Created
March 10, 2017 22:11
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| // Two techniques for using C99 variadic macros to provide a nicer interface to variadic functions. | |
| #include <stdarg.h> | |
| #include <stdio.h> | |
| enum { SENTINEL = 0xDEADBEEF }; | |
| void vprint_sentinel(void *dummy, ...) { | |
| va_list args; | |
| va_start(args, dummy); | |
| for (;;) { | |
| int x = va_arg(args, int); | |
| if (x == SENTINEL) break; | |
| printf("%d ", x); | |
| } | |
| printf("\n"); | |
| va_end(args); | |
| } | |
| #define print_sentinel(...) vprint_sentinel(0, __VA_ARGS__, SENTINEL) | |
| void vprint_length(size_t n, ...) { | |
| va_list args; | |
| va_start(args, n); | |
| for (size_t i = 0; i < n; i++) | |
| printf("%d ", va_arg(args, int)); | |
| printf("\n"); | |
| va_end(args); | |
| } | |
| // This handles a maximum of 4 arguments. | |
| #define sel(_0, _1, _2, _3, _4, ...) _4 | |
| #define len(...) sel(__VA_ARGS__, 4, 3, 2, 1, 0) | |
| #define print_length(...) vprint_length(len(__VA_ARGS__), __VA_ARGS__) | |
| int main() { | |
| print_sentinel(1, 2, 3, 4); | |
| print_length(1, 2, 3, 4); | |
| return 0; | |
| } | |
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