On 12/12/2013 02:21 PM, vijay nag wrote:
On Thu, Dec 12, 2013 at 6:38 PM, Florian Weimer <fweimer@xxxxxxxxxx> wrote:
Is there a way to count the number of variadic macro arguments in C?
I found a way to check if the list is empty: examine
sizeof(STR((__VA_ARGS__))) where STR is a macro that stringifies its
argument. If it is 3, __VA_ARGS__ is empty. I wonder if there is a less
hackish approach.
The macro arguments are expressions, but not of a uniform type, so an
array-based approach does not work.
--
Florian Weimer / Red Hat Product Security Team
#define PP_NARG( ...) PP_NARG_(__VA_ARGS__,PP_RSEQ_N())
#define PP_NARG_(...) PP_ARG_N(__VA_ARGS__)
#define PP_ARG_N(_1,_2,_3,_4,_5,_6,_7,_8,_9,[..],_61,_62,_63,N,...) N
#define PP_RSEQ_N() 63,62,61,60,[..],9,8,7,6,5,4,3,2,1,0
Hmm. I think this returns the 64th argument if the argument list is
longer than 63. I don't want to silently produce wrong results if some
arbitrary limit is exceeded.
--
Florian Weimer / Red Hat Product Security Team
