Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

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Why would this be a "breakage candidate"? Because it changes ELAST? ELAST on OS that use this convention is defined as being the largest errno. It's only intended to be used to allow checks to see if an error is within the known values for errno, and things of that nature, it's not really directly used by any API. It is "versioning in userspace", as it were.

Why would this be a "breakage candidate"? Because it changes ELAST? ELAST on OS that use this convention is defined as being the largest errno. It's only intended to be used to allow checks to see if an error is within the known values for errno, and things of that nature, it's not really directly used by any API. It is "versioning in userspace", as it were.

Yes, and I think it could cause a bug (or any weird behavior due to lack of errno) if the last value points to a newer number while the user env is older.
As you mentioned on #3131, we just should not provide such a const, I think.

Hmm. I think that would be due to invalid reasoning on the part of the programmer, which we can't completely protect people from, but I agree that it's in any case quite silly from the Rust PoV.

One option:

• Merge this change with the updated ELAST value, but also with a deprecation notice. People who are using ELAST "correctly" don't have to change anything immediately, so it doesn't introduce bugs in code that was written to be future-proof, but they can use the deprecation notice to prepare. People who were using it incorrectly have a heads up.

I think in this case having an errno with a larger value than ELAST is equally likely to introduce bugs, unfortunately.

Noting that #1902 was handled by leaving the value in place and deprecating it, though that time we said we'd change it.

@0-wiz-0 Could you apply this?

• Merge this change with the updated ELAST value, but also with a deprecation notice. People who are using ELAST "correctly" don't have to change anything immediately, so it doesn't introduce bugs in code that was written to be future-proof, but they can use the deprecation notice to prepare. People who were using it incorrectly have a heads up.

@rustbot author

@JohnTitor I've added a deprecation warning as requested. Did I do it correctly?

Yeah, thanks!
@bors r+

📌 Commit 06fdfac has been approved by JohnTitor

It is now in the queue for this repository.

⌛ Testing commit 06fdfac with merge 9e90211...

☀️ Test successful - checks-actions, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing 9e90211 to master...