`#[deny(unsafe_op_in_unsafe_fn)]` in liballoc

[LeSeulArtichaut]

Proposal

Deny the newly-added unsafe_op_in_unsafe_fn lint in liballoc, which means that unsafe operations inside unsafe functions require an explicit unsafe block.

Motivation

This is an opportunity for the language team to see the impact of the lint and decide of its future. It is also useful in the context of liballoc, where there are a lot of unsafe functions containing both safe and unsafe operations.

Drawbacks

If the lint is removed, these additional unsafe blocks should be removed. However, this can probably be done automatically using e.g. cargo fix.

Links

• Tracking Issue for "unsafe blocks in unsafe fn": Tracking Issue for "unsafe blocks in unsafe fn" (RFC #2585) rust#71668
• Proposed "implementation" PR: #[deny(unsafe_op_in_unsafe_fn)] in liballoc rust#72709

Mentors or Reviewers

@Mark-Simulacrum is willing to second this. @RalfJung may also review as well?

Process

The main points of the Major Change Process is as follows:

• File an issue describing the proposal.
• A compiler team member or contributor who is knowledgeable in the area can second by writing @rustbot second.
  • Finding a "second" suffices for internal changes. If however you are proposing a new public-facing feature, such as a -C flag, then full team check-off is required.
  • Compiler team members can initiate a check-off via @rfcbot fcp merge on either the MCP or the PR.
• Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

Comments

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

[nikomatsakis]

@bors second

I'd like us to see more this feature "weathers" in libstd, and the downsides of this seem quite minimal.

[nikomatsakis]

@rustbot second

ETOOMANYBOTS