* search.c (Freplace_match): Treat \? in the replacement text literally.

Fixes: debbugs:8161

etc/NEWS

@@ -482,6 +482,10 @@ inefficiency, and not namespace-clean.
 
 * Incompatible Lisp Changes in Emacs 24.2
 
+** If the NEWTEXT arg to `replace-match' contains a substring "\?",
+that substring is inserted literally even if the LITERAL arg is
+non-nil, instead of causing an error to be signaled.
+
 +++
 ** Docstrings starting with `*' no longer indicate user options.
 Only variables defined using `defcustom' are considered user options.

src/ChangeLog

@@ -1,3 +1,8 @@
+2012-08-05  Lawrence Mitchell  <wence@gmx.li>
+
+	* search.c (Freplace_match): Treat \? in the replacement text
+	literally (Bug#8161).
+
 2012-08-05  Chong Yidong  <cyd@gnu.org>
 
 	* term.c (Vsuspend_tty_functions, Vresume_tty_functions):

src/search.c

@@ -2226,6 +2226,9 @@ Otherwise treat `\\' as special:
   `\\N' means substitute what matched the Nth `\\(...\\)'.
        If Nth parens didn't match, substitute nothing.
   `\\\\' means insert one `\\'.
+  `\\?' is treated literally
+       (for compatibility with `query-replace-regexp').
+  Any other character following `\\' signals an error.
 Case conversion does not apply to these substitutions.
 
 FIXEDCASE and LITERAL are optional arguments.
@@ -2428,7 +2431,7 @@ since only regular expressions have distinguished subexpressions.  */)
 		    }
 		  else if (c == '\\')
 		    delbackslash = 1;
-		  else
+		  else if (c != '?')
 		    error ("Invalid use of `\\' in replacement text");
 		}
 	      if (substart >= 0)