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memcpy is declared like
void* memcpy(void* dst, void* src, size_t size); which is to say it accepts any pointer for the params so why should it be any problem to use a pointer to the correct type?...

Casts are pure evil when used (without a deep understanding) just to solve a compiler error and I think this shows that you are in deep water at the moment
I would advise you to get rid of all casts...