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authorAndreas Grapentin <andreas@grapentin.org>2017-03-14 17:59:53 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2017-05-05 12:09:59 +0200
commit49e00a18708e27c815828d9440d5c9300d19547c (patch)
tree3adeead38454f6f193349419bbd596c00b48aac3 /include/qemu
parent00fcd100c3f47445f6a59d39e11601460880cfe4 (diff)
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use _Static_assert in QEMU_BUILD_BUG_ON
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>
Diffstat (limited to 'include/qemu')
-rw-r--r--include/qemu/compiler.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 18e6100..340e5fd 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -82,7 +82,9 @@
int:(x) ? -1 : 1; \
}
-#ifdef __COUNTER__
+#if defined(CONFIG_STATIC_ASSERT)
+#define QEMU_BUILD_BUG_ON(x) _Static_assert(!(x), "not expecting: " #x)
+#elif defined(__COUNTER__)
#define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
#else