My experience: gcc-5 usable by now

[mv]

According to my experience switching to gcc-5 is what can now be done even on production systems:

I am running all of my systems (amd64 and x86) compiled completely with gcc-5.1 for quite a while now; the last problem I had was resolved with the release of gcc-5.2: If qtwebkit is compiled with gcc-5.2 (instead of gcc-5.1), skype will no longer crash.

For comparison: My systems are rather complete desktops, including libreoffice, full texlive (2014 and now even 2015), and a lot of math applications. (Be aware that I use neither gnome nor kde; however, in the German forum full kde (4 and 5) were reported to work flawlessly with gcc-5.1, too. I suppose - though I didn't try - that gnome shouldn't be a problem, either).

Things to be aware of:

• Compile the whole system with gcc-5: Compiling only part of the system calls for trouble due to the changed ABI. This is the most important point. If you observe this and run carefully a full emerge -e @world (observing the points below) almost nothing can go wrong. eix-installed-after -b ... is your friend...
  
• Some packages need to be ~amd64 or ~x86 to compile.
  
• Very few packages need in addition a patch to compile; however, all patches I needed are contained in the gentoo bugzilla and can all be found over the gcc-5 tracker bug (most of these patches are meanwhile in the gentoo repository anyway).
  
• I used flto only where it compiled out-of-the-box (I did not attempt to patch binutils or switch to gold in case of problems). Besides compilation issues, I had only one problem with flto on gcc-5 so far: If icu is compiled with flto then libreoffice will not compile on x86 (it does on amd64, though).
  
• I did not try graphite, because I had bad experience with it (subtle crashs and instabilities) from previous gcc versions.

[VoidMage]

If we're talking about the same binutils patch, it's already included in binutils 2.25, you just need a symlink then.

Still, any chance you've tested wine ? I known it was miscompiled by 5.1...

In fact, it seems that there's still a bug that affects it, that's fixed on the 5 branch, but not yet in 5.2 (unless gcc maintainers imported the fix).

[mv]

[mv]

[nlsa8z6zoz7lyih3ap]

Inspired by this topic I have suucessfully upgraded to gcc-5.2 with kde. The result does seem to be stable enough for production use.
Here are some points about this upgrade.

(1) In order to compile kde I upgraded to "~amd64". Not everything in kde-meta compiles, but everything in my working desktop selected with sets of my choice does and, as far as I can see, works just fine.

(2) xemacs and wine did not compile with gcc-5.2 so I recompiled them with gcc-4.9.3 and they seem to work just fine on this system.

(3) the upgrade from gcc-4.9.3 to gcc-5.2 was not seamless the way that it was from 4.7 to 4.9 . However, with a little persistance I was able to succeed.

I always enjoy trying things like this. Except for the fun of it, I don't think that the effort was worth it in any practical sense, so I don't really recommend it to anyone else yet, except to point out that if you want to try it the result works very well indeed. (I tried this with gcc-5.0 and had no success whatsoever.)

(4) I always have two working partitions of "/" so it will be painless to reutrn to gcc-4.9.3 and "amd64" now that I have had my fun.

I used no special patches or overlays.

[nlsa8z6zoz7lyih3ap]

My system with gcc-5.2 as described above hung when shutting down from kde and required a hard reset. Perhaps this is because traces of gcc-4.9 remained on the system.
Thus, in my case, gcc-5.2 is not yet ready for production use.

[Buffoon]

emerge -e @system, 35 packages didn't build with gcc-5.2.0.

[mv]

[mv]

[Buffoon]

Thanks, will create that toolchain set. Is isl still used by gcc-5.2.0?

[nlsa8z6zoz7lyih3ap]

[schorsch_76]

@mv: Thanks for that thread! In deed i was thinking to switch to gcc 5.2 too! Now a backup is running on my laptop and i prepare to switch to it
_________________
// valid again: I forgot about the git access. Now 1.2GB big. Start: 2015-06-25
git daily portage tree
Web: https://github.com/schorsch1976/portage
git clone https://github.com/schorsch1976/portage

[mv]

[Buffoon]

[mv]

[Buffoon]

Thanks! My bad, should have written dev-libs/isl.

[Ormaaj]

Graphite seems usable for the most part. I just rebuilt everything on one system with gcc-5.2 and graphite. I noticed a marked increase in the number of graphite-related failures compared to 4.9.3 (up from virtually zero to around 50).

[schorsch_76]

Here at my laptop the following packages failed to build:

[mv]

[mv]

[schorsch_76]

I got the following with patches building with gcc-5.2.0.

# preprocessor patch "-P"
x11-apps/sessreg-1.1.0:0/0::gentoo #546742
dev-libs/libgpg-error-1.13::gentoo #555820

# out of memory error / tmpfs
# fix: cleanup /var/tmp/portage
mail-client/thunderbird-31.8.0
media-gfx/inkscape-0.48.5-r1

The other packages i need to find out the reasons. I got notes and read through the gcc porting guide.

Edit: todays portage update fixed for me
- sys-block/thin-provisioning-tools as it upgraded to 0.4.x
_________________
// valid again: I forgot about the git access. Now 1.2GB big. Start: 2015-06-25
git daily portage tree
Web: https://github.com/schorsch1976/portage
git clone https://github.com/schorsch1976/portage

[mv]

[schorsch_76]

@mv: Yes of course, not gcc specific, but the reason was the tmpfs.

Now i am down to 4 packages which dont build with gcc-5.2.
bmon
llvm
kicad
xorg-server

llvm: I dont want to ~arch it, because mesa blocks <3.6 llvm. So i Keep it until a new mesa arrives.
The other tools i will add a project specific conf to use gcc 4.9 until they arrive at a version which builds under gcc 5.2

about xorg-server ... i am not sure if i want to go to ~arch. Right now i have under 10 ~arch packages....

right now the whole "world" gets rebuild to check all again.
_________________
// valid again: I forgot about the git access. Now 1.2GB big. Start: 2015-06-25
git daily portage tree
Web: https://github.com/schorsch1976/portage
git clone https://github.com/schorsch1976/portage

[mv]

[jean-michel.smith]

For those who need java with gcc-5.2.0 (I do for certain remote consols), icedtea-7.2.6.1 from the java overlay compiles and runs fine in a gcc-5.2.0 environment. This was the only blocker for my desktop.