CommandExt::before_exec: deprecate safety in edition 2024

[RalfJung]

Similar to set_var, we had to find out after 1.0 was released that before_exec should have been unsafe. We partially rectified this by deprecating that function a long time ago, but since #124636 we have the ability to also deprecate the safety of the old function and make it a hard error to call the old function outside unsafe in the next edition. So just in case anyone still uses the old function, let's ensure this can't be ignored when moving code to the new edition.

Cc @rust-lang/libs-api

Tracking:

• Tracking Issue for Rust 2024: Make std::env::{set_var, remove_var} unsafe #124866

[rustbot]

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[Amanieu]

The doc comment needs to be adjusted. It's confusing at the moment since before_exec now appears as an unsafe function in the docs.

[Noratrieb]

r? libs-api

[tbu-]

Needs a test. I'm not sure if this works since this isn't a free standing function.

[traviscross]

@rustbot labels +I-libs-api-nominated

Nominating for libs-api to decide whether to make calls to CommandExt::before_exec unsafe in the Rust 2024 edition, similar to what we're doing for std::env::{set_var, remove_var}.

If we decide to do this, we'll use that same tracking issue:

• Tracking Issue for Rust 2024: Make std::env::{set_var, remove_var} unsafe #124866

[RalfJung]

I extended the comment and added a test. It seems to be working fine.

[joshtriplett]

This function directly has a comment saying that it should be unsafe, and now we have a way to do that.

@rfcbot merge

[rfcbot]

Team member @joshtriplett has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

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[traviscross]

@rustbot labels -S-blocked +S-waiting-on-review

This had been blocked on #127857. That PR has now received an r+, so it's probably time to have another look at this.

Note that this is an edition item.

[RalfJung]

@m-ou-se I rebased, so this should be ready for review now. :)

[m-ou-se]

@bors r+

[bors]

📌 Commit 5ae0386 has been approved by m-ou-se

It is now in the queue for this repository.