chedi toueiti <chedi.toueiti@xxxxxxxxx> writes:
> I'm trying to write a macro to process a variable argument list but
> need to know exactly the number of argument supplied.
> Is there any way to do so with gcc ??
If all the args are convertible to the same type, you can do
something like this:
#define COUNT_ARGS(...) (sizeof (char []) { __VA_ARGS__ })
Curiously, if I do "return COUNT_ARGS(42, 69, 105, 491);",
gcc-4.4.3 -Wall -Wextra does not warn that the last number
does not fit in char.
With C++, overloading the comma operator seems like a solution:
#include <stdio.h>
template <int C>
struct count_args
{
char n[C];
template <typename A> count_args <C + 1> operator , (A) const;
};
#define COUNT_ARGS(...) (sizeof (count_args <0> (), __VA_ARGS__).n)
int main()
{
return COUNT_ARGS("hobby", -55, printf);
}
I suspect that argument packs and constexpr in C++0x make it
possible to write this in a nicer way.
