Bug #17420
Updated by Eregon (Benoit Daloze) over 3 years ago
With an empty file `a.rb`:
```
$ ruby --disable-gems -e 'Ractor.new { puts $" }.take'
-e:1:in `block in <main>': can not access global variables $" from non-main Ractors (RuntimeError)
``` (RuntimeError)```
That is expected, given the rules for global variables.
```
ruby --disable-gems -e 'Ractor.new { require "./a.rb"; }.take; p $"'
[... , "/home/eregon/a.rb"]
```
Is it OK that the Ractor can do `require`, which does modify `$"`?
I think it's not, and it might lead to segfaults if e.g. the main Ractor mutates `$"` in parallel to some other Ractor doing `require`.
Probably `require` needs to be forbidden in non-main Ractors (it does mutate `$"`, so it's logical), or there needs to be always VM-global synchronization on any access to `$"` (otherwise, segfaults are possible).
The latter doesn't seem reasonable, especially when considering the user might do `$".each { ... }`.
---
Note that RubyGems' `require` does not work on non-main Ractors (pretty much expected given it depends on a lot of global state):
```
$ ruby -e 'Ractor.new { require "./a.rb"; }.take'
<internal:/home/eregon/prefix/ruby-master/lib/ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:37:in `require': can not access non-shareable objects in constant Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (NameError)
```
This probably also has consequences for `autoload`.
Maybe the `zeitwerk` gem can help with the mode to resolve all autoload at once.