merge revision(s) 82b57d7bfeefd717c10f7a5a3484aca6b3e708a3: [Backport… (#9795)

merge revision(s) 82b57d7bfeefd717c10f7a5a3484aca6b3e708a3: [Backport #20162]

	Fix memory leak when duplicating too complex object

	[Bug #20162]

	Creating a ST table then calling st_replace leaks memory because the
	st_replace overwrites the ST table without freeing any of the existing
	memory. This commit changes it to use st_copy instead.

	For example:

	    RubyVM::Shape.exhaust_shapes

	    o = Object.new
	    o.instance_variable_set(:@a, 0)

	    10.times do
	      100_000.times { o.dup }

	      puts `ps -o rss= -p #{$$}`
	    end

	Before:

	    23264
	    33600
	    42672
	    52160
	    61600
	    71728
	    81056
	    90528
	    100560
	    109840

	After:

	    14752
	    14816
	    15584
	    15584
	    15664
	    15664
	    15664
	    15664
	    15664
	    15664
	---
	 object.c                 |  3 +--
	 test/ruby/test_shapes.rb | 13 +++++++++++++
	 2 files changed, 14 insertions(+), 2 deletions(-)

1 files changed, 13 insertions, 0 deletions

diff --git a/test/ruby/test_shapes.rb b/test/ruby/test_shapes.rb
index 885b762eb9..ee99fbad6d 100644
--- a/test/ruby/test_shapes.rb
+++ b/test/ruby/test_shapes.rb
@@ -942,6 +942,19 @@ class TestShapes < Test::Unit::TestCase
     assert_shape_equal(RubyVM::Shape.of(obj), RubyVM::Shape.of(obj2))
   end
 
+  def test_duplicating_too_complex_objects_memory_leak
+    assert_no_memory_leak([], "#{<<~'begin;'}", "#{<<~'end;'}", "[Bug #20162]", rss: true)
+      RubyVM::Shape.exhaust_shapes
+
+      o = Object.new
+      o.instance_variable_set(:@a, 0)
+    begin;
+      1_000_000.times do
+        o.dup
+      end
+    end;
+  end
+
   def test_freezing_and_duplicating_object
     obj = Object.new.freeze
     obj2 = obj.dup