+ char tmp[buf ? 1 : PATH_MAX];
+ if (!buf) {
+ buf = tmp;
+ size = sizeof tmp;
+ } else if (!size) {
+ errno = EINVAL;
+ return 0;
+ }
+ long ret = syscall(SYS_getcwd, buf, size);
+ if (ret < 0)
+ return 0;
+ if (ret == 0 || buf[0] != '/') {
+ errno = ENOENT;
+ return 0;
+ }
+ return buf == tmp ? strdup(buf) : buf;