For teaching purpose we are building a javascript step by step interpreter for (a subset of) C code.
Basically we have : int,float..., arrays, functions, for, while... no pointers. The javascript interpreter is done and allow us to explain how a boolean expression is evaluated, will show the variables stack...
For now, we are manually converting our C examples to some javascript that will run and build a stack of actions (affectation, function call...) that can later on be used to do the step by step stuff. Since we are limiting ourselves to a subset of C it's quite easy to do.
Now we would like to compile the C code to our javascript representation. All we need is a Abstract-syntax tree of the C code and the javascript generation is straightforward.
Do you know a good C-parser that could generate a such tree ? No need to be in javascript (but that would be perfect), any language is alright as this can be done offline.
I've looked at Emscripten ( https://github.com/kripken/emscripten ) but it's more a C=>javascript compiler and that's not what we want.
I've recently used Eli Bendersky's pycparser to mess with ASTs of C code. I think it'd work well for your purposes.