pidfile_path
const char * pidfile_path(void);
assert(pidfile_path == NULL);
pidfile_path = httpd->pidfile;
pidfile_path, pidfile_pid));
static const char* pidfile_path = NULL;
if (pidfile_path != NULL && pidfile_pid == getpid()) {
(void)unlink(pidfile_path);
pidfile_path = NULL;