allocation_map.rb

#   Ruby has #source_location method that returns code location where a method was declared.
# What Ruby lacks is alike functionality that could show where an object was created.
# Below is a very rough solution that may help with tracing object allocations
# by storing the first entry in the caller list during object initialization phase.
# It doesn't work for built-in classes like Fixnum and for classes that don't invoke #initialize()
# like the ones derived from ActiveRecord::Base, but can be potentially tailored to address
# at least the latter case by overriding ActiveRecord::Base.new in addition to overriding #initialize()

class BasicObject
  attr_reader :allocated_at

  def initialize_with_allocated_at(*options)
    unless @allocated_at
      @allocated_at = caller.first
      return initialize_without_allocated_at(*options)
    end
  end

  def self.enable_allocated_at
    self.send :alias_method, :initialize_without_allocated_at, :initialize
    self.send :alias_method, :initialize, :initialize_with_allocated_at
  end
end

ObjectSpace.each_object(Class) do |klass|
  klass.enable_allocated_at
end

class Object

  # Call this method to get a hash where
  # keys are strings representing locations in the source code
  # and values are objects allocated at these locations
  #
  # Example:
  #   allocation_map(Person) # only show places where Person.new was called
  #         or
  #   allocation_map() # beware, this may return A LOT of objects
  #
  def allocation_map(*each_object_options)
    ObjectSpace.each_object(*each_object_options).reduce({}) { |hash, object|
      hash[object.allocated_at] ||= []
      hash[object.allocated_at] << object if object.respond_to?(:allocated_at)
      hash
    }
  end
end