An example showing how to convert a Proc into a lambda with Fiddle

proc_to_lambda.rb

require 'fiddle'

module ProcToLambda
  WORD = Fiddle::SIZEOF_VOIDP
  RPROC = 4 * WORD
  OFFSET = 32
  VALUE = 2

  refine Proc do
    def to_lambda
      return self if lambda?

      addr = Fiddle.dlwrap(self).to_i
      ptr = Fiddle::Pointer
        .new(addr + RPROC, WORD)
        .to_str
        .unpack1('Q')

      rproc = Fiddle::Pointer.new(ptr, OFFSET + WORD)
      rproc[OFFSET, WORD] = [VALUE].pack('Q')

      self
    end
  end
end

using ProcToLambda

proc {}.to_lambda.lambda?
#=> true