[gentoo-dev] Re: Monthly x11@ project status for May 2018

[Mike Gilbert]

On Mon, May 7, 2018 at 4:49 PM, Matt Turner <mattst88@g.o> wrote:
> On Mon, May 7, 2018 at 1:38 PM, Matt Turner <mattst88@g.o> wrote:
>> == Convert media-libs/mesa ebuild to build with Meson ==
>> https://bugs.gentoo.org/652762
>>
>> Ebuild posted. Blocked on problems surrounding LLVM (this is the story of
>> maintaining media-libs/mesa).
>>
>> The problem is that Meson has no way of specifying a different llvm-config
>> binary without a cross file, which our meson.eclass does not generate for
>> 32-bit x86 builds on amd64. We've filed a Meson issue here [4] but haven't
>> seen
>> any progress towards a solution.
>
> Just wanted to highlight this section for the Meson maintainers specifically.
>
> Why do we not generate cross files for 32-bit builds on 64-bit? As far
> as I understand that would be sufficient for us. Do you have any
> suggestions?

Using a cross file triggers cross-compile mode in meson, which makes
it behave differently in some ways. It is hard to say exactly what the
differences are; this aspect of meson if very poorly documented.

As an experiment, I implemented some changes in meson.eclass to have
it always use a cross file.

https://github.com/gentoo/gentoo/pull/8379

This seems to work ok for building systemd with multilib enabled.

Once difference I spotted is that the CFLAGS/LDFLAGS given in the
cross file get appended at the end of the compile/link commands,
instead of in the middle. That could be problematic since link
arguments like --as-needed are sensitive to their position on the
command line.

Anyway, it would be great if meson would just look at the LLVM_CONFIG
environment var instead of forcing us to use a cross file here.