I agree with what you say about ECS and the memory hierarchy. But not much else.
> inheritance almost always means virtual functions
Inheritance and "virtual functions" (dynamic method dispatch) are almost, but not completely, unrelated. You can easily have either one without the other. Golang and Lua have dynamic method dispatch without inheritance; C++ bends over backwards so that you can use all the inheritance you want without incurring any of the costs of dynamic method dispatch, as long as you don't declare anything virtual. This is actually a practical thing to do with modern C++ with templates and type inference.
> No - if you put A and B in separate allocations, you get worse performance
Yes, that's what I was saying.
> you're putting more pressure on the allocator / garbage collector
Yes, I explained how that happens in greater detail in the comment you were replying to.
With your struct C, it's somewhat difficult to solve the problem catern was saying Simula invented inheritance to solve; if A is "list node" and B is "truck", when you navigate to a list node p of type A*, to get the truck, you have to do something like &((struct C *)p)->b, relying on the fact that the struct's first field address is the same as the struct's address and on the fact that the A is the first field. While this is certainly a workable thing to do, I don't think we can recommend it without reservation on the basis that "you don't get any class entanglement, or any of the bugs"! It's very error-prone.
> Games are moving away from OO because C++ style OO
There are a lot of things to criticize about C++, but I think one of its worst effects is that it has tricked people into thinking that C++ is OO. "C++ style OO" is a contradiction in terms. I mean, it's possible to do OO in C++, but the language fights you viciously every step of the way; the moment you make a concession to C++ style, OO collapses.
> inheritance almost always means virtual functions
Inheritance and "virtual functions" (dynamic method dispatch) are almost, but not completely, unrelated. You can easily have either one without the other. Golang and Lua have dynamic method dispatch without inheritance; C++ bends over backwards so that you can use all the inheritance you want without incurring any of the costs of dynamic method dispatch, as long as you don't declare anything virtual. This is actually a practical thing to do with modern C++ with templates and type inference.
> No - if you put A and B in separate allocations, you get worse performance
Yes, that's what I was saying.
> you're putting more pressure on the allocator / garbage collector
Yes, I explained how that happens in greater detail in the comment you were replying to.
With your struct C, it's somewhat difficult to solve the problem catern was saying Simula invented inheritance to solve; if A is "list node" and B is "truck", when you navigate to a list node p of type A*, to get the truck, you have to do something like &((struct C *)p)->b, relying on the fact that the struct's first field address is the same as the struct's address and on the fact that the A is the first field. While this is certainly a workable thing to do, I don't think we can recommend it without reservation on the basis that "you don't get any class entanglement, or any of the bugs"! It's very error-prone.
> Games are moving away from OO because C++ style OO
There are a lot of things to criticize about C++, but I think one of its worst effects is that it has tricked people into thinking that C++ is OO. "C++ style OO" is a contradiction in terms. I mean, it's possible to do OO in C++, but the language fights you viciously every step of the way; the moment you make a concession to C++ style, OO collapses.