transcode.c (documentation for str_encode): Explain

that transcoding to the same encoding is a no-op
  (i.e. no exceptions, no replacements,...).
  [ruby-core:43557][Bug #6190]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@35121 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Fri Mar 23 15:12:12 2012  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* transcode.c (documentation for str_encode): Explain
+	  that transcoding to the same encoding is a no-op
+	  (i.e. no exceptions, no replacements,...).
+	  [ruby-core:43557][Bug #6190]
+
 Fri Mar 23 13:19:20 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* bignum.c (rb_str_to_inum): must be ASCII compatible encoding as

transcode.c

@@ -2815,6 +2815,10 @@ static VALUE encoded_dup(VALUE newstr, VALUE str, int encidx);
  *  in the source encoding. The last form by default does not raise
  *  exceptions but uses replacement strings.
  *
+ *  Please note that conversion from an encoding +enc+ to the
+ *  same encoding +enc+ is a no-op, i.e. the receiver is returned without
+ *  any changes, and no exceptions are raised, even if there are invalid bytes.
+ *
  *  The +options+ Hash gives details for conversion and can have the following
  *  keys:
  *