[vignesh-chaturvedi]

This PR stops declaring flock for target_os = "espidf".

Both newlib and picolibc declare flock in sys/_default_fcntl.h, but I couldn't find an implementation in either library or ESP-IDF. Using flock on this target would therefore result in a linker error. ivmarkov also confirmed that ESP-IDF does not support it and suggested excluding it for this target (discussion).

Fixes rust-lang/libc#4723. Emscripten and Redox will keep flock in libc, as Ralf suggested that the symbols should remain available even though their implementations are incorrect.

I've kept flock in libc-test/semver/unix.txt. ESP-IDF isn't built in CI, so the API list isn't checked against that target. Solaris only passes that check because it has a struct flock.

Testing

Ran:

RUSTFLAGS=-Dwarnings cargo +nightly check -Zbuild-std=core --target riscv32imc-esp-espidf

libc::flock no longer resolves on ESP-IDF.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[tgross35]

Cc @ivmarkov, this is what you suggested in #4723 (comment)

[tgross35]

I think this is fine, thank you!

View changes since this review

[ivmarkov]

@tgross35 Thank you for your fast reaction!

Unfortunately, the fix needs to reach Rust STD as well, or in other words, we need a libc 0.2 release (and then I can PR a libc version bump to the Cargo.toml of STD).

Is there anything I can help with to expedite this?

[tgross35]

I added the nominated label (for future reference can be added via rustbot) but what needs to be updated in std? It can't be using flock on espidf today, otherwise that would be a linker failure IIUC.

[ivmarkov]

I added the nominated label (for future reference can be added via rustbot) but what needs to be updated in std? It can't be using flock on espidf today, otherwise that would be a linker failure IIUC.

@tgross35
Ahhh.... sorry - I confused this issue with #5662. When (or if) #5662 is merged, then we would need a new libc 0.2 release.