== Summary ==
Update the Fedora 36 GNU Toolchain to gcc 12 and glibc 2.35.
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.
Reading through the GCC 12 changes, there is a significant new feature to GCC
that would appear to be useful for security. There is a new:
flag that initializes all stack variables to zero. Zero being a nice safe
value that makes programs crash instead of being exploitable.
Are there plans to enable this flag so that all applications, but more
importantly the kernel, are hardened against uninitialized stack variables?
This is one of the major classes of security bugs that could potentially be
eliminated during this mass rebuild.
== Owner ==
* Name: [[User:submachine| Arjun Shankar]]
* Email: arjun(a)redhat.com
== 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 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 12 in Q2,
before the Fedora 36 release. It will contain 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) before the final release of
glibc 2.35, but after the ABI is frozen.
The GNU Binutils version 2.37 and GNU Debugger version 11.1 currently
included in Fedora 35 will continue to be included in Fedora 36. There
will be a GNU Binutils version 2.38 released at the end of January,
but the inclusion will be scheduled for Fedora 37.
== 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
== 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 36 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. An update
to GCC 12.1 would mean a new major release and could have broad scope
* Release engineering: 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
[[Changes/RemoveNSCD|removal of nscd]].
Some source changes may be required for gcc 12 rebase:
== 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
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.
== User Experience ==
Users will see improved performance, many bugfixes and improvements to
POSIX compliance, Unicode 14 support, C.UTF-8 locale support, improved
experimental support for C++20 and C++23, new compiler warnings and
improvements to existing ones, and more.
== Dependencies ==
<!-- What other packages (RPMs) depend on this package? Are there
changes outside the developers' control on which completion of this
change depends? In other words, completion of another change owned by
someone else and might cause you to not be able to finish on time or
that you would need to coordinate? Other upstream projects like the
kernel (if this is not a kernel change)? -->
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. The mass rebuild would ensure all packages can be
built with the newer compiler and core runtime.
== Contingency Plan ==
* Contingency mechanism glibc: If glibc 2.35 proves 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 mechanism for gcc: If gcc 12 proves too disruptive to
compiling the distribution we could revert to gcc 11.
* Contingency deadline: Fedora mass rebuild on 2022-01-19.
* Blocks release? Yes, upgrading to the gcc 12 release blocks the
release. Yes, upgrading to glibc 2.35 does block the release.
== Documentation ==
The gcc 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.
== Release Notes ==
The GNU Compiler Collection version 12 is soon to be released. See
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
He / Him / His
Fedora Program Manager
devel mailing list -- devel(a)lists.fedoraproject.org
To unsubscribe send an email to devel-leave(a)lists.fedoraproject.org
Fedora Code of Conduct:
g Do not reply to spam on the list, report it: