C++ : Extern C Functions inside a Namespace

Question

I have to link two libraries, say A and B. Some of the files are common in both libraries. So, I declare functions in library A inside a namespace, say abc. So, in A and B, a function func looks like below:

[ in A]

    namespace abc {
    extern "C" void func();
    }


[in B]

    extern "C" void func();

While building the project, compiler throws linking errors saying multiple definitions of function func. Isn't the function func in A inside the namespace or is there some problem with extern "C" functions. If there is, then how can I differentiate them both?

Answer 1

When you use Extern "C" you are turning off name mangling so you lose the namespace information as C has no such concept. This causes a duplicate definition.