On Fri, 2023-01-20 at 23:11 +0000, James Le Cuirot wrote: > The context for this is a pull request I've been working on for a few weeks. > > https://github.com/gentoo/gentoo/pull/28851 > > RAP prefix nobbled gcc/clang's sysroot when invoking the linker because glibc > installed its linker scripts with prefixed paths, such as /path/to/prefix/lib > rather than just /lib. Adjusting the linker scripts rather than the compiler > behaviour is more natural and makes cross-compiling far easier. > > For the migration procedure, I did try a different approach of manually fixing > up the linker scripts, but if you do this first, the gcc build fails > immediately, and if you do this afterwards, the gcc build fails later. A > symlink is therefore needed to allow the sysroot to be applied, even when the > linker script paths are still prefixed. > > Unfortunately, it's not possible to filter news items on USE flags or even > profile parents, so I've had to resort to explicitly listing all the prefix > profiles. Prefix is quite a niche feature, so I don't want to show this news > to everyone.
Following some feedback elsewhere, I'm going to add an additional paragraph,
because many users are not sure what kind of prefix they have. See below.
> ----
>
> Title: Breaking changes to the RAP Prefix toolchain
> Author: James Le Cuirot <ch...@gentoo.org>
> Posted: 2023-01-20
> Revision: 1
> News-Item-Format: 2.0
> Display-If-Profile: default/linux/amd64/17.0/no-multilib/prefix/*
> Display-If-Profile: default/linux/amd64/17.1/no-multilib/prefix/*
> Display-If-Profile: default/linux/amd64/23.0/no-multilib/prefix/*
> Display-If-Profile: default/linux/amd64/23.0/split-usr/no-multilib/prefix/*
> Display-If-Profile: default/linux/arm/17.0/armv7a/prefix/*
> Display-If-Profile: default/linux/arm/23.0/armv7a/prefix/*
> Display-If-Profile: default/linux/arm/23.0/split-usr/armv7a/prefix/*
> Display-If-Profile: default/linux/arm64/17.0/prefix/*
> Display-If-Profile: default/linux/arm64/23.0/prefix/*
> Display-If-Profile: default/linux/arm64/23.0/split-usr/prefix/*
> Display-If-Profile: default/linux/ppc64le/17.0/prefix/*
> Display-If-Profile: default/linux/riscv/20.0/rv64gc/lp64d/prefix/*
> Display-If-Profile: default/linux/riscv/23.0/rv64/lp64d/prefix/*
> Display-If-Profile: default/linux/riscv/23.0/rv64/split-usr/lp64d/prefix/*
> Display-If-Profile: default/linux/x86/17.0/prefix/*
> Display-If-Profile: default/linux/x86/23.0/prefix/*
> Display-If-Profile: default/linux/x86/23.0/split-usr/prefix/*
>
> We are changing the way the toolchain operates on RAP Prefix systems in order
> to
> reduce the number of hacks we need to apply and make cross-compiling easier.
>
> If you using a non-RAP "Prefix Guest" or "Prefix Stack" variant (e.g. macOS)
> then this does not apply.
If you're not sure what kind of prefix you have, then check whether the
prefix-guest USE flag is enabled.
portageq envvar USE | grep prefix-guest
> If you are using a libc other than glibc (e.g. musl) then this *does* apply,
> but
> your libc will *not* break, so you should not carry out the following
> procedure.
> The only other package known to be affected is dev-libs/libbsd, which you can
> simply update. If you find another package affected by this, then please file
> a
> bug report.
>
> WARNING! It is important that you carry out the following procedure, otherwise
> your toolchain will break when you next update your compiler or glibc.
>
> 1. Run the following to create a temporary symlink:
>
> EPREFIX=$(portageq envvar EPREFIX)
> mkdir -p "${EPREFIX}${EPREFIX%/*}"
> ln -sn "${EPREFIX}" "${EPREFIX}${EPREFIX}"
>
> 2. Update or rebuild all installed slots of sys-devel/gcc and
> sys-devel/clang
> (if any). Feel free to remove any you no longer need.
>
> 3. Update or rebuild sys-libs/glibc.
>
> 4. Run the following to remove the symlink:
>
> EPREFIX=$(portageq envvar EPREFIX)
> rm "${EPREFIX}${EPREFIX}"
>
> 5. If dev-libs/libbsd is installed, then update it to 0.11.7-r2 or later.
>
> If you are reading this having updated glibc first and you are no longer able
> to
> build anything, then don't panic. Simply execute the line below and then carry
> out the regular procedure above.
>
> qlist sys-libs/glibc | xargs grep -lIF "GNU ld script" | xargs sed -i -r
> "s: /(usr|lib): $(portageq envvar EPREFIX)/\1:g"
>
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