(Creating Strings): Null strings from concat not unique.

2 files changed, 6 insertions, 1 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 282fa19bfa1..5f52b30d60a 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,7 @@
+2007-10-31  Richard Stallman  <rms@gnu.org>
+
+        * strings.texi (Creating Strings): Null strings from concat not unique.
+
 2007-10-26  Richard Stallman  <rms@gnu.org>
 
         * objects.texi (Equality Predicates): Null strings are uniquified.
diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index b2f32ad02d6..f119b3ab84b 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -259,7 +259,8 @@ returns an empty string.
 
 @noindent
 The @code{concat} function always constructs a new string that is
-not @code{eq} to any existing string.
+not @code{eq} to any existing string, except when the result is empty
+(since empty strings are canonicalized to save space).
 
 In Emacs versions before 21, when an argument was an integer (not a
 sequence of integers), it was converted to a string of digits making up