CGO passing a function pointer to C

By default when passing a function as an argument, Cgo uses unsafe.Pointer. This will result in an IncompatibleAssign error.

In order to pass a function pointer as an argument to a C function, type conversion must be used. In the example below (*[0]byte) is used to convert C.print_hello to what C.invoke expects. (*[0]byte) is special, it means the same as void * in C.

package main

/*
#include <stdio.h>

static void invoke(void (*f)()) {
	f();
}

void print_hello() {
	printf("Hello, World!\n");
}
*/
import "C"

func main() {
	C.invoke((*[0]byte)(C.print_hello))
}