Changes/GNUToolchainF39

GNU Toolchain Update (gcc 13.2, binutils 2.40, glibc 2.38, gdb 13.2)

Summary

Update core components

Update the Fedora 39 GNU Toolchain to gcc 13.2, binutils 2.40, glibc 2.38 and gdb 13.2.

The set of core GNU Toolchain packages for Fedora 39 are as follows:

• GNU C Compiler 13.2 (Expected in August 2023)
  • Associated runtimes for C++ (libstdc++), Go (gccgo), OpenMP (gomp), Fortran (gfortran), D (phobos), Objective C/C++.
• GNU Binary Utilities 2.40 (Released February 2023)
• GNU C Library 2.38 (Expected August 2023)
• GNU Debugger 13.2 (Released May 2023)
  • Note: Already available in Fedora 38.

The gcc 13.2 change will be tracked in this top-level GNU Toolchain system-wide update. Currently Fedora Rawhide and 38 are already using gcc 13.1, and 13.2 is expected to release in August 2023 with additional fixes.

The binutils 2.40 change will be tracked in this top-level GNU Toolchain system-wide update. Currently Fedora Rawhide has been testing binutils 2.40 since Feburary 13th, 2023.

The glibc 2.38 change will be tracked in this top-level GNU Toolchain system-wide update. Currently Fedora Rawhide has been testing glibc 2.38 since Feburary 20th 2023.

The gdb 13.2 update was rolled out across all Fedora releases and the move to 13+ will be handled in the same fashion. The debugger is capable of debugging the binary artifacts produced by the rest of the system toolchain.

Enable DT_RELR

Enable DT_RELR (all architectures) to allow packing of relative relocations in a binary. The current glibc binary rpms are already built this way e.g. GLIBC_ABI_DT_RELR, and tooling must support it already. Some bootloaders etc. may need adjustment due to missing DT_RELR support in self-relocation.

In general the benefit to Fedora is faster startup times for applications.

This work adds code in redhat-rpm-config and documentation in buildflags.md.

Enable warnings

Early work for Fedora 40's Port to Modern C is complete ahead of schedule, and it would be good to avoid regressing the progress that has been made by a limited enabling of -Werror=implicit-function-declaration and -Werror=implicit-int by default, to stop regressions.

This work has some dependent changes in redhat-rpm-config and some build flag refactoring.

Owner

• Name: Carlos O'Donell
• Email: carlos@redhat.com

Current status

• Targeted release: Fedora Linux 39
• Last updated: 2023-06-27
• [url-to-devel-thread devel thread]
• Updated redhat-rpm-config: [Y] (TODO: Check if redhat-rpm-config needs updating for the new toolchain)
  • Are config.guess and config.sub up to date from upstream?
    • Needs updates for quoting: https://bugzilla.redhat.com/show_bug.cgi?id=2218011
• GCC Ada SONAME bump: [N] (TODO: Check if Ada bumped the SONAME)
  • Did we rebuild the packages in the side-tag before merging?
    • GCC 13 keeps the same SONAME. No rebuild required.
• FESCo issue: #XX
• Tracker bug: #XX
• Release notes tracker: #XX

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 13.2, before the Fedora 39 release. It contains many new features, documented here: https://gcc.gnu.org/gcc-13/changes.html. The latest point release for gcc 13 will be included in Fedora 39, this will most probably be 13.2.

The GNU Binutils version 2.40 was released before Fedora 39; and we have already been using this version of binutils in Fedora Rawhide successfully to build the distribution. Given the present schedule for Fedora 39 we will continue to use Binutils 2.40.

The GNU C Library version 2.38 is expected to be release before Fedora 39; we have started closely tracking the glibc 2.38 development code in Fedora Rawhide and are addressing any issues as they arise. Given the present schedule Fedora 39 will branch after the release of glibc 2.38. However, the mass rebuild schedule means Fedora 39 will mass rebuild (if required) before the final release of glibc 2.38, but after the ABI is frozen.

The GNU Debugger version 13.2 will be rolled out across all Fedora releases at the same time.

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 39 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; #11504

• 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.

Any source level changes required for glibc 2.38 will be noted here: https://sourceware.org/glibc/wiki/Release/2.38#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.

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 39 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 2.38 proves too disruptive to compiling the distribution we could revert to 2.37, but given that Rawhide has started tracking glibc 2.38, no show-stopper problems are expected. At this point we can still revert to upstream version 2.37 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 2.40 proves too distruptive to assembling and linking the distribution we could revert to 2.39, but given that Rawhide is using 2.40, 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 13.2 proves too disruptive to compiling the distribution we could revert to gcc 13.1.

• Contingency mechanism for gdb: If gdb 13.2 proves too disruptive to debugging the distribution we could revert to gdb 13.1.

• Contingency deadline: Fedora mass rebuild on YYYY-MM-DD.
• Blocks release?
  • No, upgrading to gcc 13.2 does not block the release.
  • Yes, upgrading to binutils 2.40 does block the release.
  • Yes, upgrading to glibc 2.38 does block the release.
  • No, upgrading to gdb 13.2 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

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

The GNU C Library version 2.38 will be released at the beginning of August 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 X.Y was released February 2023. The current release notes will be sent to the developer mailing list.