[oe] Preferred handling of pkg-config in cross compile environments.

[Chris Larson]

On Sun, Oct 10, 2010 at 10:38 AM, Paul Menzel <
paulepanter at users.sourceforge.net> wrote:

> Am Sonntag, den 10.10.2010, 10:09 -0700 schrieb Chris Larson:
> > On Sun, Oct 10, 2010 at 10:05 AM, Paul Menzel <
> > paulepanter at users.sourceforge.net> wrote:
> >
> > > I stumbled upon several programs who call plain `pkg-config` [1][2].
> > >
> > > Is the following statement correct?
> > >
> > > To be able to cross compile programs correctly, the build files are
> > > supposed to use the environment variable `PKG_CONFIG` and only call
> > > pkg-config directly if `PKG_CONFIG` is empty.
> > >
> > >        if test -z "${PKG_CONFIG}"; then
> > >            PKG_CONFIG="pkg-config"
> > >
> > > If you agree I would note that somewhere in the Wiki, so that upstream
> > > can be pointed to some documentation and search the Web will result in
> > > some useful results.
> > >
> >
> > Can you explain why running just 'pkg-config' is a problem?  It seems to
> > work just fine..
>
> Do you have a minimal build host. Some problems do not surface if some
> files are installed locally on the build host.
>
> Please take a look at [2] I forgot to add in my original message. I have
> no clue why the staged(?) pkg-config behaves differently than the local
> installed one. Does it search the paths in a different order?
>

pkgconfig-native searches its own built in path (the one in the native
sysroot) along with the paths in PKG_CONFIG_PATH.  None of those are outside
of the sysroots.

Secondly I am having a similar problem with `gobject-introspection`
> where [1]
>
>        gir/Makefile.am:GLIB_INCLUDEDIR=$(shell pkg-config
> --variable=includedir glib-2.0)/glib-2.0
>        gir/Makefile.am:GLIB_LIBDIR=$(shell pkg-config --variable=libdir
> glib-2.0)
>
> returns the wrong path.
>
>        Making all in gir
>        make[2]: Entering directory
> `/oe/build-minimal-libc/minimal-dev/work/armv7a-oe-linux-gnueabi/gobject-introspection-0.9.12-r0/gobject-introspection-0.9.12/gir'
>        make[2]: *** No rule to make target
> `/usr/lib/glib-2.0/include/glibconfig.h', needed by `GLib-2.0.gir'.  Stop.
>        make[2]: Leaving directory
> `/oe/build-minimal-libc/minimal-dev/work/armv7a-oe-linux-gnueabi/gobject-introspection-0.9.12-r0/gobject-introspection-0.9.12/gir'
>        make[1]: *** [all-recursive] Error 1


/usr/{lib,include} paths are mangled by pkg-config using
PKG_CONFIG_SYSROOT_DIR.  If that's not happening here, that's a bug that
should be investigated, but I fail to see how setting PKG_CONFIG is going to
magically fix it.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics