1413639 - u2f-hid-rs: variable does not need to be mutable warning on windows

Status: RESOLVED DUPLICATE of bug 1413598

(Core :: DOM: Device Interfaces, defect)

Description

[Ralph Giles (:rillian)]

u2fhid warns on windows targets:

warning: variable does not need to be mutable
   --> src/windows/winapi.rs:198:13
    |
198 |         let mut data = unsafe { libc::malloc(size) as PSP_DEVICE_INTERFACE_DETAIL_DATA_W };
    |             ^^^^^^^^
    |
    = note: #[warn(unused_mut)] on by default

    Finished dev [unoptimized + debuginfo] target(s) in 24.66 secs

Comment 1

[Ralph Giles (:rillian)]

Attachment: Bug 1413639: u2f-hid-rs: Remove unnecessary mut annotation.

Fix a warning when building for windows targets.

Data here doesn't need to be mutable. The contents of the struct
are modified inside the unsafe block, and that's allowed because
libc::malloc() returns a *mut. But the value of the binding itself,
that is, the location in memory that data references, never changes.

Review commit: https://reviewboard.mozilla.org/r/195464/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/195464/

Comment 2

[J.C. Jones [:jcj] (he/him)]

Comment on attachment 8924253 [details]
Bug 1413639: u2f-hid-rs: Remove unnecessary mut annotation.

Moving this to Tim, who is closer to this code

Comment 3

[Tim Taubert [:ttaubert] (inactive)]

Comment on attachment 8924253 [details]
Bug 1413639: u2f-hid-rs: Remove unnecessary mut annotation.

https://reviewboard.mozilla.org/r/195464/#review200924

Thanks for the patch, Ralph! I'm about to land https://phabricator.services.mozilla.com/D181 which already contains a fix for this warning. Let's dupe this.