print timestamp in log using C/C++

log.h

#define PRINT(tag, fmt, ...) printf("%s %s " fmt"", get_cur_time(), tag, ##__VA_ARGS__)

inline char* get_cur_time() {
  static char s[32] = {0};
  time_t t;
  struct tm* ltime;
  struct timeval stamp;
  
  gettimeofday(&stamp, NULL);
  ltime = localtime(&stamp.tv_sec);
  s[0] = '[';
  strftime(&s[1], 20, "%Y-%m-%d %H:%M:%S", ltime);
  sprintf(&s[strlen(s)], ".%03ld]", stamp.tv_usec / 1000);
  return s;
}