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Mon Jan 16 10:04:55 EST 2012

Language.C.Analysis

Goal: get at all (packed) struct definitions to generate Lua tables
for translating between binary storage and table representation.

Where to start in [1]?  I'm looking at the source, and the first thing
that looks familiar is this from AstAnalysis.hs :

  analyseAST :: (MonadTrav m) => CTranslUnit -> m GlobalDecls

This uses MonadTrav[2] class.  A predefined instance of this is
Trav[3], which is parameterized by a user state.

For now I'm using this, inside the IO monad for getting at the file
system.

  info  :: (CTranslUnit -> b) -> IO b
  decls :: IO (Trav () GlobalDecls)

  decls = info analyseAST

Here info parses a C file from the file system into CTranslUnit using
readFile, parseC, initPos and decls is the output of the analysis
using a Trav monad without user state.

So this gives C file to GlobalDecls[4] dat structure.


  GlobalDecls	 
     gObjs :: Map Ident IdentDecl
     gTags :: Map SUERef TagDef
     gTypeDefs :: Map Ident TypeDef

Getting at the keys of gObjs and gTypeDefs:


  decls tu = fst ds where
    Right ds = runTrav_ $ analyseAST tu
  objIdents     = keys . gObjs     . decls
  typeDefIdents = keys . gTypeDefs . decls

These don't seem to have structure definitions.  That because they are
in SUERef[5], which names anonymous types.

  tagSUErefs    = keys . gTags     . decls

As a list of strings:

  onFile ((Prelude.map show) . tagSUErefs)

Next: write a function that filters out all packed structures.

That was relatively straightforward.  However, trying to actually map
that data to something exportable (size + basic data types like int /
float) actually requires evaluation of C code in the most general
case.  So solving the problem in a generic way seems quite a hassle.

Practically I run into initializations through enums, which show up as
CVar.  This probably needs access to a global symbol table.

It does give me the impression that for many C analysis tasks, a C
parser is not enough.  An interpretation step is necessary, which can
probably best be left to a C compiler!

So: almost there.  More after the break :)

[1] http://hackage.haskell.org/packages/archive/language-c/0.4.2/doc/html/Language-C-Analysis.html
[2] http://hackage.haskell.org/packages/archive/language-c/0.4.2/doc/html/Language-C-Analysis-TravMonad.html
[3] http://hackage.haskell.org/packages/archive/language-c/0.4.2/doc/html/Language-C-Analysis-TravMonad.html#t:Trav
[4] http://hackage.haskell.org/packages/archive/language-c/0.4.2/doc/html/Language-C-Analysis-SemRep.html#t:GlobalDecls
[5] http://hackage.haskell.org/packages/archive/language-c/0.4.2/doc/html/Language-C-Data-Ident.html#t:SUERef


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