* string.c (rb_str_sub_bang): String#sub! now raises an error when

  called on a frozen string, even if no change is made.
  See [ruby-core:23657]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27559 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 0 deletions

diff --git a/string.c b/string.c
index b4e105aa78..caca178fc4 100644
--- a/string.c
+++ b/string.c
@@ -3466,6 +3466,7 @@ rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
     }
 
     pat = get_pat(argv[0], 1);
+    str_modifiable(str);
     if (rb_reg_search(pat, str, 0, 0) >= 0) {
 	rb_encoding *enc;
 	int cr = ENC_CODERANGE(str);