F21 System Wide Change: GCC49

[Jaroslav Reznik]

= Proposed System Wide Change:  GCC49 =
https://fedoraproject.org/wiki/Changes/GCC49

Change owner(s): Jakub Jelínek <jakub at redhat.com > 

Switch GCC in Fedora 21 to 4.9.x, rebuild all packages with it. 

== Detailed Description ==
GCC 4.9.0 is currently in stage4, in prerelease state with only regression 
bugfixes and documentation fixes allowed. The release will happen probably in 
the first half of April. Marek Polacek has performed a test mass rebuild on 
x86_64 with gcc-4.9.0-0.*.fc21, most packages have built successfully, others 
have failed to rebuild also with gcc 4.8.x, for the remaining packages most of 
the needed changes are now tracked in [1] or, if it were bugs on the gcc side, 
have been fixed in the mean time. GCC 4.9.0 prereleases have so far been built 
as scratch packages, [2]  (and similarly for ppc* and s390* secondary 
architectures). Other distributions have performed test mass rebuilds on other 
architectures (i?86, s390x, arm). 

== Scope ==
All packages should be rebuilt with the new gcc once it hits f21.

* Proposal owners:  Build gcc in f21, rebuild packages that have direct 
dependencies on exact gcc version (libtool, llvm, gcc-python-plugin).
* Other developers: First few days/weeks just voluntary rebuilds using the new 
system gcc, if things fail, look at http://gcc.gnu.org/gcc-4.9/porting_to.html 
and fix bugs in packages or, if there is a gcc bug or suspected gcc bug, 
analyze and report. 
* Release engineering: Organize a mass rebuild 
* Policies and guidelines: No policies need to be changed 

---
Change Wrangler Note: Contingency Deadline is a bit vague "Before release" but 
with GCC revert, distribution wide coordination would be needed with high 
probability of slip. I'll open it for further discussion on list for 
FESCo/releng..

[1] http://gcc.gnu.org/gcc-4.9/porting_to.html 
[2] http://koji.fedoraproject.org/scratch/jakub/task_6667028/