+/* 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);
+ } else {
+ char *cwd = get_cwd();
+ if (cwd) {
+ char *abs_name = xasprintf("%s/%s", cwd, file_name);
+ free(cwd);
+ return abs_name;
+ } else {
+ return NULL;
+ }
+ }
+}
+
+