F22 System Wide Change: GCC5

[Jaroslav Reznik]

= Proposed System Wide Change: GCC5 =
https://fedoraproject.org/wiki/Changes/GCC5

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

Switch GCC in Fedora 22 to 5.x.y, rebuild all packages with it.

== Detailed Description ==
GCC 5 is currently in stage3, but in 3 days will move to stage4, in prerelease 
state with only regression bugfixes and documentation fixes allowed. The release 
will happen probably in the first half of April. We are working on scratch gcc 
rpms and will perform a test mass rebuild. Other distributions have performed 
test mass rebuilds already. 

== Scope ==
All packages should be rebuilt with the new gcc once it hits f22.

* Proposal owners: Build gcc in f22, 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-5/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 

== Contingency Plan ==
If bugs are discovered, I'd appreciate help from the package owners in 
preparing self-contained testcases to speed up analysis and fixing the bugs. 
Don't have time to debug issues in 12000+ packages, especially when in many 
cases it could be caused by undefined code in the packages etc. I don't expect 
we'll have to fall back to the older gcc, we've never had to do it in the 
past, but worst case we can mass rebuild everything with older gcc again.

* Contingency mechanism: Revert to older gcc, mass rebuild everything again
* Contingency deadline: Before release
* Blocks release? Yes
* Blocks product? No