[Buildroot] [PATCH 3/3] pkgconf: Configure using pkgconf-personality

[Arnout Vandecappelle]

On 12/10/2019 22:09, Thomas Petazzoni wrote:
> On Sat, 5 Oct 2019 15:43:36 +0200
> Arnout Vandecappelle <arnout at mind.be> wrote:
> 
>>  I think the personality approach is better than the wrapper script for sure.
>> However, it's not always easy to override a package's idea of how to call
>> pkg-config (e.g. quite a few use `pkg-config ...` in the Makefile directly - in
>> fact, we do the same, in support/kconfig!). Therefore, I think a better approach
>> is to have a separate "host" and "cross" bin directory, both of which contain a
>> pkg-config (symlink or wrapper script). For cross-compilation, both directories
>> are put in PATH, and for host compilation on the host directory.
> 
> I already expressed my opinion on this before, but I think the
> pkg-config vs. TUPLE-pkg-config solution is the right thing to do. It
> is really the standard way of doing this, the PKG_CHECK_MODULES()
> autoconf macro looks first for TUPLE-pkg-config, before using
> pkg-config.
> 
> Yes, it's not going to work with a number of packages that directly use
> "pkg-config", but they should "simply" be fixed, no?

 True. But I think in Buildroot we generally try to be pragmatic, and prefer a
single solution that fixes things for all packages instead of fixing each and
every package individually. At least, if this can be done in a relatively simple
way.


> Another problem with the approach you suggest is that some packages
> build both target code and host code. In this case, playing around with
> two pkg-config binaries installed in two different locations isn't
> going to work well. While with different names, you can have PKG_CONFIG
> and PKG_CONFIG_FOR_BUILD with different values.

 For those cases, it's equally broken at the moment since there's no way to tell
the package that it needs different PKG_CONFIG_LIBDIR for host build. So we need
to do something there...

 Of course, we could use the best of both worlds: use the TUPLE-pkg-config and
make the cross-dir pkg-config a symlink to it (or wrapper script, if
TUPLE-pkg-config can use personality completely).

>>  The cross dir can then also be populated with the -config script from
>> STAGING_DIR, which avoids having to pass them explicitly in other packages.
> 
> That is admittedly an interesting argument.

 That was in fact my original motivation to think of this cross dir, and then I
realized the same could solve the pkg-config issue.

 Regards,
 Arnout