+ return len ? xmemdup0(file_name, len) : all_slashes_name(file_name);
+}
+
+/* Returns the file name portion of 'file_name' as a malloc()'d string,
+ * similar to the POSIX basename() function but thread-safe. */
+char *
+base_name(const char *file_name)
+{
+ size_t end, start;
+
+ end = strlen(file_name);
+ while (end > 0 && file_name[end - 1] == '/') {
+ end--;
+ }
+
+ if (!end) {
+ return all_slashes_name(file_name);
+ }
+
+ start = end;
+ while (start > 0 && file_name[start - 1] != '/') {
+ start--;
+ }
+
+ return xmemdup0(file_name + start, end - start);
+}
+
+/* If 'file_name' starts with '/', returns a copy of 'file_name'. Otherwise,
+ * returns an absolute path to 'file_name' considering it relative to 'dir',
+ * which itself must be absolute. 'dir' may be null or the empty string, in
+ * which case the current working directory is used.
+ *
+ * Returns a null pointer if 'dir' is null and getcwd() fails. */
+char *
+abs_file_name(const char *dir, const char *file_name)
+{
+ if (file_name[0] == '/') {
+ return xstrdup(file_name);
+ } else if (dir && dir[0]) {
+ char *separator = dir[strlen(dir) - 1] == '/' ? "" : "/";
+ return xasprintf("%s%s%s", dir, separator, file_name);