__typeof_ is a compile-time feature. It's like C++'s decltype. (You can make C++'s auto out of it too.) There's is a potential for code size increases with this approach, that's true. But the potential also exists with inlinable vector methods.

Yes, but for the vector methods, you leave that decision up to the compiler which should be able to take the best route.

True. However, I think in the case of the dynamic array, this effect is minor. The macros are small, and most of the time, they end up wrapped in a function anyway. But, admittedly,it doesn't scale well to very big generics, which should be always wrapped in a function. (Eventually I plan to shove a simple transpiler in front of all my C code and do this, along with namespacing, how I think it should be done.)