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The GNU C Library version 2.31

Summary

Switch glibc in Fedora 32 to glibc version 2.31.

Owner

Current status

Detailed Description

The GNU C Library version 2.31 will be released at the beginning of February 2020; we have started closely tracking the glibc 2.31 development code in Fedora Rawhide and are addressing any issues as they arise. Given the present schedule Fedora 32 will branch after the GLIBC 2.31 upstream release. However, the mass rebuild schedule means Fedora 32 will mass rebuild (if required) after GLIBC 2.31 upstream freezes ABI for release, but before the actual release, so careful attention must be paid to any last minute ABI changes.

Benefit to Fedora

Stays up to date with latest security and bug fixes from glibc upstream.

Scope

  • Proposal owners: Update glibc to 2.31.
  • Other developers: Developers need to ensure that rawhide is stable and ready for the Fedora 32 branch. Given that glibc is backwards compatible and we have been testing the new glibc in rawhide it should make very little impact when updated, except for the occasional deprecation warnings and removal of legacy interfaces from public header files.
  • Release engineering: #9040
  • Policies and guidelines: The policies and guidelines do not need to be updated.
  • Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

The library is backwards compatible with the version of glibc that was shipped in Fedora 31.

Some packaging changes required, see: https://sourceware.org/glibc/wiki/Release/2.31#Packaging_Changes

We fully expect to fix all packaging changes in Fedora Rawhide given that glibc in Rawhide is tracking what will become glibc 2.31.

How To Test

The GNU C Library has its own testsuite, which is run during the package build and examined by the glibc developers before being uploaded. This test suite has over 6200 tests that run to verify the correct operation of the library. In the future may also run the microbenchmark to look for performance regressions.

User Experience

Users will see improved performance, many bugfixes and improvements to POSIX compliance, additional locales, etc. The glibc 2.31 NEWS update will include more details.

Dependencies

All packages do not need to be rebuilt.

Contingency Plan

  • Contingency mechanism: Given that Rawhide has started tracking glibc 2.31, no show-stopper problems are expected. At this point, we can still revert to upstream version 2.30 if insurmountable problems appear, but to do so may require a mass rebuild to remove new symbols from the ABI/API.
  • Contingency deadline: Upstream ABI freeze deadline of 2020-01-01.
  • Blocks release? Yes, upgrading glibc does block the release. We should not ship without a newer glibc, there will be gcc and language features that depend on glibc being upgraded. Thus without the upgrade some features will be disabled or fall back to less optimal implementations.

Documentation

The glibc manual contains the documentation for the release and doesn't need any more additional work.

Release Notes

The GNU C Library version 2.31 will be released at the beginning of February 2020. The current NEWS notes can be seen here as they are added: https://sourceware.org/git/?p=glibc.git;a=blob;f=NEWS;hb=HEAD

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