What is it?

The Amsterdam Compiler Kit is a venerable piece of software that dates back to the early 1980s. It was originally written by Andrew Tanenbaum and Ceriel Jacobs as a commercial product; for many years it was also used as Minix’ native toolchain. After eventually failing as a commercial project, it was made open source under a BSD license in 2003 when it looked like it was going to be abandoned and the code lost.

The ACK contains compilers for ANSI C, K&R C, Pascal, Modula-2, Occam 1, and a primitive Basic. It contains code generators for a large number of architectures, mostly 8 and 16 bit machines; there are also a set of generic optimisation, linker and librarian tools. Each language comes with its own runtime, so if you’re a C programmer you also get a libc. Compared to gcc, it is far smaller, faster and easier to port.

This project currently hosts two versions of the ACK.

• ACK 5.6 is an incremental update of Vrije Universiteit’s last release. This has had minimum fixes necessary to make it run on modern Linux machines; unfortunately, the build system is designed for the Unixes of yesteryear and is not really up to modern standards. This version is the most complete, but is probably not particularly useful as very few of the platforms it targets exist any more. This version is provided for reference and archival purposes and to provide a backup if the 6.0 release should fail.

• ACK 6.0 is a ground-up reworking of the whole compiler suite, with a lot of the more archaic features removed. It is intended to produce a modern compiler toolchain with which actually useful work can be done, and is where all the new development happens. Currently, not all of 5.6’s features have been ported, but those that have work considerably more reliably.

What architectures does it support?

It contains assembler and linker support for: 6500, 6800, 6805, 6809, ARM, i80, Z80, Z8000, i86, i386, 68000, 68020, NS32016, S2650, SPARC, VAX, PDP11 and VideoCore IV.

It contains code generator support for: 6500, ARM, i80, Z80, Z8000, i86, i386, 68000, 68020, NS32016, SPARC, VAX4, PDP11 and VideoCore IV.

It supports these platforms: pc86, linux386, linux68k, linuxppc, linuxmips, cpm, rpi (VideoCore IV), pdpv7, msdos86 and msdos386.

However, that doesn’t necessarily mean that the code is working. There is a lot of half-finished code in the repository. There is tested support for: i86, i386, 68000, i80, and VideoCore IV.

If you’re interested in one of the other architectures, please ask on the mailing list. Some code archaeology will be required to enable a new target.

What’s the generated code quality like?

Honestly? Not great.

The ACK was designed in an era when processor were CISC memory-centric architectures with very small numbers of registers. For these architectures, it produces middling good results, although modern compilers do far better (at the expense of being enormously larger and more complex).

However, for register-centric architectures, it’s pretty much a dead loss. The register allocator cannot make effective use of large numbers of registers and the underlying architecture requires nearly all operations to touch memory. It is very easy to port to a new architecture… but the generated code is terrible.

I, dtrg, cannot honestly recommend using the ACK for production code on modern architectures unless as a stop-gap measure or unless the other benefits of the ACK (e.g. having a very lightweight turnkey toolchain is valuable to you) outweigh the code quality.

Haven’t I seen this before somewhere?

Quite likely. The ACK has been used as the standard Minix compiler for years. While the ACK was still commercial, this was done by distributing binaries; when it get opened, a version was forked off and is now used as part of the Minix base build. You can find Minix’s version here. This is an extremely stripped down variant that supports only the Minix platform on the i386 and i86 architectures and was done by Michael Kennett.

In addition, the original 5.5 release is still available on the Vrije Universiteit ACK page.

There may also be other versions elsewhere. The ACK is BSD licensed and as a result if people want to fork the codebase and use it elsewhere, they don’t even need to ask, or indeed tell anyone. If you know of any other uses of the compiler, please let me (dtrg) know — I’d like to put in a link.

What’s the involvement of Andrew Tanenbaum, Ceriel Jacobs and Vrije Universiteit?

They have no official involvement.

They’re aware that I, dtrg, am doing this, and are quite happy with it and maintain an interest, but are not actively participating in the project. (Due to being busy people with other things to do.) I, dtrg, have nothing to do with Vrije Universiteit and have never even been to the Netherlands.