Odin ends up pointlessly carrying around Allocator structures for each such container, each of which is two words (so e.g. 16 bytes on a modern system) because of how Odin works.
So e.g. that growable array of i64 you've asked for - just the data structure itself, not the array which was the whole point - needs 40 bytes on a modern machine because it has 8 bytes for a pointer to the array, 8 bytes for the size of that array, 8 bytes for how much was used, 8 bytes for a pointer to the allocator procedures and 8 bytes for a (sometimes unused) metadata structure for that allocator.
It's not a huge amount of waste, but what you get for it isn't worth it.
In Zig they're at least not paying for this with runtime space, they're paying for it with the programmer's need to make sure they talk about the same allocator everywhere.
So e.g. that growable array of i64 you've asked for - just the data structure itself, not the array which was the whole point - needs 40 bytes on a modern machine because it has 8 bytes for a pointer to the array, 8 bytes for the size of that array, 8 bytes for how much was used, 8 bytes for a pointer to the allocator procedures and 8 bytes for a (sometimes unused) metadata structure for that allocator.
It's not a huge amount of waste, but what you get for it isn't worth it.
In Zig they're at least not paying for this with runtime space, they're paying for it with the programmer's need to make sure they talk about the same allocator everywhere.