[Buildroot] [PATCH 2/2] package/libv4l: link with libatomic when needed

[Peter Seiderer <ps.report@gmx.net>]

Hello *,

On Wed, 20 Nov 2019 14:46:03 +0000, Thomas Preston <thomas.preston@codethink.co.uk> wrote:

> Hey,
>
> On 30/10/2019 22:26, Peter Seiderer wrote:
> > Adding the (missing?) '-L/home/seiderer/Work/Buildroot/build_sparc_qt5multimedia_001/host/bin/../sparc-buildroot-linux-uclibc/sysroot/usr/lib'
> > libtool command line parameter fixes the linking for the actual build...
> >
> > Any hint which (buildroot?) change triggered the remove of the link/library path removal?
> >
>
> As previously discussed [0], the missing `-L..` is because pkgconf no longer
> returns "system" include or library directories with -I and -L  (see [1]).
> These are already in the compiler's default search path and were causing
> include-order related bugs when using -isystem.
>
> However, it looks like that change has caused a problem here, where the output
> from pkgconf is being passed to libtool to point it at the "system" library
> directory in the sysroot.
>
> I don't know enough about libtool yet, but I think there are a few ways around
> this:
> 1. Tell libtool where the sysroot is by some other mechanism
> 2. Tell pkgconf that we want to keep the system lib directories, when it is
>    used to create arguments to libtool. The following argument will always
>    return -L, as expected above:
>
>         pkg-config --keep-system-libs

The libv4l/libatomic case can be fixed by the following (hack):

diff --git a/package/libv4l/libv4l.mk b/package/libv4l/libv4l.mk
index a3bf099221..46c1ab9a48 100644
--- a/package/libv4l/libv4l.mk
+++ b/package/libv4l/libv4l.mk
@@ -16,7 +16,7 @@ LIBV4L_AUTORECONF = YES
 LIBV4L_DEPENDENCIES += host-gettext

 # fix uclibc-ng configure/compile
-LIBV4L_CONF_ENV = ac_cv_prog_cc_c99='-std=gnu99'
+LIBV4L_CONF_ENV = ac_cv_prog_cc_c99='-std=gnu99' PKG_CONFIG_SYSROOT_DIR=$(STAGING_DIR)

 # v4l-utils components have different licences, see v4l-utils.spec for details
 LIBV4L_LICENSE = GPL-2.0+ (utilities), LGPL-2.1+ (libraries)

Regards,
Peter

>
> I'm looking into this, but someone with a more intimate knowledge of libtool +
> pkg-autotools.mk, might be able to help here.
>
> Thanks,
> Thomas Preston
>
> [0] http://lists.busybox.net/pipermail/buildroot/2019-November/266369.html
> [1] http://lists.busybox.net/pipermail/buildroot/2019-October/263178.html
>