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Revision as of 18:49, 17 January 2023 by Bcotton (talk | contribs) (Change approved by FESCo)


GNU Toolchain Update (gcc 13.0, binutils 2.39, glibc 2.37, gdb 12.1)

Summary

Update the Fedora 38 GNU Toolchain to gcc 13.0, binutils 2.39, and glibc 2.37.

The existing gdb 12.1 will be used as-is.

The set of core GNU Toolchain packages for Fedora 38 are as follows:

  • GNU C Compiler 13.0
    • Associated runtimes for C++ (libstdc++), Go (gccgo), OpenMP (gomp), Fortran (gfortran), D (phobos), Objective C/C++.
  • GNU Binary Utilities 2.39
  • GNU C Library 2.37
  • GNU Debugger 12.1 (immediately available in Fedora 37)

The gcc 13.0 change will be tracked in this top-level GNU Toolchain system-wide update.

The binutils 2.39 change will be tracked in this top-level GNU Toolchain system-wide update.

The glibc 2.37 change will be tracked in this top-level GNU Toolchain system-wide update.

Owner

Current status

Detailed Description

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

The GNU Compiler Collection is expected to release version 13.0, after the Fedora 38 release. It will contain many new features, documented here: https://gcc.gnu.org/gcc-13/changes.html. The latest release candidate for gcc 13 will be included in Fedora 38 and will be updated when released.

The GNU Binutils version 2.39 was released before Fedora 38; and we have already been using this version of binutils in Fedora Rawhide successfully to build the distribution for the last 4 months. Given the present schedule for Fedora 38 we will continue to use Binutils 2.39.

The GNU C Library version 2.37 is expected to be release before Fedora 38; we have started closely tracking the glibc 2.37 development code in Fedora Rawhide and are addressing any issues as they arise. Given the present schedule Fedora 38 will branch after the release of glibc 2.37. However, the mass rebuild schedule means Fedora 38 will mass rebuild (if required) before the final release of glibc 2.37, but after the ABI is frozen.

The GNU Debugger version 12.1 was released before Fedora 38; and we plan to continue to use this version of the debugger.

Benefit to Fedora

Stays up to date with latest features, improvements, security and bug fixes from gcc, glibc, binutils, and gdb 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, ...) developers need to ensure that gcc, glibc, binutils, and gdb in rawhide are stable and ready for the Fedora 38 branch.
  • Other developers: 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: A mass rebuild is strongly encouraged; #XX
    • Filed after approval.
  • 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.

Some source changes may be required for the gcc 13 update. Please refer to the latest changes here: https://gcc.gnu.org/gcc-13/changes.html

Any source level changes required for glibc 2.37 will be noted here: https://sourceware.org/glibc/wiki/Release/2.37#Packaging_Changes

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 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 we may also run the microbenchmark to look for performance regressions.

The GNU Binutils has its own testsuite which is run during the package build and examined by binutils developers before being uploaded. The regression testsuite is run to verify the correct operation of the static linker and attendant utilities.

The GNU Debugger has its own testsuite which is run during the package build and examined by gdb developers before being uploaded. The regression testsuite is run to verify the correct operation of the debugger.

User Experience

Fedora developers as well as developers using the distribution will be able to use and develop using the new features offered by the updated components. Developers will need to enable specific compiler features as required e.g. '-mcpu=neoverse-v2'.

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 38 cycle. The mass rebuild would ensure all packages can be built with the newer compiler and core runtime.

Contingency Plan

  • Contingency mechanism glibc: If glibc 2.37 proves too disruptive to compiling the distribution we could revert to 2.36, but given that Rawhide has started tracking glibc 2.37, no show-stopper problems are expected. At this point we can still revert to upstream version 2.36 if insurmountable problems appear, but to do so may require a mass rebuild to remove new symbols from the ABI/API.
  • Contingency mechanism binutils: If binutils 2.39 proves too distruptive to assembling and linking the distribution we could revert to 2.38, but given that Rawhide is using 2.39, no show-stopper problems are expected. At this point we can still revert if insurmountable problems appear, but to do so may require a mass rebuild if the defects involve generated binaries.
  • Contingency mechanism for gcc: If gcc 13 proves too disruptive to compiling the distribution we could revert to gcc 12.
  • Contingency mechanism for gdb: The gdb 12.1 release is already in all the Fedora releases and it would not be reverted. If any gcc, glibc or binutils changes cause gdb to fail then that would need to be reviewed on a case-by-case basis.
  • Contingency deadline: Fedora mass rebuild on 2023-01-18.
  • Blocks release?
    • Yes, upgrading to gcc 13.0 does block the release.
    • Yes, upgrading to binutils 2.39 does block the release.
    • Yes, upgrading to glibc 2.37 does block the release.
    • No, upgrading to gdb 12.1 does block the release (already released).


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

See https://gcc.gnu.org/gcc-13/changes.html for the GNU Compiler Collection version 13 release notes.

The GNU C Library version 2.37 will be released at the beginning of February 2023. 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

The GNU Binary Utilities version 2.39 was released August 2022. The current release notes will be sent to the developer mailing list: https://sourceware.org/pipermail/binutils/2022-August/122246.html.

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