Class Pointer Size in C++

Hi. What is the size in bytes that a class pointer in c++ has?.

For example:

Having a class named KuRiClass in a Dll.

KuRiClass *instance1;

Can i store the pointer in a blitz3d variable (return instance1) then later pass it to a function in the Dll.

The only problem i see here is that the pointer could be destroyed after the function if it is not a global variable?

Thanks.