What is a runtime system (Overview).

Posted on May 22, 2015

This post is aimed at total beginners. Especially those who have no idea what a runtime system is and is a gross oversimplification. :) Let’s go. Later I will write something about the haskell runtime system.

This post was inspired by The GHC Runtime System by Edward Z. Yang (2013) and A Runtime System by Andrew W. Appel (1989). I also tried reading: The Implementation of Functional Programming Languages by Simon Peyton Jones, published by Prentice Hall, 1987. and Implementing functional languages: a tutorial by Simon Peyton Jones and David Lester. Published by Prentice Hall, 1992. but they’re really big and quite dated. You may also read wikipedia on runtime systems.

So what is a runtime system? It is a program that is invoked by the compiler to wrap your compiled program/code and gives it bindings to the “API” provided by the environment(operating system) that the program is running in. So the runtime system can’t run on it’s own. It only runs when the program, for example a haskell program, is running and as you would expect the runtime system would vary between operating systems because the environments are different.

It provides primitive langauge features unlike a standard library which is typically implemented in the language itself.

We count on the runtime system to provide the following services among others:

Haskell runtime system.

Haskell features that complicate the design of the runtime system:

However, emphasis on pure computation simplifies the design of the garbage collector and Software Transactional Memory.

GHC and the haskell runtime system.

GHC is broken down into three parts.

As you can see the runtime system is developed as part of GHC but not part of the compiler itself.


I can’t keep this on without turning these into notes I wrote down when reading a paper. So I’ll write a different and more specific post later.