Search C++ call graph recursively for specific functions

Question

I have a large C/C++ project where I would like to analyse the call graph for a subset of functions.

Ex for something like:

void A_Func1(){}
void A_Func2(){}

void IntermediateFunc()
{
  A_Func1();
  A_Func2();
}

void StartFunc()
{
  IntermediateFunc();
}

I would like to get the list of functions that starts with "A_" called directly or indirectly from StartFunc.

My first thought was using clang which has the CallGraph action, but the documentation is sparse and I am slowly getting to the conclusion that I cannot use it how I want.

So the question: How do I use clangs tooling libraries to perform generate such a list?

Answer 1

I find the answer from polkovnikov.ph to be the cleaner method of doing this. I wasn't aware that the .dot is so simple, and I will definitely use that way for similar problems.

Unfortunately I also have to analyse software components where the interface to other components are C functions - which are used through the extern keyword. They do not show up in the clang call graph because of an internal filter (includeInGraph (const Decl *D)) in clang::CallGraph.

So I had to copy clang::CallGraph, remove the limitation and use it in an clang::ASTConsumer like:

virtual void HandleTranslationUnit(clang::ASTContext &Context) {
    _visitor.TraverseDecl(Context.getTranslationUnitDecl());
    for (auto root : _visitor)
    {
        if (const clang::NamedDecl* namedDecl = llvm::dyn_cast_or_null<clang::NamedDecl>(root.first))
            if(namedDecl->getIdentifier() != nullptr && namedDecl->getIdentifier()->getName().startswith("Start"))
            {
                llvm::outs() << "StartFunc: " << namedDecl->getName() << "\n";
                printAFunctions(root.second);
            }
    }
}
void printAFunctions(const clang::CallGraphNode* node)
{
    if (node != nullptr)
    {
        if (const clang::NamedDecl* namedDecl = llvm::dyn_cast_or_null<clang::NamedDecl>(node->getDecl()))
        {
            if (namedDecl->getName().startswith("A_"))
            {
                llvm::outs() << "A_ call: " << namedDecl->getName() << "\n";
            }
        }
        for (auto subNode : *node)
        {
            printAFunctions(subNode);
        }
    }
}