Expose rb_str_chilled_p

Some extensions (like stringio) may need to differentiate between
chilled strings and frozen strings.

They can now use rb_str_chilled_p but must check for its presence since
the function will be removed when chilled strings are removed.

[Bug #20389]

[Feature #20205]

Co-authored-by: Jean Boussier <byroot@ruby-lang.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/test/-ext-/string/test_chilled.rb b/test/-ext-/string/test_chilled.rb
new file mode 100644
index 0000000000..dccab61ced
--- /dev/null
+++ b/test/-ext-/string/test_chilled.rb
@@ -0,0 +1,19 @@
+require 'test/unit'
+require '-test-/string'
+
+class Test_String_ChilledString < Test::Unit::TestCase
+  def test_rb_str_chilled_p
+    str = ""
+    assert_equal true, Bug::String.rb_str_chilled_p(str)
+  end
+
+  def test_rb_str_chilled_p_frozen
+    str = "".freeze
+    assert_equal false, Bug::String.rb_str_chilled_p(str)
+  end
+
+  def test_rb_str_chilled_p_mutable
+    str = "".dup
+    assert_equal false, Bug::String.rb_str_chilled_p(str)
+  end
+end