Repository navigation
mem::swap doesn't work with Objects #6
Description
For example, the following code:
let mut a: Id<NSString> = INSString::from_str("a");
let mut b: Id<NSString> = INSString::from_str("b");
println!("{} {}", a, b);
mem::swap(a.deref_mut(), b.deref_mut());
println!("{} {}", a, b);Expected output:
a b
b a
Actual output:
a b
a b
We cannot have the expected output happen, because an NSObject's memory address cannot change after it has been constructed.
Activity
SSheldon commentedon Jan 17, 2015
The ideal fix for this would be to make NSObjects not
Sized; then the example code wouldn't even compile. Unfortunately, it doesn't seem that there's a way to make a struct notSizedwithout the struct using "fat" (two-word) references, which would be incorrect for an NSObject.SSheldon commentedon Jan 31, 2015
If rust-lang/rfcs#709 were accepted, this could be resolved by marking NSObjects as
NotSized.SSheldon commentedon Feb 11, 2015
The unsized types RFC was postponed as rust-lang/rfcs#813.
[-]mem::swap doesn't work with NSObjects[/-][+]mem::swap doesn't work with Objects[/+]SSheldon commentedon Apr 22, 2017
If rust-lang/rfcs#1861 is accepted, we could fix this by making Object an opaque extern type.
SSheldon commentedon Dec 6, 2017
The extern types RFC was accepted and implemented! Stabilization tracked in rust-lang/rust#43467.
nox commentedon Dec 11, 2017
Getting mutable references to void types is undefined behaviour to begin with, will file an issue.
Merge pull request SSheldon#6 from madsmtm/no-std-exception