merge revision(s) 417b1a36447cb2c650de55b433ba623541fb8bb3: [Backport #19550]

	Fix memory leak for iclass

	[Bug #19550]

	If !RCLASS_EXT_EMBEDDED (e.g. 32 bit systems) then the rb_classext_t is
	allocated throug malloc so it must be freed.

	The issue can be seen in the following script:

	```
	20.times do
	  100_000.times do
	    mod = Module.new
	    Class.new do
	      include mod
	    end
	  end

	  # Output the Resident Set Size (memory usage, in KB) of the current Ruby process
	  puts `ps -o rss= -p #{$$}`
	end
	```

	Before this fix, the max RSS is 280MB, while after this change, it's
	30MB.
	---
	 gc.c                     |  2 +-
	 test/ruby/test_module.rb | 15 +++++++++++++++
	 2 files changed, 16 insertions(+), 1 deletion(-)

3 files changed, 17 insertions, 2 deletions

diff --git a/gc.c b/gc.c
index 58f793f949..9978d54cd7 100644
--- a/gc.c
+++ b/gc.c
@@ -3662,7 +3662,7 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
         cc_table_free(objspace, obj, FALSE);
         rb_class_remove_from_module_subclasses(obj);
         rb_class_remove_from_super_subclasses(obj);
-#if !USE_RVARGC
+#if !RCLASS_EXT_EMBEDDED
         xfree(RCLASS_EXT(obj));
 #endif
 
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 6c4defd6b1..54985f0f87 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -3274,6 +3274,21 @@ class TestModule < Test::Unit::TestCase
     assert_match(/::Foo$/, mod.name, '[Bug #14895]')
   end
 
+  def test_iclass_memory_leak
+    # [Bug #19550]
+    assert_no_memory_leak([], <<~PREP, <<~CODE, rss: true)
+      code = proc do
+        mod = Module.new
+        Class.new do
+          include mod
+        end
+      end
+      1_000.times(&code)
+    PREP
+      3_000_000.times(&code)
+    CODE
+  end
+
   private
 
   def assert_top_method_is_private(method)
diff --git a/version.h b/version.h
index d6ab89be3b..d1898b80ff 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 2
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 78
+#define RUBY_PATCHLEVEL 79
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"