1339218 - Re-introduce ns{Fixed,}{C,}StringRepr

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Nika Layzell [:nika] (ni? for response)]

Unfortunately, we still need to have a representation of ns{Fixed,}{C,}StringRepr in tree, as some FFI structs need to control and run their destructors independently. Not providing a drop-implementation-free version of these types means that they are unusable in those situations, such as in the style bindings.

This may be avoidable when `union` is stabilized in rust, as that will allow for structs which contain a value of a type to control whether or not that type's destructor gets run. (https://github.com/rust-lang/rust/issues/32836)

This patch will pretty-much be a backout of bug 1316696.

Comment 1

[Nika Layzell [:nika] (ni? for response)]

Attachment: Re-introduce the ns[C]StringRepr type for use in bindings with custom destructor logic

MozReview-Commit-ID: 3VUWFA5tX1L

Comment 2

[Nathan Froyd [:froydnj]]

Comment on attachment 8836901 [details] [diff] [review]
Re-introduce the ns[C]StringRepr type for use in bindings with custom destructor logic

Review of attachment 8836901 [details] [diff] [review]:
-----------------------------------------------------------------

rs=me on the presumption that this is a revert of the backout.

Comment 3

[Nika Layzell [:nika] (ni? for response)]

Comment on attachment 8836901 [details] [diff] [review]
Re-introduce the ns[C]StringRepr type for use in bindings with custom destructor logic

This isn't exactly just a backout, as I still wanted ns[C]String to be `#[repr(C)]` which was also added in that patch, and I wanted to verify that both the ns[C]StringRepr and ns[C]String had the correct layout. 

I'd appreciate it if you could look over the changes a bit more closely :).

Comment 4

[Nathan Froyd [:froydnj]]

Comment on attachment 8836901 [details] [diff] [review]
Re-introduce the ns[C]StringRepr type for use in bindings with custom destructor logic

Review of attachment 8836901 [details] [diff] [review]:
-----------------------------------------------------------------

::: xpcom/rust/nsstring/src/lib.rs
@@ +843,5 @@
> +                                  align: *mut usize,
> +                                  offset: *mut usize) {
> +                unsafe {
> +                    // Create a temporary value of type T to get offsets, sizes
> +                    // and aligns off of

I think "...and alignments from" reads better, WDYT?

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/7ecbacf4e84c
Re-introduce the ns[C]StringRepr type for use in bindings with custom destructor logic, r=froydnj

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/7045bd028af0
Comment wording fixup, r=me

Comment 7

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/7ecbacf4e84c
https://hg.mozilla.org/mozilla-central/rev/7045bd028af0