On 10/10/2023 9:02 am, Stefano Stabellini wrote: > On Fri, 6 Oct 2023, Nicola Vetrini wrote: >> The essential type of the result of an inequality operator is >> essentially boolean, therefore it shouldn't be used as an argument of >> the multiplication operator, which expects an integer. >> >> Signed-off-by: Nicola Vetrini <nicola.vetr...@bugseng.com> >> --- >> xen/include/xen/compat.h | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/xen/include/xen/compat.h b/xen/include/xen/compat.h >> index f2ce5bb3580a..5ffee6a9fed1 100644 >> --- a/xen/include/xen/compat.h >> +++ b/xen/include/xen/compat.h >> @@ -151,12 +151,14 @@ CHECK_NAME_(k, n, T)(k xen_ ## n *x, \ >> return x == c; \ >> } >> >> +#define SIZE_NEQUAL(a, b) \ >> + (sizeof(a) != sizeof(b) ? 1 : 0) >> #define CHECK_SIZE(name) \ >> - typedef int CHECK_NAME(name, S)[1 - (sizeof(xen_ ## name ## _t) != \ >> - sizeof(compat_ ## name ## _t)) * 2] >> + typedef int CHECK_NAME(name, S)[1 - (SIZE_NEQUAL(xen_ ## name ## _t, \ >> + compat_ ## name ## >> _t)) * 2] >> #define CHECK_SIZE_(k, n) \ >> - typedef int CHECK_NAME_(k, n, S)[1 - (sizeof(k xen_ ## n) != \ >> - sizeof(k compat_ ## n)) * 2] >> + typedef int CHECK_NAME_(k, n, S)[1 - (SIZE_NEQUAL(k xen_ ## n, \ >> + k compat_ ## n)) * 2] > I think this style is easier to read but I'll let the x86 maintainers > decide > > typedef int CHECK_NAME(name, S)[(sizeof(xen_ ## name ## _t) == \ > sizeof(compat_ ## name ## _t)) ? 1 : -1] > > Also am I reading this correctly that we are using -1 as array index? I > must have made a calculation mistake?
This is a NIH BUILD_BUG_ON(). It should be rewritten as BUILD_BUG_ON(sizeof(xen ...) != sizeof(compat ...)); which will use _Static_assert() in modern compilers. ~Andrew
