#define NULL see [support.types.nullptr] #define CLOCKS_PER_SEC see below #define TIME_UTC see below namespace std { using size_t = see [support.types.layout]; using clock_t = see below; using time_t = see below; struct timespec; struct tm; clock_t clock(); double difftime(time_t time1, time_t time0); time_t mktime(struct tm* timeptr); time_t time(time_t* timer); int timespec_get(timespec* ts, int base); char* asctime(const struct tm* timeptr); char* ctime(const time_t* timer); struct tm* gmtime(const time_t* timer); struct tm* localtime(const time_t* timer); size_t strftime(char* s, size_t maxsize, const char* format, const struct tm* timeptr); }