Fix buffer overrun in bootstrap and (test-only) symlink_junction

[thomcc]

I don't think these can be hit in practice, due to their inputs being valid paths. It's also not security-sensitive code, but just... bad vibes.

I think this is still not really the right way to do this (in terms of path correctness), but is no worse than it was.

r? @ChrisDenton

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[jyn514]

Can we switch to using docs.rs/junction instead? it makes me nervous to have all this unsafe code without tests ...

[thomcc]

Can we switch to using docs.rs/junction instead

For bootstrap that seems reasonable, done.

For std I'm less sure. Even if we can (not really sure -- for a dev-dep I think we don't need it to use special rustc-dep-of-std stuff? Although maybe it would need to be in integration tests to avoid that...), deps in std (even dev-deps) have a way of causing headaches -- I'll leave it up to the reviewer.

[albertlarsan68]

r=me on the bootstrap changes

[ChrisDenton]

I'll look at these changes in a bit but I'm definitely in favour of avoiding headaches 🙂. I think the ultimate solution is for me to finally write an ACP (which I'll do now before I forget), fix up the std function with tests and finally get it stabilized.

[ChrisDenton]

Ok this looks like an improvement, even if it's only avoiding an unlikely edge case. The new dependency looks fine for bootstrap though hopefully we can unify this code in a future libstd.

@bors r+

[bors]

📌 Commit 42e38e8 has been approved by ChrisDenton

It is now in the queue for this repository.