From 42f043c1893b320b9d2a38ec3b1065dee71ce863 Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashikkbn@gmail.com>
Date: Tue, 14 Jan 2025 17:40:39 -0800
Subject: [PATCH] merge revision(s) 56ecc243e230e8e99761ec0ffc5116601f094bb0:
 [Backport #20868]

	[Bug #20868] Fix Method#hash to not change after compaction

	The hash value of a Method must remain constant after a compaction, otherwise
	it may not work as the key in a hash table.

	For example:

	    def a; end

	    # Need this method here because otherwise the iseq may be on the C stack
	    # which would get pinned and not move during compaction
	    def get_hash
	      method(:a).hash
	    end

	    puts get_hash # => 2993401401091578131

	    GC.verify_compaction_references(expand_heap: true, toward: :empty)

	    puts get_hash # => -2162775864511574135
---
 test/ruby/test_method.rb | 21 +++++++++++++++++++++
 version.h                |  2 +-
 vm_method.c              |  2 +-
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/test/ruby/test_method.rb b/test/ruby/test_method.rb
index 423ebd391a..1a3e6fb5b7 100644
--- a/test/ruby/test_method.rb
+++ b/test/ruby/test_method.rb
@@ -209,6 +209,27 @@ class TestMethod < Test::Unit::TestCase
     assert_kind_of(String, o.method(:foo).hash.to_s)
   end
 
+  def test_hash_does_not_change_after_compaction
+    omit "compaction is not supported on this platform" unless GC.respond_to?(:compact)
+
+    # iseq backed method
+    assert_separately([], <<~RUBY)
+      def a; end
+
+      # Need this method here because otherwise the iseq may be on the C stack
+      # which would get pinned and not move during compaction
+      def get_hash
+        method(:a).hash
+      end
+
+      hash = get_hash
+
+      GC.verify_compaction_references(expand_heap: true, toward: :empty)
+
+      assert_equal(hash, get_hash)
+    RUBY
+  end
+
   def test_owner
     c = Class.new do
       def foo; end
diff --git a/version.h b/version.h
index 89ede160c7..e8f5ba6e1b 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 6
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 109
+#define RUBY_PATCHLEVEL 110
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"
diff --git a/vm_method.c b/vm_method.c
index 232ba03e61..7b57b56cd6 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -2237,7 +2237,7 @@ rb_hash_method_definition(st_index_t hash, const rb_method_definition_t *def)
 
     switch (def->type) {
       case VM_METHOD_TYPE_ISEQ:
-        return rb_hash_uint(hash, (st_index_t)def->body.iseq.iseqptr);
+        return rb_hash_uint(hash, (st_index_t)def->body.iseq.iseqptr->body);
       case VM_METHOD_TYPE_CFUNC:
         hash = rb_hash_uint(hash, (st_index_t)def->body.cfunc.func);
         return rb_hash_uint(hash, def->body.cfunc.argc);