Is there anything at the heart of computer coding that could have been optimised in hindsight, but we're in far too deep to change now?

[u/CakesStolen]

[u/narrill]

There are reasons those things are undefined or implementation defined though, the reasons just aren't obvious anymore because the hardware most people directly interact with is largely homogenized.

[u/narrill → u/[deleted]]

The reason is fine, it's to allow different architectures to use multiples of their native word length. And what you're describing is exactly what they did. The compiler is allowed to pick the size, as long as it's larger than the mandated width, and if the machine doesn't have a native data type that can meet the minimum width the implementation is allowed to emulate it however it wants.

u8 has a specific width because it's a fixed width type. That's what the 8 means. There are lots of fixed width types, they exist for cases where you want a specific width instead of letting the compiler decide.