merge revision(s) ec8e5f5aa64e2a54cf1e303f2b012c98e8d521ba,5a187e26adc8aa32367f294c1496935c7356d386: [Backport #15952]

	array.c: always check frozenness in Array#unshift. Fixes [Bug #15952]

	Closes: https://github.com/ruby/ruby/pull/2251

	array.c add back shared array optimization to
	 ary_ensure_room_for_unshift

	Bug fix in commit ec8e5f5aa64e2a [Bug #15952] disabled an
	optimization in this function.

	Closes: https://github.com/ruby/ruby/pull/2252

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67771 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 14 insertions, 2 deletions

diff --git a/array.c b/array.c
index 8995576363..1600e484fe 100644
--- a/array.c
+++ b/array.c
@@ -1118,6 +1118,8 @@ ary_ensure_room_for_unshift(VALUE ary, int argc)
 	rb_raise(rb_eIndexError, "index %ld too big", new_len);
     }
 
+    rb_ary_modify(ary);
+
     if (ARY_SHARED_P(ary)) {
 	VALUE shared = ARY_SHARED(ary);
 	capa = RARRAY_LEN(shared);
@@ -1128,7 +1130,6 @@ ary_ensure_room_for_unshift(VALUE ary, int argc)
 	}
     }
 
-    rb_ary_modify(ary);
     capa = ARY_CAPA(ary);
     if (capa - (capa >> 6) <= new_len) {
 	ary_double_capa(ary, new_len);
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index abd8d066fd..3212ed3aca 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -1895,6 +1895,17 @@ class TestArray < Test::Unit::TestCase
     assert_equal(@cls[@cls[1,2], nil, 'dog', 'cat'], a.unshift(@cls[1, 2]))
   end
 
+  def test_unshift_frozen
+    bug15952 = '[Bug #15952]'
+    assert_raise(FrozenError, bug15952) do
+      a = [1] * 100
+      b = a[4..-1]
+      a.replace([1])
+      b.freeze
+      b.unshift("a")
+    end
+  end
+
   def test_OR # '|'
     assert_equal(@cls[],  @cls[]  | @cls[])
     assert_equal(@cls[1], @cls[1] | @cls[])
diff --git a/version.h b/version.h
index e08522e1c5..beade843b4 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.5.6"
 #define RUBY_RELEASE_DATE "2019-08-27"
-#define RUBY_PATCHLEVEL 189
+#define RUBY_PATCHLEVEL 190
 
 #define RUBY_RELEASE_YEAR 2019
 #define RUBY_RELEASE_MONTH 8