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xemu/include/qemu/compiler.h
Paolo Bonzini 875df03b22 osdep: protect qemu/osdep.h with extern "C" 
System headers may include templates if compiled with a C++ compiler,
which cause the compiler to complain if qemu/osdep.h is included
within a C++ source file's 'extern "C"' block.  Add
an 'extern "C"' block directly to qemu/osdep.h, so that
system headers can be kept out of it.

There is a stray declaration early in qemu/osdep.h, which needs
to be special cased.  Add a definition in qemu/compiler.h to
make it look nice.

config-host.h, CONFIG_TARGET, exec/poison.h and qemu/compiler.h
are included outside the 'extern "C"' block; that is not
an issue because they consist entirely of preprocessor directives.

This allows us to move the include of osdep.h in our two C++
source files outside the extern "C" block they were previously
using for it, which in turn means that they compile successfully
against newer versions of glib which insist that glib.h is
*not* inside an extern "C" block.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210416135543.20382-3-peter.maydell@linaro.org
[PMM: Moved disas/arm-a64.cc osdep.h include out of its extern "C" block;
 explained in commit message why we're doing this]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-04-17 18:44:30 +01:00

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/* compiler.h: macros to abstract away compiler specifics
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef COMPILER_H
#define COMPILER_H
#if defined __clang_analyzer__ || defined __COVERITY__
#define QEMU_STATIC_ANALYSIS 1
#endif
#ifdef __cplusplus
#define QEMU_EXTERN_C extern "C"
#else
#define QEMU_EXTERN_C extern
#endif
#define QEMU_NORETURN __attribute__ ((__noreturn__))
#define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
#define QEMU_SENTINEL __attribute__((sentinel))
#if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
# define QEMU_PACKED __attribute__((gcc_struct, packed))
#else
# define QEMU_PACKED __attribute__((packed))
#endif
#define QEMU_ALIGNED(X) __attribute__((aligned(X)))
#ifndef glue
#define xglue(x, y) x ## y
#define glue(x, y) xglue(x, y)
#define stringify(s) tostring(s)
#define tostring(s) #s
#endif
#ifndef likely
#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
#endif
#ifndef container_of
#define container_of(ptr, type, member) ({ \
const typeof(((type *) 0)->member) *__mptr = (ptr); \
(type *) ((char *) __mptr - offsetof(type, member));})
#endif
#define sizeof_field(type, field) sizeof(((type *)0)->field)
/*
* Calculate the number of bytes up to and including the given 'field' of
* 'container'.
*/
#define endof(container, field) \
(offsetof(container, field) + sizeof_field(container, field))
/* Convert from a base type to a parent type, with compile time checking. */
#define DO_UPCAST(type, field, dev) ( __extension__ ( { \
char __attribute__((unused)) offset_must_be_zero[ \
-offsetof(type, field)]; \
container_of(dev, type, field);}))
#define typeof_field(type, field) typeof(((type *)0)->field)
#define type_check(t1,t2) ((t1*)0 - (t2*)0)
#define QEMU_BUILD_BUG_ON_STRUCT(x) \
struct { \
int:(x) ? -1 : 1; \
}
/* QEMU_BUILD_BUG_MSG() emits the message given if _Static_assert is
* supported; otherwise, it will be omitted from the compiler error
* message (but as it remains present in the source code, it can still
* be useful when debugging). */
#if defined(CONFIG_STATIC_ASSERT)
#define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg)
#elif defined(__COUNTER__)
#define QEMU_BUILD_BUG_MSG(x, msg) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
#else
#define QEMU_BUILD_BUG_MSG(x, msg)
#endif
#define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x)
#define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \
sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)))
#if defined(__clang__)
/* clang doesn't support gnu_printf, so use printf. */
# define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
#else
/* Use gnu_printf (qemu uses standard format strings). */
# define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
# if defined(_WIN32)
/*
* Map __printf__ to __gnu_printf__ because we want standard format strings even
* when MinGW or GLib include files use __printf__.
*/
# define __printf__ __gnu_printf__
# endif
#endif
#ifndef __has_warning
#define __has_warning(x) 0 /* compatibility with non-clang compilers */
#endif
#ifndef __has_feature
#define __has_feature(x) 0 /* compatibility with non-clang compilers */
#endif
#ifndef __has_builtin
#define __has_builtin(x) 0 /* compatibility with non-clang compilers */
#endif
#if __has_builtin(__builtin_assume_aligned) || !defined(__clang__)
#define HAS_ASSUME_ALIGNED
#endif
#ifndef __has_attribute
#define __has_attribute(x) 0 /* compatibility with older GCC */
#endif
/*
* GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
* versions we support have the "flatten" attribute. Clang may not have the
* "flatten" attribute but always has __has_attribute() to check for it.
*/
#if __has_attribute(flatten) || !defined(__clang__)
# define QEMU_FLATTEN __attribute__((flatten))
#else
# define QEMU_FLATTEN
#endif
/*
* If __attribute__((error)) is present, use it to produce an error at
* compile time. Otherwise, one must wait for the linker to diagnose
* the missing symbol.
*/
#if __has_attribute(error)
# define QEMU_ERROR(X) __attribute__((error(X)))
#else
# define QEMU_ERROR(X)
#endif
/*
* The nonstring variable attribute specifies that an object or member
* declaration with type array of char or pointer to char is intended
* to store character arrays that do not necessarily contain a terminating
* NUL character. This is useful in detecting uses of such arrays or pointers
* with functions that expect NUL-terminated strings, and to avoid warnings
* when such an array or pointer is used as an argument to a bounded string
* manipulation function such as strncpy.
*/
#if __has_attribute(nonstring)
# define QEMU_NONSTRING __attribute__((nonstring))
#else
# define QEMU_NONSTRING
#endif
/*
* Forced inlining may be desired to encourage constant propagation
* of function parameters. However, it can also make debugging harder,
* so disable it for a non-optimizing build.
*/
#if defined(__OPTIMIZE__)
#define QEMU_ALWAYS_INLINE __attribute__((always_inline))
#else
#define QEMU_ALWAYS_INLINE
#endif
/* Implement C11 _Generic via GCC builtins. Example:
*
* QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
*
* The first argument is the discriminator. The last is the default value.
* The middle ones are tuples in "(type, expansion)" format.
*/
/* First, find out the number of generic cases. */
#define QEMU_GENERIC(x, ...) \
QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
/* There will be extra arguments, but they are not used. */
#define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \
QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9)
/* Two more helper macros, this time to extract items from a parenthesized
* list.
*/
#define QEMU_FIRST_(a, b) a
#define QEMU_SECOND_(a, b) b
/* ... and a final one for the common part of the "recursion". */
#define QEMU_GENERIC_IF(x, type_then, else_) \
__builtin_choose_expr(__builtin_types_compatible_p(x, \
QEMU_FIRST_ type_then), \
QEMU_SECOND_ type_then, else_)
/* CPP poor man's "recursion". */
#define QEMU_GENERIC1(x, a0, ...) (a0)
#define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__))
#define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__))
#define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__))
#define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__))
#define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__))
#define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__))
#define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__))
#define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__))
#define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__))
/**
* qemu_build_not_reached()
*
* The compiler, during optimization, is expected to prove that a call
* to this function cannot be reached and remove it. If the compiler
* supports QEMU_ERROR, this will be reported at compile time; otherwise
* this will be reported at link time due to the missing symbol.
*/
extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
qemu_build_not_reached_always(void);
#if defined(__OPTIMIZE__) && !defined(__NO_INLINE__)
#define qemu_build_not_reached() qemu_build_not_reached_always()
#else
#define qemu_build_not_reached() g_assert_not_reached()
#endif
/**
* In most cases, normal "fallthrough" comments are good enough for
* switch-case statements, but sometimes the compiler has problems
* with those. In that case you can use QEMU_FALLTHROUGH instead.
*/
#if __has_attribute(fallthrough)
# define QEMU_FALLTHROUGH __attribute__((fallthrough))
#else
# define QEMU_FALLTHROUGH do {} while (0) /* fallthrough */
#endif
#ifdef CONFIG_CFI
/*
* If CFI is enabled, use an attribute to disable cfi-icall on the following
* function
*/
#define QEMU_DISABLE_CFI __attribute__((no_sanitize("cfi-icall")))
#else
/* If CFI is not enabled, use an empty define to not change the behavior */
#define QEMU_DISABLE_CFI
#endif
#endif /* COMPILER_H */
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