path: root/transect/compiler5

== Goal

A memory-safe language with a simple translator to x86 that can be feasibly written in x86.

== Definitions of terms

Memory-safe: it should be impossible to:
  a) create a pointer out of arbitrary data, or
  b) to access heap memory after it's been freed.

Simple: do all the work in a 2-pass translator:
  Pass 1: check each instruction's types in isolation.
  Pass 2: emit code for each instruction in isolation.

== types

int
char
(address _ t), t ∋ {stack, heap, global}
(array _ t), t ∋ {stack, heap, global}

stack addresses can't be copied to heap or global
heap addresses can't be copied [1]
global addresses you're free to use anywhere

[1] (address _ heap) can't be copied or stored, can't be part of a type or
choice. Only thing you can do with it is access it from the register you wrote
it to. And even that not past a call instruction. Important detail: `free()`
is a call. So an address to something on the heap can never be invalid if the
program type-checks.

<reg x> : (address T m) <- advance <reg/mem> : (array T m), <reg offset> : (index T)