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compiler: rework BUG_ON using a struct 

There are theoretical concerns that some compilers might not trigger
build failures on attempts to define an array of size (x ? -1 : 1) where
x is a variable and make it a variable sized array instead. Let rewrite
using a struct with a negative bit field size instead as there are no
dynamic bit field sizes.  This is similar to what Linux does.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2017-01-19 22:56:14 +02:00
parent 60abf0a5e0
commit f291887e8e
1 changed files with 7 additions and 3 deletions
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10
include/qemu/compiler.h
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@ -85,10 +85,14 @@
#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; \
}
#ifdef __COUNTER__
#define QEMU_BUILD_BUG_ON(x) \
typedef char glue(qemu_build_bug_on__, __COUNTER__)[(x) ? -1 : 1] \
__attribute__((unused))
#define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
#else
#define QEMU_BUILD_BUG_ON(x)
#endif