instance_sizeof expression returns an
Int32 with the instance size of a given class. For example:
class Point def initialize(@x, @y) end end Point.new 1, 2 # 2 x Int32 = 2 x 4 = 8 instance_sizeof(Point) # => 12
Even though the instance has two
Int32 fields, the compiler always includes an extra
Int32 field for the type id of the object. That's why the instance size ends up being 12 and not 8.