Back to the Future: The Story of Squeak, A Practical Smalltalk Written in Itself

Created: 2020-08-21T05:39:06.976675

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• Started from an Apple Smalltalk image.
• Interpreter is written as a single class which both runs inside the Smalltalk VM, but can also be transpiled to C.
• #become: is slow under Squeak because there is no longer an object table.
• A subset of selectors were chosen to be allowed in the interpreter class; these are the ones the translator knows how to transpile to C.
• Aside from the memory layout, the runtime is otherwise based on the Blue Book.

Object Memory

• Size of the object
• Class pointer of the object
• Hash code of the object
• Format of the object (???)

Up to ~31 objects may be declared, at VM build time, to be "compact." These use a compact 32-bit class header. Other classes use a much larger class header.