A few suggestions regarding unsafe code

[joshlf]

While reviewing a commit to vendor new versions of various rand crates into Fuchsia's source tree, a reviewer came across a few issues. I'm not sure that they all deserve to be acted on, so I figured I'd just bring them to the authors' attention here and let y'all decide if they're worth opening issues for.

Visit https://fxrev.dev/569847 and click on the "Comments" tab. There are three unresolved comments, each of which contains suggestions about how to improve or remove unsafe code.

cc @Ralith

[josephlr]

@joshlf it seems like all the comments are now resolved. Other than #1169, which specific comments contain issues that we should fix here.

Also, thank you for looking into this.

[joshlf]

Ah, I'm sorry, it looks like a different reviewer marked those as resolved after I posted this issue. Here's the list I was referring to:

• https://fuchsia-review.googlesource.com/c/fuchsia/+/569847/3/third_party/rust_crates/vendor/rand_chacha/src/chacha.rs#93
• https://fuchsia-review.googlesource.com/c/fuchsia/+/569847/3/third_party/rust_crates/vendor/rand_core/src/impls.rs#79
• https://fuchsia-review.googlesource.com/c/fuchsia/+/569847/3/third_party/rust_crates/vendor/rand_core/src/impls.rs#69

[vks]

I think all issues mentioned here are fixed now, except that we still use copy_nonoverlapping for performance reasons (see here).

[dhardy]

Yes, but I just noticed a perf regression in #1181 so it may need revisiting.

I also created #1182.

[sneurlax]

Are all of these issues resolved?

[dhardy]

All code mentioned has been re-written in master so we might as well close this.

Not all of these changes have made it into releases yet, but I'm not aware of any pressing concerns here.