Update to GCC 6

GCC 6 is now released and is available in Debian testing. There are again the usual quirks with new standards versions and older software.

Test rebuilds of Debian testing/unstable on amd64 were done in January 2016, and bug reports filed for the packages. These issues are tracked in http://bugs.debian.org/cgi-bin/pkgreport.cgi?tag=ftbfs-gcc-6;users=debian-gcc@lists.debian.org When submitting new reports, please tag these:

User: debian-gcc@lists.debian.org
Usertags: ftbfs-gcc-6

Test rebuilds were done in Ubuntu in January 2016, covering other architectures than amd64. See the links at the bottom of the page.

Bug squashing at DebCamp/DebConf

We will have a bug squashing party at DebCamp from June 29 to July 1, core hours from 12:00 UTC until 16:00 UTC. Please join #debian-toolchain on OFTC for remote participation.

Bug squashing during DebConf will happen too, announcing the details here.

TODO list

Fixing GCC build failures.
Use GCC 6 by default.
GFortran transition (new module version).
gfortran-6 uses module version 14, the same as gfortran-5. No changes required (confirmed by Alastair McKinstry, 2016-01-23.) Work is planned to use dh-fortran-mod to capture the fortran version, but this is not required for the GCC-6 transition
Go transition (easy, no packages relying on gccgo-5).
GCJ transition (easy, a handful of dependencies).
gnat transition: In progress, contact the debian-ada ML.

Porting help

General porting help https://gcc.gnu.org/gcc-6/porting_to.html

Add pointers to porting efforts of other distributions (e.g. Fedora, OpenSUSE underway).

http://developerblog.redhat.com/2015/02/10/gcc-5-in-fedora/

Add porting recipes here.

link errors are usually caused by the new C11 inline semantics. They can be avoid by adding an attribute "__attribute__ ((gnu_inline))" before the inline keyword (preferred method), or by building with -fgnu89-inline (doesn't make sense if headers are installed in -dev packages).

Prepare for GCC 6

g++ defaults to a newer C++ standard (c++11 or c++14). Either prepare packages to build using the newer C++ standard, or explicitly pass -std=c++98 or -std=gnu++98 to the compiler for those package builds.

Timeline

TBD ...

2016-01-17: GCC 6 in experimental and bug reports filed.
2016-04-23: GCC 6.1 in unstable.
2016-07-xx: Make GCC 6 the default.

Further information

Announcements

Ubuntu test rebuild results (amd64, i386, arm64, armhf, powerpc, ppc64el, s390x):

GCC6