Changes/GNUToolchainF36

GNU Toolchain Update (gcc 12, glibc 2.35, binutils 2.38, gdb 11.1)

Summary

Switch the Fedora 36 GNU Toolchain to gcc 12, binutils 2.38, glibc 2.35, and gdb 11.1.

The gcc 12 is currently under development and will be included in Fedora 36 upon release. The glibc 2.35 change will be tracked in this top-level GNU Toolchain system-wide update. Likewise the binutils 2.38 release will be tracked in this top-level GNU Toolchain system-wide update. The gdb 11.1 is already in Fedora 36 but will be updated to the latest point release.

Owner

• Name: Arjun Shankar
• Email: arjun@redhat.com

Current status

• Targeted release: Fedora Linux 36
• Last updated: 2022-01-04
• FESCo issue: <will be assigned by the Wrangler>
• Tracker bug: <will be assigned by the Wrangler>
• Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

The GNU Compiler Collection, GNU C Library, GNU Debugger, and GNU Binary Utilities make up the core part of the GNU Toolchain and it is useful to transition these components as a complete implementation when making a new release of Fedora.

The GNU Compiler Collection is expected to release version 12 containing many new features documented here: https://gcc.gnu.org/gcc-12/changes.html. The latest point release for gcc 12 will be included in Fedora 36, this will most probably be 12.1.

The GNU C Library version 2.35 is expected to be released in the beginning of February 2022; we have started closely tracking the glibc 2.35 development code in Fedora Rawhide and are addressing any issues as they arise. Given the present schedule Fedora 36 will branch after the release of glibc 2.35. However, the mass rebuild schedule means Fedora 36 will mass rebuild (if required).

The GNU Binutils version 2.38 will be released near the end of January 2022.

The GNU Debugger verion 11.1 is already released.

Benefit to Fedora

Stays up to date with latest features, improvements security and bug fixes from gcc, binutils, gdb and glibc upstream.

The goal is to track and transition to the latest components of the GNU Toolchain.

Scope

• Proposal owners: Fedora Toolchain Team (gcc, glibc, binutils, gdb, ...)

• Other developers: Developers need to ensure that gcc, binutils, gdb, and glibc in rawhide are stable and ready for the Fedora 36 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. An update to GCC 12.1 would be mean a new major release and could have broad scope for change. The binutils 2.38 update also has the broad scope for change and generated object files should be reviewed and failures to build analyzed.

• Release engineering: #Releng issue number

A mass rebuild is strongly encouraged.

• Policies and guidelines: N/A (not needed for this Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Objectives: N/A

Upgrade/compatibility impact

The compiler, the static linker and the the library are backwards compatible with the previous version of Fedora.

The upgrade to glibc-2.35 coincides with the removal of nscd.

Some source changes may be required for gcc 12 rebase: https://gcc.gnu.org/gcc-12/changes.html

There should be no need for any changes to accommodate the new GNU Binutils release.

We fully expect to fix all packaging changes in Fedora Rawhide without impact to the release.

How To Test

The GNU Compiler Collection has its own testsuite which is run during the package build and examined by the gcc developers before being uploaded.

The GNU Binary Utilities has its own testsuite which is run during the package build and examined by the binutils developers before being uploaded.

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.

The GNU Debugger has its own testsuite which is run during the package build and examined by the gdb developers before being uploaded.

User Experience

Users will see improved performance, many bugfixes and improvements to POSIX compliance, Unicode 14 support, C.UTF-8 locale support, etc.

Dependencies

All packages do not need to be rebuilt due to backwards compatibility. However, it is advantageous if a mass rebuild is performed during the Fedora 36 cycle.

Contingency Plan

• Contingency mechanism: If glibc 2.35 provides too disruptive to compiling the distribution we could revert to 2.34, but given that Rawhide has started tracking glibc 2.35, no show-stopper problems are expected. At this point, we can still revert to upstream version 2.34 if insurmountable problems appear, but to do so may require a mass rebuild to remove new symbols from the ABI/API.
• Contingency deadline: Upstream glibc ABI freeze deadline of 2021-01-01.
• Blocks release? Yes, upgrading to the gcc 12 release blocks the release. Yes, upgrading to binutils 2.38 blocks the release. Yes, upgrading glibc does block the release.

Documentation

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

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

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

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

Release Notes

The GNU Compiler Collection version 12 is soon to be released. See https://gcc.gnu.org/gcc-12/changes.html.

The GNU Binutils version 2.38 will be released in January 2022 and release notes will be updated at that point.

The GNU Debugger version 11.1 release notes are available here: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob_plain;f=gdb/NEWS;hb=gdb-11.1-release

The GNU C Library version 2.35 will be released at the beginning of August 2021. 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