Re: [PATCH] build: fix build on FreeBSD with Meson 0.61.1

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Feb 14, 2022 at 12:43:13PM +0100, Karl Bonde Torp wrote:
> When building with Meson 0.61.1 on FreeBSD some archives become
> corrupted. This can be avoided by using 'llvm-ar' instead of 'ar'.
> 
> Signed-off-by: Karl Bonde Torp <k.torp@samsung.com>
> ---
>  buildtools/meson.build | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/buildtools/meson.build b/buildtools/meson.build
> index 400b88f251..e1c600e40f 100644
> --- a/buildtools/meson.build
> +++ b/buildtools/meson.build
> @@ -31,6 +31,9 @@ if host_machine.system() == 'windows'
>          pmdinfo += 'llvm-ar'
>      endif
>      pmdinfogen += 'coff'
> +elif host_machine.system() == 'freebsd'
> +    pmdinfo += 'llvm-ar'
> +    pmdinfogen += 'elf'
>  else
>      pmdinfo += 'ar'
>      pmdinfogen += 'elf'
> -- 

Based off the instructions you posted later in the thread, I've reproduced
the issue - and then done a little extra investigation. Here is my
understanding:

* By default on FreeBSD the linking is being done by llvm-ar
* The resulting libraries are being linked as thin archives and "ar" binary
  does not seem to be able to process them.
* When building with CC=gcc on FreeBSD, "ar" is used as a linker, and the
  resulting archives are regular .a files.
* On Linux, whether building with clang or gcc, "ar" seems to be used as
  linker.

The ideal situation here would be if we could use meson to report itself
what the static linker in use is, but unfortunately while we can query the
dynamic linker using "meson.compiler().get_linker_id()", there doesn't seem
to be an equivalent for the static linker. Therefore, the only option seems
to be a fix as here. Only question remains as to whether we want to only
use llvm-ar for clang builds on FreeBSD or use if for all builds on FreeBSD.
I'm not sure it makes much difference either way, but I'd tend towards
limiting the use of llvm-ar to only clang builds.

With or without this suggested change,

Acked-by: Bruce Richardson <bruce.richardson@intel.com>