Proposal

Adds the -Z randomize-layout flag and infrastructure required for it. The randomize layout flag randomizes/shuffles/otherwise makes unpredictable the layout of repr(Rust) types, which do not have a specified layout. This is to aid in debugging programs, detecting undefined behavior and running crater experiments. This does not affect any types with specified layouts, such as #[repr(C)] or #[repr(transparent)] types. This is strictly an opt-in flag and will not affect current stable code unless the end user explicitly uses the -Z randomize-layout flag with a nightly compiler.

Mentors or Reviewers

@eddyb

Process

The main points of the Major Change Process are 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.