C++ Using Class Method as a Function Pointer Type

Question

In a C lib, there is a function waiting a function pointer such that:

lasvm_kcache_t* lasvm_kcache_create(lasvm_kernel_t kernelfunc, void *closure)
         


        

Answer 1

Every C++ member function has an implicit, hidden, first parameter, this.

So the method double cls_lasvm::kernel(int i, int j, void* kparam) is really: double cls_lasvm::kernel(cls_lasvm* this, int i, int j, void* kparam), and it is inappropriate/impossible to use it as a function-pointer parameter.

To make progress, convert your method to be a static-member-method. That will remove the this pointer. You may still have other issues to overcome, but that is a good start.