"WeakMap key can't be an instance of Integer" breaks google-protobuf 3.15

[ivoanjo]

Hello there! 👋

I've been running a few experiments trying to run ddtrace with TruffleRuby.

I found an incompatibility that breaks the latest google-protobuf gem.

Example:

require 'bundler/inline'

puts RUBY_DESCRIPTION

gemfile do
  source 'https://rubygems.org'

  gem 'google-protobuf', '= 3.15.1'
end

require 'google/protobuf'

output on TruffleRuby:

truffleruby 21.0.0.2, like ruby 2.7.2, GraalVM CE Native [x86_64-darwin]
<internal:core> core/weakmap.rb:27:in `check_key_or_value': WeakMap key can't be an instance of Integer (ArgumentError)
	from <internal:core> core/weakmap.rb:34:in `[]='
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/truffle/truffle/cext.rb:847:in `rb_funcall'
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/ext/google/protobuf_c/protobuf.c:286:in `ObjectCache_Add'
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/ext/google/protobuf_c/defs.c:298:in `DescriptorPool_alloc'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/truffle/truffle/cext.rb:1184:in `__allocate__'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/truffle/truffle/cext.rb:1131:in `new'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/truffle/truffle/cext.rb:1131:in `rb_class_new_instance'
	from class.c:67:in `rb_class_new_instance'
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/ext/google/protobuf_c/defs.c:372:in `Defs_register'
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/ext/google/protobuf_c/protobuf.c:384:in `Init_protobuf_c'
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/lib/google/protobuf.rb:51:in `gem_original_require'
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/lib/google/protobuf.rb:51:in `<top (required)>'
	from <internal:core> core/kernel.rb:234:in `gem_original_require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:88:in `block in require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:58:in `each'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:58:in `require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/inline.rb:70:in `block in gemfile'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/settings.rb:124:in `temporary'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/inline.rb:54:in `gemfile'
	from repro-protobuf.rb:5:in `<main>'
<internal:core> core/kernel.rb:236:in `gem_original_require': cannot load such file -- google/2.7/protobuf_c (LoadError)
	from /Users/ivo.anjo/.rvm/gems/truffleruby-21.0.0.2/gems/google-protobuf-3.15.1/lib/google/protobuf.rb:49:in `<top (required)>'
	from <internal:core> core/kernel.rb:234:in `gem_original_require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:88:in `block in require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:58:in `each'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:58:in `require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/inline.rb:70:in `block in gemfile'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/settings.rb:124:in `temporary'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/inline.rb:54:in `gemfile'
	from repro-protobuf.rb:5:in `<main>'
<internal:core> core/kernel.rb:236:in `gem_original_require': cannot load such file -- google-protobuf (LoadError)
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:74:in `block (2 levels) in require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:69:in `each'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:69:in `block in require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:58:in `each'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/runtime.rb:58:in `require'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/inline.rb:70:in `block in gemfile'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/settings.rb:124:in `temporary'
	from /Users/ivo.anjo/.rvm/rubies/truffleruby-21.0.0.2/lib/mri/bundler/inline.rb:54:in `gemfile'
	from repro-protobuf.rb:5:in `<main>'

It looks like MRI allows numbers as keys in WeakMap, but TruffleRuby doesn't:

$ ruby -e "puts RUBY_DESCRIPTION; require 'objspace'; ObjectSpace::WeakMap.new.tap { |it| it[0] = 'boom' }"
truffleruby 21.0.0.2, like ruby 2.7.2, GraalVM CE Native [x86_64-darwin]
<internal:core> core/weakmap.rb:27:in `check_key_or_value': WeakMap key can't be an instance of Integer (ArgumentError)
	from <internal:core> core/weakmap.rb:34:in `[]='
	from -e:1:in `block in <main>'
	from <internal:core> core/kernel.rb:532:in `tap'
	from -e:1:in `<main>'

As usual, let me know if I can provide any more info :)

P.s.: google-protobuf = 3.14.0 seems to work fine so I'm using that as a workaround for now. The google-protobuf changes were done as part of protocolbuffers/protobuf#8184 .

[eregon]

Thanks for the great report!

Right, this is a change from Ruby 2.7.

CRuby 2.6 also disallowed such keys:

$ ruby -ve "require 'objspace'; ObjectSpace::WeakMap.new.tap { |it| it[0] = 'boom' }"                  
ruby 2.6.6p146 (2020-03-31 revision 67876) [x86_64-linux]
Traceback (most recent call last):
	3: from -e:1:in `<main>'
	2: from -e:1:in `tap'
	1: from -e:1:in `block in <main>'
-e:1:in `[]=': cannot define finalizer for Integer (ArgumentError)

It's unclear why the example with the inline Gemfile does not fail on CRuby 2.6.6 though.

[eregon]

Ah, this is why it works on CRuby 2.6:
https://github.com/protocolbuffers/protobuf/blob/052dc799d24a2d27d847e6bad78019364e1b188f/ruby/ext/google/protobuf_c/protobuf.c#L212-L221
https://github.com/protocolbuffers/protobuf/blob/052dc799d24a2d27d847e6bad78019364e1b188f/ruby/ext/google/protobuf_c/protobuf.c#L262-L265

@norswap Could you look into this?
In this case it's a an Integer key, coming from https://github.com/protocolbuffers/protobuf/blob/052dc799d24a2d27d847e6bad78019364e1b188f/ruby/ext/google/protobuf_c/protobuf.c#L228

[chrisseaton]

This blocks us from using a newer grpc as well.

[norswap]

I just started looking into it, I think it should be an easy fix.

[norswap]

Well, not that easy :)
Fixed in 1a40956