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Created: Friday, December 25 2009 13:45.13 CST

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Code release: C-subset compiler in Objective Caml

Author: RolfRolles

# Views: 7786

Here is the source code for a compiler that I wrote in Objective Caml this semester, for a subset of the C language.  It requires a standalone C->IR translator which is not included in this release, as the school owns the copyright on that particular piece of code.  Hence one cannot immediately use this compiler to compile C programs without writing a C front end; anyway, an existing compiler such as MSVC or GCC would be a better choice.

The portion of the code that I wrote (everything except bitv.ml and .mli) totals roughly 3200 lines of code.  It includes two optimizations based on classical data-flow analysis, constant propagation and dead-statement elimination.  It also supports translation into and out of static single assignment form, as well as two optimizations based on SSA:  constant propagation and loop-invariant code motion.  The code for the graph-coloring register allocator is not included.  As a back-end, the compiler produces C code that can be compiled by any other C compiler.

The code is a pretty good example of how to structure medium-sized programs in functional programming languages.  I tried to adopt a pure functional style throughout most of the codebase.  Sometimes this failed:  cfg_ir.ml is unnecessarily ugly, and should have been re-written in an imperative style with mutability; also, I made the mistake of using a mutable array to describe Phi values in static single assignment whereas pure functional style would have dictated a list.  But those are my only complaints with the code; overall, I'm pretty pleased with how it all turned out.

This code is substantially more sophisticated than the compiler that I wrote to break VMProtect, so if you can read and understand this release, you should be in good shape for breaking virtualization obfuscators.

Blog Comments

qaysel	Posted: Sunday, January 3 2010 19:37.12 CST
Thanks, it's very interesting and educational to me. I got it to build after installing ocamlgraph and fudging a bit with the Makefile. The source is quite readable, and with the sample code at http://txt.pastebin.com/f13254815 I'm able to understand the IR syntax. Thanks again.

RolfRolles	Posted: Tuesday, January 5 2010 15:19.49 CST
Good point -- I have re-uploaded the package and included an "ir" directory with a collection of samples of C->IR translations. Thanks.

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