4 ms·

thanks and is the padding for aligned access (wasted space) or just full byte (poor performance on non x86/64 like architecture)? because that's the interesting

by hawk_ 5y ago

thanks and is the padding for aligned access (wasted space) or just full byte (poor performance on non x86/64 like architecture)? because that's the interesting part as to what's the tradeoff chosen and whether a dev can choose a different one. Any doc references are appreciated.

Nullabillity 5y ago
They are padded for aligned access, so on amd64 Option<u64> will be 16 bytes.[0] However, the unused discriminant values are counted as niches for enums wrapping that, so Option<Option<u64>> is still 16 bytes (for example). [0]: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=ccfc6db189ae326a52d3d5187fce11fc https://play.rust-lang.org/?version=stable&mode=debug&editio...