The Basic Compiler RecipeĪlthough you should already pretty much know this, a compiler is really a grouping of three to four components (there are some more sub-components) where data is fed from one to the next in a pipeline fashion. To understand completely everything might take a little longer, but you should be able to run through all of this stuff (and hopefully understand a good amount of it) in an afternoon. Of course, this will be a “follow me” kind of deal, so it should be much shorter for you. What we will be building took me about 3 days of toying with, but I have a few failed attempts under my belt and those do have impact on my comprehension. We will also use a lot of tools to abstract the layers of complexity and make it manageable. There is plenty of stuff going on here and it might seem scary at first, but honestly, this is about as simple as it gets. The grammar we’re dealing with is actually very tiny (~100 LOC), so it should be feasible. In addition to C, both Lex and Bison have their own syntax which may seem daunting at first, but I’ll try to explain as much as possible. LLVM is specifically C++ and our toy language will follow suit since there are some niceties of OOP and the STL (C++’s stdlib) that make for fewer lines of code. The tools we’ll be using are C/C++ based. Let’s Get Some Questions Out of the Way 1. Some of the functionality is unimplemented, so you can have the satisfaction of actually implementing some of this stuff yourself and get the hang of writing a compiler with a little help. It will support two basic types, doubles and integers. If you follow this article, you should end up with a language that can define functions, call functions, define variables, assign data to variables and perform basic math operations. The goal, of course, is to make this an easy-to-understand introductory resource for people interested but not experienced with compilers. That said, I plan on keeping this as simple as possible. I won’t be covering much theory, so if you haven’t brushed up on your BNF grammars, AST data structures and the basic compiler pipeline, I suggest you do so.
Fleex translate how to#
The goal of this article is to provide such a resource and explain in a relatively step by step manner how to create the most basic-but-functional compiler from start to “finish”. You’ve probably wanted to try this but never found the resources, or did but couldn’t quite follow. It’s more likely, however, that you’re probably interested in compilers and languages as I am, and have probably been hitting similar roadblocks.
Maybe you want to see what I’ve been doing with my time. The other thing I’ve been lucky to have in my corner this time is the help of LLVM, a tool which I’m hardly qualified to talk too much about, but it’s been quite handy in implementing most of the business end (read: complex aspects) of my toy compiler. And again, needless to say, this post is mostly inspired by my latest attempt, though this one has been much more successful (so far).įortunately over the last few years I’ve been involved in some projects that helped give me perspective and experience on what’s really involved in building a compiler. I’d usually get caught up at the semantic parsing stage.
Needless to say, I’ve tried, without much success, to write a small toy language/compiler before. A lot of the concepts of compiler design can easily go way over most programmers’ heads, even the intelligent ones. I’ve always been interested in compilers and languages, but interest only gets you so far.
Fleex translate update#
Update (March 19 2010): this article was updated for LLVM 2.6 thanks to a great patch by John Harrison.
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