On 19 Jan 2017 22:20, Pádraig Brady wrote: > On 19/01/17 21:52, Eric Blake wrote: > > On the qemu list, it was pointed out that code that uses > > ARRAY_CARDINALITY() might still compile even after it has been > > refactored to use a pointer (probably conversion of an array into > > dynamic allocation), but that you can add a compile-time check with > > new-enough gcc/clang to catch this. > > > > I'm also wondering if we should promote ARRAY_CARDINALITY into a > > full-fledged gnulib module (several gnulib files define it in .c files, > > but leave projects to re-define their own; coreutils' is in system.h). > > > > The qemu list spells their macro ARRAY_SIZE, and > > QEMU_BUILD_BUG_ON_ZERO(x) is equivalent to our verify_expr(!x, 0), but > > I'm wondering if we should similarly strengthen coreutils' macro (with > > appropriate guards for new-enough gcc, since we target more compilers > > than qemu): > > > > https://lists.gnu.org/archive/html/qemu-devel/2017-01/msg04118.html > > > > +/* > > + * &(x)[0] is always a pointer - if it's same type as x then the > > argument is a > > + * pointer, not an array. > > + */ > > +#define QEMU_IS_ARRAY(x) (!__builtin_types_compatible_p(typeof(x), \ > > + typeof(&(x)[0]))) > > #ifndef ARRAY_SIZE > > -#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > > +#define ARRAY_SIZE(x) ((sizeof(x) / sizeof((x)[0])) + \ > > + QEMU_BUILD_BUG_ON_ZERO(!QEMU_IS_ARRAY(x))) > > #endif > > gnulib module + extra checks + name change to ARRAY_SIZE sound good! > For a convenience feature, ARRAY_CARDINALITY is not a convenient name.
yeah, "cardinality" sounds more like someone trying to show off their familiarity with the english language ;). then again, my spell checker says it's not a word. linux, glibc, bootloaders, use ARRAY_SIZE. types use "size" -- it's size_t, not cardinality_t. this is the first time i've seen this name used myself. -mike
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