From 6e1eeeebfb453fa7c871869c19375ce60fbd7413 Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Sat, 27 Jul 2019 16:01:55 -0700 Subject: 5485 - promote SubX to top-level --- archive/3.transect/compiler5 | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 archive/3.transect/compiler5 (limited to 'archive/3.transect/compiler5') diff --git a/archive/3.transect/compiler5 b/archive/3.transect/compiler5 new file mode 100644 index 00000000..aeb857f4 --- /dev/null +++ b/archive/3.transect/compiler5 @@ -0,0 +1,32 @@ +== 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. + + : (address T m) <- advance : (array T m), : (index T) -- cgit 1.4.1-2-gfad0