3 ms·

I think the commenter made a guess that I was boxing an array, which is a good guess, it just happens to be wrong in this case. Maybe that will work in the fut

I think the commenter made a guess that I was boxing an array, which is a good guess, it just happens to be wrong in this case. Maybe that will work in the future—I don’t use nightly Rust, so for now, new_zeroed() won’t work. The basic problem is “I want to allocate something large on the heap” and it doesn’t seem like I should need to use nightly builds or unsafe{} to do it.

tialaramex 4y ago
> I don’t use nightly Rust, so for now, new_zeroed() won’t work That's a completely fair observation. The main thing I want stabilised is a single niche for custom types. I would take more if offered but experience says that every extra little thing doubles the discussion time, so, one niche is all I need, and Rust guarantees this exists in some form so even if a later mechanism does - say - fancy non-contiguous niches, I just want one value ASAP. https://github.com/rust-lang/rfcs/pull/3334 https://github.com/rust-lang/rfcs/pull/3334 > “I want to allocate something large on the heap” and it doesn’t seem like I should need to use nightly builds or unsafe{} to do it. The former makes sense to me, the latter (a requirement to use unsafe) I can see there can be cases where the compiler has to do a lot of contortions to safely but optimally mint the type in place in the heap and just writing the unsafe case is reasonable. I don't know anything about your type so I can't judge.
sli 4y ago
let heap_value = vec![the_struct]; Based on another comment addressing this, I don't think the original commentor was making assumptions about the shape of your data.
- klodolph 4y ago
  This doesn’t actually work, it will still overflow the stack. The vec! macro will just copy its arguments into the heap; the arguments are still on the stack to begin with.

3 ms·

I think the commenter made a guess that I was boxing an array, which is a good guess, it just happens to be wrong in this case. Maybe that will work in the fut

by klodolph 4y ago

tialaramex 4y ago
> I don’t use nightly Rust, so for now, new_zeroed() won’t work That's a completely fair observation. The main thing I want stabilised is a single niche for custom types. I would take more if offered but experience says that every extra little thing doubles the discussion time, so, one niche is all I need, and Rust guarantees this exists in some form so even if a later mechanism does - say - fancy non-contiguous niches, I just want one value ASAP. https://github.com/rust-lang/rfcs/pull/3334 https://github.com/rust-lang/rfcs/pull/3334 > “I want to allocate something large on the heap” and it doesn’t seem like I should need to use nightly builds or unsafe{} to do it. The former makes sense to me, the latter (a requirement to use unsafe) I can see there can be cases where the compiler has to do a lot of contortions to safely but optimally mint the type in place in the heap and just writing the unsafe case is reasonable. I don't know anything about your type so I can't judge.
sli 4y ago
let heap_value = vec![the_struct]; Based on another comment addressing this, I don't think the original commentor was making assumptions about the shape of your data.
- klodolph 4y ago
  This doesn’t actually work, it will still overflow the stack. The vec! macro will just copy its arguments into the heap; the arguments are still on the stack to begin with.