Question

The following (test with gcc -E blah.c):

#define UNUSED(type) type UNUSED_ ## __COUNTER__
UNUSED(char const *)
UNUSED(int)

Generates:

char const * UNUSED__COUNTER__
int UNUSED__COUNTER__

I’m expecting:

char const * UNUSED0
int UNUSED1

I’ve tried calling another macro, wrapping the arguments in brackets to no avail.
If I don’t paste the tokens it seems to work fine.
The documentation specifically mentions the use of __COUNTER__ in token pasting.

What am I doing wrong?

Answer 1

Experimenting with gcc 4.4, this works:

#define UNUSED(type) UNUSED_(type, __COUNTER__)
#define UNUSED_(type, counter) UNUSED__(type, counter)
#define UNUSED__(type, counter) type UNUSED_ ## counter
UNUSED(char const *)
UNUSED(int)

But it doesn’t work if I take out even one level of intermediates.