+ size_t used;
+
+#if HAVE_RAW_DECL_GETCWD && HAVE_MINIMALLY_WORKING_GETCWD
+ /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
+ this is much slower than the system getcwd (at least on
+ GNU/Linux). So trust the system getcwd's results unless they
+ look suspicious.
+
+ Use the system getcwd even if we have openat support, since the
+ system getcwd works even when a parent is unreadable, while the
+ openat-based approach does not.
+
+ But on AIX 5.1..7.1, the system getcwd is not even minimally
+ working: If the current directory name is slightly longer than
+ PATH_MAX, it omits the first directory component and returns
+ this wrong result with errno = 0. */
+
+# undef getcwd
+ dir = getcwd (buf, size);
+ if (dir || (size && errno == ERANGE))
+ return dir;
+
+ /* Solaris getcwd (NULL, 0) fails with errno == EINVAL, but it has
+ internal magic that lets it work even if an ancestor directory is
+ inaccessible, which is better in many cases. So in this case try
+ again with a buffer that's almost always big enough. */
+ if (errno == EINVAL && buf == NULL && size == 0)
+ {
+ char big_buffer[BIG_FILE_NAME_LENGTH + 1];
+ dir = getcwd (big_buffer, sizeof big_buffer);
+ if (dir)
+ return strdup (dir);
+ }
+
+# if HAVE_PARTLY_WORKING_GETCWD
+ /* The system getcwd works, except it sometimes fails when it
+ shouldn't, setting errno to ERANGE, ENAMETOOLONG, or ENOENT. */
+ if (errno != ERANGE && errno != ENAMETOOLONG && errno != ENOENT)
+ return NULL;
+# endif
+#endif