Add index for "\( in strings" (Bug#25195)

* doc/emacs/programs.texi (Left Margin Paren): Add index for "\( in
strings".
* doc/lispref/positions.texi (List Motion): Add index, and cross
reference.

2 files changed, 6 insertions, 1 deletions

diff --git a/doc/emacs/programs.texi b/doc/emacs/programs.texi
index 1d6f3e0459a..4c42b1078de 100644
--- a/doc/emacs/programs.texi
+++ b/doc/emacs/programs.texi
@@ -173,6 +173,7 @@ features that use them will also give you trouble.  This includes the
 indentation commands (@pxref{Program Indent}) and Font Lock mode
 (@pxref{Font Lock}).
 
+@cindex \( in strings
   The most likely problem case is when you want an opening delimiter
 at the start of a line inside a string.  To avoid trouble, put an
 escape character (@samp{\}, in C and Emacs Lisp, @samp{/} in some
diff --git a/doc/lispref/positions.texi b/doc/lispref/positions.texi
index 77077934673..a5a51f0a0bf 100644
--- a/doc/lispref/positions.texi
+++ b/doc/lispref/positions.texi
@@ -794,11 +794,15 @@ on a line that starts with a match for this regular expression,
 followed by a character with open-parenthesis syntax.
 @end defopt
 
+@cindex \( in strings
 @defopt open-paren-in-column-0-is-defun-start
 If this variable's value is non-@code{nil}, an open parenthesis in
 column 0 is considered to be the start of a defun.  If it is
 @code{nil}, an open parenthesis in column 0 has no special meaning.
-The default is @code{t}.
+The default is @code{t}.  If a string literal happens to have a
+parenthesis in column 0, escape it with backslash to avoid a false
+positive, @xref{Left Margin Paren,, Left Margin Convention, emacs, The
+GNU Emacs Manual}.
 @end defopt
 
 @defvar beginning-of-defun-function