On 19 January 2017 at 08:20, Markus Armbruster <arm...@redhat.com> wrote: > "Michael S. Tsirkin" <m...@redhat.com> writes: > >> It's a familiar pattern: some code uses ARRAY_SIZE, then refactoring >> changes the argument from an array to a pointer to a dynamically >> allocated buffer. Code keeps compiling but any ARRAY_SIZE calls now >> return the size of the pointer divided by element size. >> >> Let's add build time checks to ARRAY_SIZE before we allow more >> of these in the code-base. > > Yes, please! > >> Signed-off-by: Michael S. Tsirkin <m...@redhat.com> >> --- >> include/qemu/osdep.h | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h >> index 689f253..24bfda0 100644 >> --- a/include/qemu/osdep.h >> +++ b/include/qemu/osdep.h >> @@ -199,7 +199,13 @@ extern int daemon(int, int); >> #endif >> >> #ifndef ARRAY_SIZE >> -#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) >> +/* >> + * &(x)[0] is always a pointer - if it's same type as x then the argument >> is a >> + * pointer, not an array as expected. >> + */ >> +#define ARRAY_SIZE(x) ((sizeof(x) / sizeof((x)[0])) + >> QEMU_BUILD_BUG_ON_ZERO( \ >> + __builtin_types_compatible_p(typeof(x), \ >> + typeof(&(x)[0])))) > > Please break the line near the operator, not within one of its operands: > > #define ARRAY_SIZE(x) ((sizeof(x) / sizeof((x)[0])) \ > + QEMU_BUILD_BUG_ON_ZERO( \ > __builtin_types_compatible_p(typeof(x), \ > typeof(&(x)[0]))))
The other possible approach to the long-lines issue would be to do what the Linux kernel does and abstract out a MUST_BE_ARRAY() macro. thanks -- PMM