diff options
Diffstat (limited to 'src/include/c.h')
| -rw-r--r-- | src/include/c.h | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/src/include/c.h b/src/include/c.h index 901d7911980..13c794d8eaa 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -225,6 +225,39 @@ #define CppConcat(x, y) x##y /* + * VA_ARGS_NARGS + * Returns the number of macro arguments it is passed. + * + * An empty argument still counts as an argument, so effectively, this is + * "one more than the number of commas in the argument list". + * + * This works for up to 63 arguments. Internally, VA_ARGS_NARGS_() is passed + * 64+N arguments, and the C99 standard only requires macros to allow up to + * 127 arguments, so we can't portably go higher. The implementation is + * pretty trivial: VA_ARGS_NARGS_() returns its 64th argument, and we set up + * the call so that that is the appropriate one of the list of constants. + * This idea is due to Laurent Deniau. + */ +#define VA_ARGS_NARGS(...) \ + VA_ARGS_NARGS_(__VA_ARGS__, \ + 63,62,61,60, \ + 59,58,57,56,55,54,53,52,51,50, \ + 49,48,47,46,45,44,43,42,41,40, \ + 39,38,37,36,35,34,33,32,31,30, \ + 29,28,27,26,25,24,23,22,21,20, \ + 19,18,17,16,15,14,13,12,11,10, \ + 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) +#define VA_ARGS_NARGS_( \ + _01,_02,_03,_04,_05,_06,_07,_08,_09,_10, \ + _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \ + _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \ + _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \ + _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \ + _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \ + _61,_62,_63, N, ...) \ + (N) + +/* * dummyret is used to set return values in macros that use ?: to make * assignments. gcc wants these to be void, other compilers like char */ |