C++: cannot initialize a parameter of type 'void (*)()' with an rvalue of type 'void'

Question

I'm using GLUT with C++ and I'm calling a function called glutDisplayFunc with a single argument of the type void (*)(void). For some reason, when I use the following C++ method from one of my classes:

void EventHandler::Render(void) { ... }

It throws this error:

cannot initialize a parameter of type 'void (*)()' with an rvalue of type 'void'

Which seems to give me the thought that my C++ method isn't declared to properly comply with the argument type void (*)(void). What can I do to make my method work with this function parameter?

score 5 · Answer 1 · answered Sep 06 '13 at 20:53

5

A C++ method is not a normal function. It won't convert to a normal function pointer. You didn't show your actual code, but I'm assuming you did something like:

glutDisplayFunc(EventHandler::Render)

You need to make Render a static method if you want to use it this way. Otherwise declare a free function and use that.

answered Sep 06 '13 at 20:53

Carl Norum

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Then it's ok: http://stackoverflow.com/questions/5500057/how-to-define-a-function-pointer-pointing-to-a-static-member-function – Carl Norum Sep 06 '13 at 20:54
Declared as `static` and it works perfectly, thanks! – beakr Sep 06 '13 at 20:57
Unfortunately using static invkoes undefined, compiler dependent behavior. See my answer on the very same topic asked just yesterday: http://stackoverflow.com/a/18656082/524368 – datenwolf Sep 06 '13 at 22:35
I don't see anything about `static` in your answer. – Carl Norum Sep 06 '13 at 22:41
@CarlNorum: See my comment(s) to the other answer. – datenwolf Sep 07 '13 at 00:23

C++: cannot initialize a parameter of type 'void (*)()' with an rvalue of type 'void'

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