Clang/LLVM as a main toolchain for Gentoo Linux!

WARNING: Alpha quality!

This is Gentoo Linux overlay experiment allowing to have your stage3 completely GCC-free. You can either grab a release and process with installation as per Gentoo Handbook, or try to switch your current system profile and rebuild world.

Available profiles

ppc

• clang based on default/linux/ppc/17.1;
• clang/lto same, but with LTO;
• clang/musl based on default/linux/ppc/17.0/musl;
• clang/musl/lto same, but with LTO.

NOTE

bootstrap profile is used by catalyst only and shouldn't be selected.

HOWTO

Add this overlay

eselect repository add toolchain-clang git https://github.com/2b57/toolchain-clang.git
emaint sync -r toolchain-clang

How to use it

This is your default stage3 + git + eselect-repository packages for overlay management. You'll get warnings that your profile symlink is invalid, so after chrooting inside be sure to add this overlay (see above) and select right profile:

# eselect profile list | grep toolchain-clang:linux/ppc/clang/musl
  [43]  toolchain-clang:linux/ppc/clang/musl (exp)
  [44]  toolchain-clang:linux/ppc/clang/musl/lto (exp)
# eselect profile set --force 43
# eselect profile list | grep toolchain-clang:linux/ppc/clang/musl
  [43]  toolchain-clang:linux/ppc/clang/musl (exp) *
  [44]

I want to build stage3 myself

Overview

Apart from custom spec files, some modifications to scripts/bootstrap.sh are required. In order to execute right file, provided build script creates OverlayFS mount which will be used as Gentoo Portage tree for catalyst; contents of /var/db/repos/gentoo (main tree) is combined with assets/baserepo_overlay folder. Catalyst envscripts (catalystrc) are created as needed during the process.

bootstrap profile

bootstrap profile is used for building stage1 with GCC if there are no seed clang stages available and should not be explicitly chosen. In this case, catalyst build order is bootstrap-stage1 -> clang-stage2 -> clang-stage3. If clang seed stage is present, you'll need to edit spec files accordingly.

musl

If you want to go with anything musl-related, you'll need to clone RelEng repo as well, since musl stages require some of the tweaks from there:

cd /var/db/repos/toolchain-clang
git clone https://github.com/gentoo/releng.git

Building

• Add this overlay to your system (see above)
• Install deps: catalyst and pixz
• Pick a profile, but don't eselect it
• Run stage-builder.sh script against corresponding spec file:

cd /var/db/repos/toolchain-clang
./assets/scripts/stage-builder.sh specs/clang/musl/stage1.spec
./assets/scripts/stage-builder.sh specs/clang/musl/stage2.spec
./assets/scripts/stage-builder.sh specs/clang/musl/stage3.spec