In order to continue my dive into reading real code, I'd like to read and understand the source code of an actual in-use compiler. Is there one that you think is particularly well-written, elegant, and perhaps, still relatively small? Any suggestions? Any experiences?
Resolution: I've decided to read the Lua source code. I've been bookmarking (the few) resources available to help reading and understanding the Lua code.
GCC is opensource so by definition you can read its source http://gcc.gnu.org/ and it is highly used.
And it supports: C, C++, Objective-C, Fortran, Java, and Ada
Lua is compact and has very good performance for a byte-code compiler. The language is simple but powerful, and does many things right: lexical scoping, closures, gc, etc. There is also a jit version once you are ready for more performance.
Though the compiler and runtime source code are not designed as a teaching vehicle, it is quite clean, and the language and its development are well documented.
I most highly recommend A Retargetable C Compiler: Design and Implementation by Chris Fraser and Dave Hanson. It describes lcc, a production-quality C89 compiler that was heavily used from its release in the early 1990s to the release of the c99 standard. These two guys are masters of their craft, and they spent 10 years working on a compiler that they could use as a research and teaching tool.
There are lots of simpler compilers out there but none that is better designed, and none that is as well documented.
It is unfortunate that the compiler itself is written in C. I once asked Hanson, "So you and Chris have spent ten years on this incredibly carefully crafted compiler, and now it is finally published as a book. What did you learn?" His response: "C is a lousy language to write a compiler in."
I couldn't agree more.
You might want to consider Ruby as an alternative. You can download the source code from http://www.ruby-lang.org/en/downloads/.
I would highly recommend this book:
http://www.amazon.com/Scripting-Mastery-Premier-Press-Development/dp/1931841578
The code is in C, but if you are a current programmer you should be able to catch on quickly. It not only goes over the complete creation of a procedural compiler, assembler and virtual machine - it will explain the theory involved in all steps. You will get a much better understanding of everything from how compilers compile and Annalise code to how the CPU and memory run it. In fact, you build a VM (virtual memory/virtual processor/excettra) during the book.
I could not give a higher recommendation for you considering your interest into how the computer compiles and runs code.
You can download the source to the D programming language compiler (front end) at digitalmars