/* copied from rsync */ #include <sys/types.h> #include <stdarg.h> void foo(const char *format, ...) { va_list ap; int len; char buf[5]; va_start(ap, format); len = vsnprintf(0, 0, format, ap); va_end(ap); if (len != 5) exit(1); if (snprintf(buf, 3, "hello") != 5 || strcmp(buf, "he") != 0) exit(1); exit(0); } int main() { foo("hello"); }