[Buildroot] [PATCH v2 00/12] Add the support for Clang cross-compiler

Arnout Vandecappelle arnout at mind.be
Sat Aug 29 18:53:23 UTC 2020

 Hi Romain,

 After almost a year, let's try to make some progress on this series :-)

On 07/09/2019 11:40, Romain Naour wrote:
> Recently, I've tried to build an aarch64 Linux kernel (5.2.7) with
> Clang and it worked under Qemu [3]. I also tested for x86_64 but we need
> the upcomming llvm/clang version 9 to build the kernel [4].

 Since we waited long enough, this is now in Buildroot :-)

> This new version add the support of "asm-goto" which was the last
> missing part to be able to build the Linux kernel on x86_64 [5].
> But for theses tests, only the kernel was built with Clang.
> While testing the x86_64 kernel and it's rootfs built with Clang under Qemu,
> I had a runtime issue during the userspace boot process (Busybox's init).
> While searching about the issue, I discover the lowRISC blog from Luís Marques
> about the same issue and tested the patch he contributed to the Busybox project
> (Thanks!).
> So, this series is about to complete the integration of Clang as cross-compiler
> by using a toolchain-wrapper and fixing some build system infrastructure
> (cmake, meson) to use Clang instead of GCC.

 I started integrating the series, but then I had some fundamental problems with
the core patch itself. So I stopped and pushed my results to
https://gitlab.com/arnout/buildroot branch clang-as-cross-compiler. I put my
changes as squash patches rather than changing the original patches, so you can
easily take over from there. Note that I haven't tested my rebased and modified
branch (just a build test immediately after applying the modified patch), so
there may still be some rebase f**up there.

 I'll put my feedback in the individual patches.


> Add this new experimental option into "Advanced" menu since we are expecting
> some build and runtime issues for number of packages (bootloaders, kernel).
> For now, Clang cross-compiler can only be use as internal toolchain,
> so it is build from the source which take a long time...

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