int xrename(const char *oldpath, const char *newpath);
int write_all(int fd, const char *buf, size_t len);
__printf_2_3 int write_va_buffer(int fd, const char *fmt, ...);
-bool file_exists(const char *);
int xpoll(struct pollfd *fds, nfds_t nfds, int timeout);
__must_check int mark_fd_nonblocking(int fd);
__must_check int mark_fd_blocking(int fd);