[Buildroot] [PATCH 1/1] package/pkg-meson: use pkgconf to find host libraries.

[James Hilliard]

On Sun, Feb 2, 2020 at 2:47 AM Arnout Vandecappelle <arnout at mind.be> wrote:
>
>  Hi Nicolas,
>
>  Looks good to me, but...
>
> On 30/01/2020 09:47, Nicolas Cavallari wrote:
> > meson makes a distinction between 'native' (i.e. host) dependencies
> > and 'host' (i.e. target) dependencies and can use a different pkg-config
> > binary for each case.
> >
> > Currently, pkg-meson only pass the target pkg-config and meson
> > automatically guesses the host pkg-config by searching PATH, which finds
> > host/bin/pkg-config, which is the target pkg-config wrapper script.
> >
> > As a result, meson uses the target pkg-config to find host dependencies,
> > with possibly incorrect results.
> >
> > This patch causes meson to use host/bin/pkgconf directly to find host
> > dependencies, using the apparently recommended method[1] of
> > specifing the PKG_CONFIG environment variable.  pkgconf does not know
> > about the target sysroot, so only finds host dependencies.
>
>  In HOST_MAKE_ENV we also set
>
> PKG_CONFIG_LIBDIR="$(HOST_DIR)/lib/pkgconfig:$(HOST_DIR)/share/pkgconfig"
>
> Don't we still need that to make sure it will indeed find our own .pc files? Or
> is that anyway the default for pkgconf due to our --prefix in the configure step?
Meson provides a command line flag to correctly set the pkg-config
libdir path for
only dependencies with native: true, this would not do that correctly from my
understanding as the PKG_CONFIG_LIBDIR would need to be scoped to
dependencies with native: true.
See my patch here fixing this:
https://patchwork.ozlabs.org/project/buildroot/patch/20200428122213.63826-1-james.hilliard1@gmail.com/
>
>  Similar for
>
> PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1
> PKG_CONFIG_ALLOW_SYSTEM_LIBS=1
>
> although for those I do think they're not needed.
>
>  Regardless, I think it would be cleaner to create a
> $(HOST_DIR)/bin/host-pkg-config wrapper that sets the environment correctly for
> the host.
Since we set pkgconfig = '@HOST_DIR@/bin/pkgconf' in our cross-compilation.conf
we only need to set the host libdir for building native: true
dependencies, my patch
fixes that issue properly so this sort of workaround should not be necessary.
>
>
>  Regards,
>  Arnout
>
> >
> > [1] https://github.com/mesonbuild/meson/issues/1849
> >
> > Signed-off-by: Nicolas Cavallari <nicolas.cavallari at green-communications.fr>
> > --
> >
> > This meson.build snippet:
> >
> > ----------------------------
> > host_glib = dependency('glib-2.0', native: true, method: 'pkg-config')
> > gdbus_codegen = find_program(host_glib.get_pkgconfig_variable('bindir')
> >                              + '/gdbus-codegen')
> > ----------------------------
> >
> > Without the patch, it uses the target .pc file with a prefix of /usr,
> > and finds /usr/bin/gdbus-codegen from the host :
> >
> > Found pkg-config: $OUTPUT/host/bin/pkg-config (1.6.1)
> > Build-time dependency glib-2.0 found: YES 2.62.4
> > Program /usr/bin/gdbus-codegen found: YES (/usr/bin/gdbus-codegen)
> >
> > For a complete dummy example, use this dummy package:
> >
> > base64 -d << EOF | tar -xJv
> > /Td6WFoAAATm1rRGAgAhARwAAAAQz1jM4Cf/AsJdADgYSJnNF3UkZpejSZiTToh3TmWwjd6v7C8E
> > PXLCFsW1o1RD4pKzYIacUzj5A1VS6TvDBN4+ynQO837jjfHvz6kgAyGryHKoSq7OI71xqrwiX/4W
> > E6a5fnuXGGuPAScuqHa/u88SKGfAOmh1xE5guv5qZcgyhDIB5H5nIQwzyb1trdobmRqUMFT1rT5T
> > sON0C/SB59IEbKITx5ItzheQu7D5erkFYrjhcBV1xNCh0J7uwF5XXF9qVHhlvQyp5AJFF9lSUJB2
> > eTX5ORhCpcGvO/AAhnnlf4DU8C9a7CFVfTfhP+sgs5T7aC1ymojylvBL5TmkAKCna5hN6Ckzr9qH
> > jKYDXAhwJTuMPZkgSFS8OVXkgKnxDS5vG9Ssg0ueb3G7tIEhxt2ehjMgDPK5N/blHnE1t/ZjXe2Q
> > g/TV83LE/MpUKiTQO7JwZ5+tWmT2WWgxK6fG8ckuhlwXhZmVkjWCw+1uxs0C8FrfZFH1ms5MhEyS
> > 6Zgi0803KfOamnH/k6PtEPVB5G7BCWf/b+6Wfo/ZvPSgSYrpcDMJs5j+3KkUjnfpgCuXYXE5TSmE
> > DcrINQHDLYq3hHWklV0n7bFwS3loEWcti/OKQkjeu/3c4E5c/+IWyJFTeLoKEbrNIPtLOYAvsRf+
> > FJHYzqQyEWoqgAejX6K/XWclKrFAePkjKTouj10ppv9WENd+KCnK7JErZp2zqKwJeGZcOlHsFJ9C
> > dUTWFgOU3VzsWiYMnxuPHnvYt3uXr6XlFQHA818kZdcJIMvfUPLRNhrBwR893vTd5aw6/tb4EPeR
> > HacNklguWar6H9w69r8KY2yqk9cepySCDkomVGFqmi5gPH9anFGfEKEUJhKNdjMqF44jx76odAOZ
> > ijoW+F9h6qHVQFGSLhxchqcMWgA+0aBVz9My+PoRzIsXEmH+21W9ucie9zPCw3QWVVPxgAAAAACQ
> > pqAPsaqrpAAB3gWAUAAAeb5korHEZ/sCAAAAAARZWg==
> > EOF
> >
> > I tested that the following packages still compile:
> > - libglib2
> > - gst1-plugins-bad
> > - gst1-plugins-base
> > - gst1-plugins-good
> > - gst1-plugins-ugly
> > - gstreamer1
> > - libdrm
> > - mesa3d
> > ---
> >  package/pkg-meson.mk | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/package/pkg-meson.mk b/package/pkg-meson.mk
> > index e7eea2aa58..349da39369 100644
> > --- a/package/pkg-meson.mk
> > +++ b/package/pkg-meson.mk
> > @@ -84,7 +84,8 @@ define $(2)_CONFIGURE_CMDS
> >           ) \
> >           package/meson/cross-compilation.conf.in \
> >           > $$($$(PKG)_SRCDIR)/build/cross-compilation.conf
> > -     PATH=$$(BR_PATH) $$($$(PKG)_CONF_ENV) $$(MESON) \
> > +     PATH=$$(BR_PATH) PKG_CONFIG=$(HOST_DIR)/bin/pkgconf \
> > +     $$($$(PKG)_CONF_ENV) $$(MESON) \
> >               --prefix=/usr \
> >               --libdir=lib \
> >               --default-library=$(if $(BR2_STATIC_LIBS),static,shared) \
> >
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