C++ void pointer parameter

The function makes an assumption about what the actual type is, makes an (in)appropriate cast and operates on cast type.

Most userdata parameters are eventually passed back into your code at some time using a callback, or stored in a data structure that you can query later. Generally speaking, API's using void pointer userdata do not touch the value at all.

It casts it back to something non-void - ideally a bool* in this case. Hopefully something no bigger than a bool, or it will trash memory. The function could look something like:

function1(int param1, int param2, int param3, void *userData)
{
*((bool*)userData) = false;
}

Of course normally you'd declare the function parameter type as bool* as it's less error prone. void* is usually only used when either the function wants to take a buffer holding any type (e.g. memcpy() takes void* parameters) or when the function is a callback and you don't know what type of parameter the user will want (e.g. CreateThread() takes a pointer to a function with a void* argument as well as a void* value to call that function with).

Edit: I type too slow

okay. cheers.