Profile 23 success story

[Goverp]

My system is AMD64, using OpenRC and split /usr. I build in a chroot which creates binpkgs, and then install onto my target machines using those binpkgs.
As the final step of the profile 23 movesinvolves "emerge --emptytree @world", I decided to incorporate other changes I was planning:

• Move to clang; I've been doing this piecemeal for ages, so I already have a small list of packages that require gcc.
  
• Move to LTO everywhere; again I've done this for a few packages, but now I decided to try it as default;
  
• Move to the Mold linker. I played with it in the early days, but it broke things so I stopped. But more recently I found it working where the default linker failed, so I thought what the heck? Again, I had a very small list of things that required other linkers.

This is obviously aggressive/optimistic...
It worked fine, taking about 7 hours for my ~1,400 packages, on my 16 core Zen3 processor. A few more packages turned out to need gcc. System up and running. I ran "qlop -r" in a loop while compiling, and the estimated time to completion tended to be about twice the time the various compilations actually took - not sure if the LTO'd gcc and clang were much faster or just my emerge.log contains several years of historical compilations on slower hardware to bias qlop's calculations.

(See the wiki items on Mold, LTO and Clang for details if necessary.)

One minor problem was busybox won't build on kernel 6.8 due to changes in the network stack. It's a known and reported problem, and the bypass is to remove "CONFIG_TC=y", so that was a learning experience on savedconfig and configuring busybox (cd to /var/tmp/portage/sys-apps/busybox/work, edit .config to remove the errant setting, run "make oldconfig" to tidy up the pieces, and copy the resulting .config to /etc/portage/savedconfig/sys-apps/busybox-foo-bah).

I repeated the instructions for the installation using the binpkgs, apart, of course, for deleting /var/cache/binpkgs, which would have been a bit awkward! I suspect there's no need to take the separate steps to rebuild gcc, glibc and libtool, as they were already built correctly, but I did them anyway just in case. Again no problem, apart from finding that something wanted an old copy of something (I forget what) which broke the "emerge -e", and I forgot to add "--resume --keep-going" when I restared, so I reinstalled about 500 packages twice, which was a waste of an hour...
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Greybeard