[ruby-core:119738] [Ruby master Bug#20868] Method#hash changes after compaction

[ruby-core:119738] [Ruby master Bug#20868] Method#hash changes after compaction

[peterzhu2118 (Peter Zhu) via ruby-core]

Issue #20868 has been reported by peterzhu2118 (Peter Zhu).

----------------------------------------
Bug #20868: Method#hash changes after compaction
https://bugs.ruby-lang.org/issues/20868

* Author: peterzhu2118 (Peter Zhu)
* Status: Open
* Backport: 3.1: UNKNOWN, 3.2: REQUIRED, 3.3: REQUIRED
----------------------------------------
Fix: https://github.com/ruby/ruby/pull/12004

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

For example:

```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

puts get_hash # => 2993401401091578131

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

puts get_hash # => -2162775864511574135
```



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[ruby-core:119870] [Ruby master Bug#20868] Method#hash changes after compaction

[nagachika (Tomoyuki Chikanaga) via ruby-core]

Issue #20868 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 3.1: WONTFIX, 3.2: REQUIRED, 3.3: REQUIRED to 3.1: WONTFIX, 3.2: DONE, 3.3: REQUIRED

ruby_3_2 commit:ee3428aa0e3a11ed1574b7d99222f6f08737f818 merged revision(s) commit:56ecc243e230e8e99761ec0ffc5116601f094bb0.

----------------------------------------
Bug #20868: Method#hash changes after compaction
https://bugs.ruby-lang.org/issues/20868#change-110561

* Author: peterzhu2118 (Peter Zhu)
* Status: Closed
* Backport: 3.1: WONTFIX, 3.2: DONE, 3.3: REQUIRED
----------------------------------------
Fix: https://github.com/ruby/ruby/pull/12004

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

For example:

```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

puts get_hash # => 2993401401091578131

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

puts get_hash # => -2162775864511574135
```



-- 
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 ______________________________________________
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[ruby-core:120676] [Ruby master Bug#20868] Method#hash changes after compaction

[k0kubun (Takashi Kokubun) via ruby-core]

Issue #20868 has been updated by k0kubun (Takashi Kokubun).

Backport changed from 3.1: WONTFIX, 3.2: DONE, 3.3: REQUIRED to 3.1: WONTFIX, 3.2: DONE, 3.3: DONE

ruby_3_3 commit:42f043c1893b320b9d2a38ec3b1065dee71ce863 merged revision(s) commit:56ecc243e230e8e99761ec0ffc5116601f094bb0.

----------------------------------------
Bug #20868: Method#hash changes after compaction
https://bugs.ruby-lang.org/issues/20868#change-111499

* Author: peterzhu2118 (Peter Zhu)
* Status: Closed
* Backport: 3.1: WONTFIX, 3.2: DONE, 3.3: DONE
----------------------------------------
Fix: https://github.com/ruby/ruby/pull/12004

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

For example:

```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

puts get_hash # => 2993401401091578131

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

puts get_hash # => -2162775864511574135
```



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