Fabian Schmalzried (Jan 15 2023 at 22:14): Fabian Schmalzried (Jan 15 2023 at 22:14):Hi everyone, there is a question that popped into my head recently. I'm not sure if the question makes sense, and to what extent it makes any difference at all. I don't know much about low-level stuff so far.
So here's how I understand it: if I have a [Small U8, Large U64], the maximum necessary memory on the stack is allocated for it (because we need to know the size at compile time).
But how does it look when I move it to the heap (Box [Small U8, Large U64]). If there is actually a Small U8 in the box, will there still be room for a U64 on the heap, or actually only for the U8? Or is that even something that the platform can decide?
Ayaz Hafiz (Jan 15 2023 at 23:08):A box allocates on the heap what would otherwise be allocated on the stack - so in this case the memory needed to store a “Large U64” would be allocated on the heap (via roc_alloc) even if you are boxing a “Small U8” variant of the tag
Ayaz Hafiz (Jan 15 2023 at 23:10):One wrinkle here is that boxing calls “roc_alloc”, which a platform can implement as it likes - so you could implement that as malloc, or something generally more efficient like for example an arena allocator. So while a platform can’t control the memory layout of a Boxed value, it can control where in memory it will ultimately end up
Last updated: Jul 26 2025 at 12:14 UTC