Ruby 强制垃圾收集未按预期工作

Question

在下面的代码中：

class ExampleClass
  def initialize
    ObjectSpace.define_finalizer(self, proc{puts 'dead'})
  end
end

ex = ExampleClass.new
ex = nil

GC.start

while true
  # the while loop is to prevent the program from terminate
  # if the program does terminate, the finalizer gets called in the end like expected
end

此处的终结器从未被调用，也没有输出。我本来希望垃圾收集器收集 ex 因为它已被取消引用。为什么 GC.start 不强制收集 ex 并立即导致 finalizer to be called？

Answer 1

我相信当你创建一个新的Proc (proc just calls Proc.new, in Kernel)

Creates a new Proc object, bound to the current context.

意味着它正在保存对 self 对象的引用，因此永远不会被垃圾收集器取消引用以收集它。您应该在 class 方法中创建 proc，这样上下文就变成 class 而不是您要销毁的实例。

class ExampleClass
  def initialize
    ObjectSpace.define_finalizer(self, self.class.finalize)
  end

  def self.finalize
    proc { puts "dead" }
  end

end


ex = ExampleClass.new
# needed to do something with the object as well, not sure why,
# but it won't work without this line either
puts "object id = #{ex.object_id}"
ex = nil

GC.start
while true
end

这输出

object id = 70223915005060
dead
^Cexample.rb:20:in `<main>': Interrupt

Ruby 强制垃圾收集未按预期工作

Ruby forcing garbage collection not working as expected

ruby

garbage-collection

finalizer