From fdd7ffb70ca6e9f7d790aadde86dbc8172e19f4d Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Mon, 25 Mar 2024 09:24:21 +0900
Subject: [PATCH] [Bug #20389] Chilled string cannot be a shared root

---
 string.c                 |  2 +-
 test/ruby/test_string.rb | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/string.c b/string.c
index cbd8f90585..9d84b16a07 100644
--- a/string.c
+++ b/string.c
@@ -1340,7 +1340,7 @@ rb_str_new_shared(VALUE str)
 VALUE
 rb_str_new_frozen(VALUE orig)
 {
-    if (OBJ_FROZEN(orig)) return orig;
+    if (RB_FL_TEST_RAW(orig, FL_FREEZE | STR_CHILLED) == FL_FREEZE) return orig;
     return str_new_frozen(rb_obj_class(orig), orig);
 }
 
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 8df6d3277f..8ec80d06fc 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -3648,6 +3648,18 @@ CODE
     Warning[:deprecated] = deprecated
   end
 
+  def test_chilled_string_substring
+    deprecated = Warning[:deprecated]
+    Warning[:deprecated] = false
+    chilled_string = eval('"a chilled string."')
+    substring = chilled_string[0..-1]
+    assert_equal("a chilled string.", substring)
+    chilled_string[0..-1] = "This string is defrosted."
+    assert_equal("a chilled string.", substring)
+  ensure
+    Warning[:deprecated] = deprecated
+  end
+
   private
 
   def assert_bytesplice_result(expected, s, *args)