merges r24509 from trunk into ruby_1_9_1.

--
* string.c (rb_str_new_frozen): must not change encoding of frozen
  shared string.  [ruby-dev:39068]

git-svn-id: http://svn.ruby-lang.org/repos/ruby/branches/ruby_1_9_1@25477 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 4 insertions, 3 deletions

diff --git a/string.c b/string.c
index 2017d1023..ba40ddd7d 100644
--- a/string.c
+++ b/string.c
@@ -666,13 +666,14 @@ rb_str_new_frozen(VALUE orig)
 	long ofs;
 	ofs = RSTRING_LEN(str) - RSTRING_LEN(orig);
 	if ((ofs > 0) || (klass != RBASIC(str)->klass) ||
-	    (!OBJ_TAINTED(str) && OBJ_TAINTED(orig))) {
+	    (!OBJ_TAINTED(str) && OBJ_TAINTED(orig)) ||
+	    ENCODING_GET(str) != ENCODING_GET(orig)) {
 	    str = str_new3(klass, str);
 	    RSTRING(str)->as.heap.ptr += ofs;
 	    RSTRING(str)->as.heap.len -= ofs;
+	    rb_enc_cr_str_exact_copy(str, orig);
+	    OBJ_INFECT(str, orig);
 	}
-	rb_enc_cr_str_exact_copy(str, orig);
-	OBJ_INFECT(str, orig);
     }
     else if (STR_EMBED_P(orig)) {
 	str = str_new(klass, RSTRING_PTR(orig), RSTRING_LEN(orig));