49e00a1870
QEMU_BUILD_BUG_ON should use C11's _Static_assert, if the compiler supports it,
to provide more readable messages on failure.
We check for _Static_assert in configure, and set CONFIG_STATIC_ASSERT
accordingly. QEMU_BUILD_BUG_ON invokes _Static_assert if CONFIG_STATIC_ASSERT
is defined, and reverts to the old way otherwise.
That way, systems without C11 conforming compiler will still have the old
messages, as verified by intentionally breaking the configure check.
the following example output was generated by inverting the condition in
QEMU_BUILD_BUG_ON:
without _Static_assert:
> In file included from /qemu/include/qemu/osdep.h:36:0,
> from /qemu/qga/commands.c:13:
> /qemu/qga/commands.c: In function ‘qmp_guest_exec_status’:
> /qemu/include/qemu/compiler.h:89:12: error: negative width in bit-field ‘<anonymous>’
> struct { \
> ^
> /qemu/include/qemu/compiler.h:96:38: note: in expansion of macro QEMU_BUILD_BUG_ON_STRUCT’
> #define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
> ^~~~~~~~~~~~~~~~~~~~~~~~
> /qemu/include/qemu/atomic.h:146:5: note: in expansion of macro ‘QEMU_BUILD_BUG_ON’
> QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
> ^~~~~~~~~~~~~~~~~
> /qemu/include/qemu/atomic.h:417:5: note: in expansion of macro ‘atomic_load_acquire’
> atomic_load_acquire(ptr)
> ^~~~~~~~~~~~~~~~~~~
> /qemu/qga/commands.c:160:21: note: in expansion of macro ‘atomic_mb_read’
> bool finished = atomic_mb_read(&gei->finished);
> ^~~~~~~~~~~~~~
with _Static_assert:
> In file included from /qemu/include/qemu/osdep.h:36:0,
> from /qemu/qga/commands.c:13:
> /qemu/qga/commands.c: In function ‘qmp_guest_exec_status’:
> /qemu/include/qemu/compiler.h:94:30: error: static assertion failed: "not expecting: sizeof(*&gei->finished) > sizeof(void *)"
> #define QEMU_BUILD_BUG_ON(x) _Static_assert((x), #x)
> ^
> /qemu/include/qemu/atomic.h:146:5: note: in expansion of macro ‘QEMU_BUILD_BUG_ON’
> QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
> ^~~~~~~~~~~~~~~~~
> /qemu/include/qemu/atomic.h:417:5: note: in expansion of macro ‘atomic_load_acquire’
> atomic_load_acquire(ptr)
> ^~~~~~~~~~~~~~~~~~~
> /qemu/qga/commands.c:160:21: note: in expansion of macro ‘atomic_mb_read’
> bool finished = atomic_mb_read(&gei->finished);
> ^~~~~~~~~~~~~~
Signed-off-by: Andreas Grapentin <andreas@grapentin.org>
Message-Id: <20170314165953.18506-1-andreas@grapentin.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
115 lines
3.4 KiB
C
115 lines
3.4 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 QEMU_GNUC_PREREQ(4, 3)
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#define QEMU_ARTIFICIAL __attribute__((always_inline, artificial))
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#else
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#define QEMU_ARTIFICIAL
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#endif
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#if defined(_WIN32)
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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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/* 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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#if defined(CONFIG_STATIC_ASSERT)
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#define QEMU_BUILD_BUG_ON(x) _Static_assert(!(x), "not expecting: " #x)
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#elif defined(__COUNTER__)
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#define QEMU_BUILD_BUG_ON(x) 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_ON(x)
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#endif
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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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#endif /* COMPILER_H */
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