Thread: macros: can i test if a function was defined?

No, you can't do this with macros, because macros are evaluated before function definitions are evaluated.

There are several facilities in c++ that allow choosing between a specialized behavior, and a general purpose behavior if the specialization does not exist. These work such that at the call site calls the most general function, but a specialized implementation is invoked based on the type of th object calling it.

For example

Code:

class DefaultContext {};
struct ClsContext { //I'm only using a struct here to keep the example short. 
    Cls * clsPtr;
};

void mouseClick(DefaultContext)
{
   mouseClick();
}

void mouseClick(ClsContext context)
{
   context.clsPrt->mouseClick();
}

int main()
{
  auto context = someFactoryToGetContext();
  mouseClick(context); // calls the correct function depending on the context type.
}