FAQ Object Model

FAQ about Factor's object model

How does Factor figure out the size of a tagged pointer?

First it dereferences that pointer and follows it. The first cell it points to is the object header. The lower four bits of that cell is the type tag of the object. See the functions object::base_size and object::size in vm/slot_visitor.hpp.

What is a cell?

A cell is a uintptr_t, an int the same size as a machine pointer.