merges r20952 from trunk into ruby_1_9_1.

* string.c (rb_external_str_new_with_enc): set ASCII-8BIT if
  encoding is US-ASCII and string contains 8bit characters.

git-svn-id: http://svn.ruby-lang.org/repos/ruby/branches/ruby_1_9_1@21072 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 0 deletions

diff --git a/string.c b/string.c
index c1f14a852..236980e25 100644
--- a/string.c
+++ b/string.c
@@ -538,6 +538,11 @@ rb_external_str_new_with_enc(const char *ptr, long len, rb_encoding *eenc)
     VALUE str;
 
     str = rb_tainted_str_new(ptr, len);
+    if (rb_enc_str_coderange(str) != ENC_CODERANGE_7BIT &&
+	eenc == rb_usascii_encoding()) {
+	rb_enc_associate(str, rb_ascii8bit_encoding());
+	return str;
+    }
     rb_enc_associate(str, eenc);
     return rb_str_conv_enc(str, eenc, rb_default_internal_encoding());
 }