[ruby-core:113345] [Ruby master Bug#19611] Ruby hangs up with `while true && true`

Issue #19611 has been updated by kjtsanaktsidis (KJ Tsanaktsidis).


Hm, interesting - it falls into an infinite loop in `iseq_peephole_optimize`, because it's doing useless jump elimination on labels that recursively point to each other.

At the beginning of `iseq_peephole_optimize`, the instruction sequence of your `hoge` method looks like this:

```
-- raw disasm--------
  0000 jump                 <L000>                                      (   2)
<L004> [sp: -1]
  0002 putnil                                                           (   2)
<L005> [sp: -1]
  0003 pop                                                              (   2)
  0004 jump                 <L000>                                      (   2)
<L001> [sp: -1]
<L000> [sp: -1]
  0006 jump                 <L006>                                      (   2)
<L006> [sp: -1]
  0008 jump                 <L001>                                      (   2)
<L003> [sp: -1]
  adjust: [label: 4]
  0010 putnil                                                           (   2)
<L002> [sp: -1]
  trace: 10
  0011 leave                                                            (   4)
---------------------
```

Looks like the peephole optimizer is continuously changing that first jump to point to L006, then L001, then L006 again, forever.

This PR should fix it I think: https://github.com/ruby/ruby/pull/7760

----------------------------------------
Bug #19611: Ruby hangs up with `while true && true`
https://bugs.ruby-lang.org/issues/19611#change-102905

* Author: tompng (tomoya ishida)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0 (2022-12-25 revision a528908271) +YJIT [x86_64-darwin20]
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
Fails to run this code. It hangs up. Ctrl+C does not work.
~~~ruby
def hoge
  while true && true
  end
end
~~~

Compiling `while true && true; end` will also hangs up
~~~ruby
irb(main):001:0> RubyVM::InstructionSequence.compile 'while true && true; end'; puts :done
(no response)
~~~



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