SystemStackError passing value back to Ruby

[JasonBarnabe]

require 'mini_racer'
context = MiniRacer::Context.new(timeout: 500, max_memory: 20_000_000)
context.attach 'greasyforkSetLogger', ->(value) {}
context.eval(File.read('script.js'))

script.js

Traceback (most recent call last):
       11: from /home/jason/.rbenv/versions/2.6.2/bin/irb:23:in `<main>'
       10: from /home/jason/.rbenv/versions/2.6.2/bin/irb:23:in `load'
        9: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
        8: from (irb):4
        7: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:198:in `eval'
        6: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:198:in `synchronize'
        5: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:200:in `block in eval'
        4: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:307:in `timeout'
        3: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `block (2 levels) in eval'
        2: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `eval_unsafe'
        1: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `new'
SystemStackError (stack level too deep)

If you change greasyforkSetLogger(val); to pass a literal string, there's no error. Something to do with converting the JS object into Ruby?

[SamSaffron]

What is the minimal repro, can you condense it a bit?

[JasonBarnabe]

a = {}
a.foo = a
a.bar = new Proxy(function() {}, {
  set: function(obj, prop, val) {
    greasyforkSetLogger(val);
    return true;
  }
});
a.bar.baz = a

Traceback (most recent call last):
	6: from script.rb:4:in `<main>'
	5: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:198:in `eval'
	4: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:198:in `synchronize'
	3: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:200:in `block in eval'
	2: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:307:in `timeout'
	1: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `block (2 levels) in eval'
/home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `eval_unsafe': stack level too deep (SystemStackError)

#
# Fatal error in v8::Isolate::Dispose()
# Disposing the isolate that is entered by a thread.
#

script.rb: [BUG] Illegal instruction at 0x00007f20feed9f72
ruby 2.6.2p47 (2019-03-13 revision 67232) [x86_64-linux]

-- Control frame information -----------------------------------------------
c:0001 p:0000 s:0003 E:000c00 (none) [FINISH]


-- Machine register context ------------------------------------------------
 RIP: 0x00007f20feed9f72 RBP: 0x00007ffe75054960 RSP: 0x00007ffe75054948
 RAX: 0x0000000000000063 RBX: 0x0000558f69148f00 RCX: 0x0000000000000000
 RDX: 0x00007f2102366b80 RDI: 0x00007ffe75052190 RSI: 0x0000000000000000
  R8: 0x0000000000000063  R9: 0x0000000000000063 R10: 0x00007f20fe646a9f
 R11: 0x00007f20feed9f60 R12: 0x0000558f691002f0 R13: 0x0000558f69140fb0
 R14: 0x00007ffe750549b0 R15: 0x0000558f69148f00 EFL: 0x0000000000010202

-- C level backtrace information -------------------------------------------
SEGV received in ILL handler
Aborted (core dumped)

If I don't pass back to Ruby...

a = {}
a.foo = a
a.bar = new Proxy(function() {}, {
  set: function(obj, prop, val) {
    return true;
  }
});
a.bar.baz = a

Traceback (most recent call last):
	7: from script.rb:4:in `<main>'
	6: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:198:in `eval'
	5: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:198:in `synchronize'
	4: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:200:in `block in eval'
	3: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:307:in `timeout'
	2: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `block (2 levels) in eval'
	1: from /home/jason/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/mini_racer-0.2.9/lib/mini_racer.rb:201:in `eval_unsafe'
JavaScript at JSON.stringify (<anonymous>): TypeError: Converting circular structure to JSON (MiniRacer::RuntimeError)

[JasonBarnabe]

Even more condensed:

a = {}
a.foo = a
greasyforkSetLogger(a)