Allow regexp-quote to return its argument

* src/search.c (Fregexp_quote): Only allocate a new string if needed.
* doc/lispref/searching.texi (Regexp Functions):
* etc/NEWS (Incompatible Lisp Changes): Document.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/search.c b/src/search.c
index 1e57d2ecbe5..9d95dcbca58 100644
--- a/src/search.c
+++ b/src/search.c
@@ -3138,10 +3138,12 @@ DEFUN ("regexp-quote", Fregexp_quote, Sregexp_quote, 1, 1, 0,
     }
 
   Lisp_Object result
-    = make_specified_string (temp,
-                             SCHARS (string) + backslashes_added,
-                             out - temp,
-                             STRING_MULTIBYTE (string));
+    = (backslashes_added > 0
+       ? make_specified_string (temp,
+                                SCHARS (string) + backslashes_added,
+                                out - temp,
+                                STRING_MULTIBYTE (string))
+       : string);
   SAFE_FREE ();
   return result;
 }