Comment by david2ndaccount

Right, you can work around it with things like this, but it means you’re forcing the C compiler to parse a compound literal just to get its length, 5 times! when the preprocessor already knows the length of `__VA_ARGS__`. Such contortions when you want a little bit of info that the compiler already has are what cause your compiler times to blow up if you try to do anything sophisticated with the cpp.

Your version expands `sum(1, 2, 3, 4, 5, 6)` to:

    sum(sizeof ((int []){0, 1, 2, 3, 4, 5, 6}) / sizeof *((int []){0, 1, 2, 3, 4, 5, 6}) - 1, ((int []){0, 1, 2, 3, 4, 5, 6}) + (sizeof ((int []){0, 1, 2, 3, 4, 5, 6}) / sizeof *((int []){0, 1, 2, 3, 4, 5, 6}) > 1))

whereas with __VA_COUNT__ it is just:

    sum(6, (int[]){1, 2, 3, 4, 5, 6})