible_p(x, \
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QEMU_FIRST_ type_then), \
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QEMU_SECOND_ type_then, else_)
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/* CPP poor man's "recursion". */
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#define QEMU_GENERIC1(x, a0, ...) (a0)
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#define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__))
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#define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__))
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#define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__))
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#define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__))
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#define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__))
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#define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__))
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#define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__))
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#define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__))
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#define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__))
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/**
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* qemu_build_not_reached()
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*
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* The compiler, during optimization, is expected to prove that a call
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* to this function cannot be reached and remove it. If the compiler
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* supports QEMU_ERROR, this will be reported at compile time; otherwise
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* this will be reported at link time due to the missing symbol.
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*/
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#if defined(__OPTIMIZE__) && !defined(__NO_INLINE__)
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extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
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qemu_build_not_reached(void);
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#else
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#define qemu_build_not_reached() g_assert_not_reached()
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#endif
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#endif /* COMPILER_H */
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