"Michael S. Tsirkin" <m...@redhat.com> writes: > There are theoretical concerns that some compilers might not trigger > build failures on attempts to define an array of size -1 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 <m...@redhat.com> > --- > include/qemu/compiler.h | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h > index 7512082..c6f673e 100644 > --- a/include/qemu/compiler.h > +++ b/include/qemu/compiler.h > @@ -85,9 +85,12 @@ > #define typeof_field(type, field) typeof(((type *)0)->field) > #define type_check(t1,t2) ((t1*)0 - (t2*)0) > > -#define QEMU_BUILD_BUG_ON(x) \ > - typedef char glue(qemu_build_bug_on__, __LINE__)[(x) ? -1 : 1] \ > - __attribute__((unused)) > +#define QEMU_BUILD_BUG_ON_STRUCT(x) \ > + struct { \ > + int qemu_build_bug_on : (x) ? -1 : 1; \ > + }
The qemu_build_bug_on name space pollution is harmless, but quite unnecessary: the name can be simply omitted (unnamed bit-field). > +#define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \ > + glue(qemu_build_bug_on__, __LINE__) __attribute__((unused)) > > #if defined __GNUC__ > # if !QEMU_GNUC_PREREQ(4, 4)