Issue #8444 has been reported by jamespharaoh (James Pharaoh).

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Bug #8444: Regexp vars $~ and friends are not thread local
https://bugs.ruby-lang.org/issues/8444

Author: jamespharaoh (James Pharaoh)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: trunk
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


=begin
In the docs for the Regexp special variables, $~ and friends, it says "These global variables are thread-local and method-local variables". However the following gives an unexpected result:

  def get_proc
    proc do |str|
      str =~ /(.+)/
      sleep 0.1
      puts "got #{$1} from #{str}\n"
    end
  end
  proc = get_proc
  t1 = Thread.new { proc.call "abc" }
  t2 = Thread.new { proc.call "def" }
  t1.join
  t2.join

This outputs the following:

  got abc from abc
  got abc from def

The expected result is of course:

  got abc from abc
  got def from def

Clearly the variables are being scoped to the get_proc method and are being shared by both threads. This runs contrary to the documentation and also to expectations.

This behaviour should either be changed, or the documentation updated to reflect the actual behaviour.

Interestingly, the following does work as expected:

  proc = proc do |str|
    str =~ /(.+)/
    sleep 0.1
    puts "got #{$1} from #{str}\n"
  end
  t1 = Thread.new { proc.call "abc" }
  t2 = Thread.new { proc.call "def" }
  t1.join
  t2.join

=end


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