0.15

CHANGES:

New features:

• eio_posix: use directory FDs instead of realpath (@talex5 #694 #696, reviewed by @SGrondin).
  Using realpath was an old hack from the libuv days and subject to races. It was also slow.

• Keep pool of systhreads for blocking operations (@SGrondin @talex5 #681).
  This is much faster than creating a new thread for each operation.
  It mainly benefits the eio_posix backend, as that uses lots of systhreads.

• Make Switch.on_release thread-safe (@talex5 #684, requested by @art-w and @clecat).
  This allows resource pools to be shared between domains easily.

• Add Eio.Path.read_link (@talex5 #686).

• Add Eio_unix.Fd.is_open (@talex5 #690).

• Include backtrace in systhread errors (@talex5 #688, reviewed by @SGrondin).
  Also, add Eio.Exn.empty_backtrace as a convenience.

• eio.mock: add tracing support to mock backend (@talex5 #687).

• Improve tracing (@talex5 #675 #683 #676, reviewed by @SGrondin).
  Update tracing section of README and trace more things
  (run_in_systhread, close, submit, traceln, cancellation and domain spawning).

Documentation:

• Link to verification work in docs (@talex5 #682).

• Add more trace diagrams to README (@talex5 #698).

• Adjust COC contacts (@polytypic #685, reviewed by @Sudha247).

Bug fixes:

• eio_linux: retry openat2 on EAGAIN (@talex5 #693, reviewed by @SGrondin).

• eio_posix and eio_windows: check for IO periodically (@talex5 #674).

• Handle EPERM when trying to initialise uring (@talex5 #691).
  This can happen when using a Docker container.

Build and tests:

• Benchmark Eio_unix.run_in_systhread (@talex5 #678, reviewed by @SGrondin).

• Enable lintcstubs for Eio_unix.Private too (@talex5 #689).

• Stat benchmark: report cleanup time and optimise (@talex5 #692).

• Make benchmarks start faster (@talex5 #673).

• Update build for new eio-trace CLI (@talex5 #699).

• Expect opam-repo-ci tests to fail on macos (@talex5 #672).