Question

I recently discover the LLVM (low level virtual machine) project, and from what I have heard It can be used to performed static analysis on a source code. I would like to know if it is possible to extract the different function call through function pointer (find the caller function and the callee function) in a program.

I could find the kind of information in the website so it would be really helpful if you could tell me if such an library already exist in LLVM or can you point me to the good direction on how to build it myself (existing source code, reference, tutorial, example…).

EDIT:

With my analysis I actually want to extract caller/callee function call. In the case of a function pointer, I would like to return a set of possible callee. both caller and callee must be define in the source code (this does not include third party function in a library).

Answer 1

You should take a look at Elsa. It is relatively easy to extend and lets you parse an AST fairly easily. It handles all of the parsing, lexing and AST generation and then lets you traverse the tree using the Visitor pattern.

class CallGraphGenerator : public ASTVisitor
{
  //...
  virtual bool visitFunction(Function *func);
  virtual bool visitExpression(Expression *expr);
}

You can then detect function declarations, and probably detect function pointer usage. Finally you could check the function pointers’ declarations and generate a list of the declared functions that could have been called using that pointer.