https://fedoraproject.org/wiki/Changes/GNUToolchainF39


This document represents a proposed Change. As part of the Changes
process, proposals are publicly announced in order to receive
community feedback. This proposal will only be implemented if approved
by the Fedora Engineering Steering Committee.


== 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.

Bug: https://bugzilla.redhat.com/show_bug.cgi?id=2218018

=== Enable warnings ===

Early work for Fedora 40's
[https://fedoraproject.org/wiki/Changes/PortingToModernC 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.

Bug: https://bugzilla.redhat.com/show_bug.cgi?id=2218019

== Owner ==

* Name: [[User:codonell|Carlos O'Donell]]

* Email: car...@redhat.com


== 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 has already been 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. <!-- What work
do the feature owners have to accomplish to complete the feature in
time for release?  Is it a large change affecting many parts of the
distribution or is it a very isolated change? What are those
changes?-->

* 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;
[https://pagure.io/releng/issue/11504 #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 ==

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 test suite which is run during
the package build and examined by the gcc developers before being
uploaded.

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

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


== User Experience ==


<!-- TODO: Talk about any new GNU Toolchain user experience updates. -->

== 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.

* 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.






-- 
Aoife Moloney

Product Owner

Community Platform Engineering Team

Red Hat EMEA

Communications House

Cork Road

Waterford
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