fix(vm): Don't let rustc think the Array type can't exist #398
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THe use of `Void` in the `Array` type was meant to absolutely prevent the `Array` type from existing except behind a pointer which is invalid (except the empty array I guess) as the elements are stored inline behind the length field. Unfortunately rust-lang/rust#45225 made rustc think that fields of the `Array` type could not exist at all and placed fields of `Array` at the start of any struct containing them, causing any write to the `Array` to overwrite other fields.
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Since having a valid value of type |
brendanzab
reviewed
Nov 25, 2017
vm/src/array.rs
Outdated
| /// Abstract array type which have their length store inline with the elements. | ||
| /// Fills the same role as Box<[T]> but takes only 8 bytes on the stack instead of 16 | ||
| #[repr(C)] | ||
| pub struct Array<T: Copy> { | ||
| len: usize, | ||
| array_start: [T; 0], | ||
| _marker: self::internal::CantConstruct, |
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I thought just having private fields meant that folks couldn't construct it 🤔
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I think the intention is that it shouldn't be constructed even accidentally from this module.
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The use of
Voidin theArraytype was meant to absolutely prevent theArraytype from existing except behind a pointer which is invalid (except the empty array I guess) as the elements are stored inline behind the length field.Unfortunately rust-lang/rust#45225 made rustc think that fields of the
Arraytype could not exist at all and placed fields ofArrayat the start of any struct containing them, causing any write to theArrayto overwrite other fields.Fixes #396