Bind function pointer to boost::function object

Question

How can I initialize a boost::function object with a raw function pointer?

Metacode

extern "C"
{
    class Library
    {
        ...
    };
    Library* createLibrary();
}

...

void* functionPtr = library.GetFunction("createLibrary");
boost::function<Library*()> functionObj(functionPtr);

Library* libInstance = functionObj();

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Answer 1

void* is not a function pointer, so you can't create a boost::function from it. You probably want to convert this to a proper function pointer first. How to do that is implementation dependent.

This is how this ugly conversion is recommended in POSIX (rationale):

void* ptr = /* get it from somewhere */;
Library* (*realFunctionPointer)(); // declare a function pointer variable
*(void **) (&realFunctionPointer) = ptr // hack a void* into that variable

Your platform may require different shenanigans.

Once you have such a pointer you can simply do:

boost::function<Library*()> functionObj(realFunctionPtr);

Library* libInstance = functionObj();