[Buildroot] [PATCH v2 1/1] host-libxml2: Prefer python2 when python3 is also installed

[Samuel Martin]

Hi Bernd, Thomas, all,

On Sat, Apr 12, 2014 at 4:53 PM, Bernd Kuhls <bernd.kuhls at t-online.de> wrote:
> Fixes mesa3d build errors:
> http://autobuild.buildroot.net/results/d10/d105a0b3ca11fad34f9a2dae0dae9bd041d918a6/
> http://autobuild.buildroot.net/results/d71/d7121443715024d15a66ff1abf1261803c10cd35/
> http://autobuild.buildroot.net/results/ce6/ce64164d76972f82acab277afc9c95a876c6433e/
>
> checking for python2... python2
> checking python2 module: libxml2... no
> configure: error: failed to find required module libxml2
> make: *** [/home/test/test/1/output/build/mesa3d-10.0.4/.stamp_configured] Error 1
>
> mesa3d needs python2 bindings installed by libxml2. To enforce their build
> option BR2_PACKAGE_HOST_LIBXML2_PYTHON is used exclusively by mesa3d so this
> patch does not affect other packages.
>
> Without this patch host-libxml2 installs the python bindings in
> $(HOST_DIR)/usr/lib/$(PYTHON3_VERSION_MAJOR) using this defconfig:
>
> BR2_PACKAGE_MESA3D=y
> BR2_PACKAGE_PYTHON3=y
>
> because $(HOST_DIR)/usr/bin/python points to $(HOST_DIR)/usr/bin/python3:
>
> Quote from host-libxml2 configure log:
> Found python in /home/fli4l/br2/buildroot/output/host/usr/bin/python
> Found Python version 3.4
>
> HOST_$(PACKAGE)_NEEDS_HOST_PYTHON does not work here because libxml2 does
> not use the python-package infrastructure.
>
> libxml2-python2.patch extends the python detection code in host-libxml2 to
> first look for python2, to keep the patch small I did not update the indentions:
>
> Found python2 in /home/fli4l/br2/buildroot/output/host/usr/bin/python2
> Found Python version 2.7
>
> Signed-off-by: Bernd Kuhls <bernd.kuhls at t-online.de>
> ---
> v2: Add more autobuilder URLs, add s-o-b to patch file
>
>  package/libxml2/libxml2-python2.patch |   27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>  create mode 100644 package/libxml2/libxml2-python2.patch
>
> diff --git a/package/libxml2/libxml2-python2.patch b/package/libxml2/libxml2-python2.patch
> new file mode 100644
> index 0000000..19195a6
> --- /dev/null
> +++ b/package/libxml2/libxml2-python2.patch
> @@ -0,0 +1,27 @@
> +Prefer python2 binary in case python points to python3
> +
> +Signed-off-by: Bernd Kuhls <bernd.kuhls at t-online.de>
> +
> +diff -uNr libxml2-2.9.1.org/configure.in libxml2-2.9.1/configure.in
> +--- libxml2-2.9.1.org/configure.in     2013-04-19 09:25:20.000000000 +0200
> ++++ libxml2-2.9.1/configure.in 2014-04-12 14:16:26.579361068 +0200
> +@@ -748,6 +748,11 @@
> + PYTHON_TESTS=
> + pythondir=
> + if test "$with_python" != "no" ; then
> ++    if test -x "$with_python/bin/python2"
> ++    then
> ++        echo Found python2 in $with_python/bin/python2
> ++        PYTHON="$with_python/bin/python2"
> ++    else
> +     if test -x "$with_python/bin/python"
> +     then
> +         echo Found python in $with_python/bin/python
> +@@ -773,6 +778,7 @@
> +           fi
> +       fi
> +     fi
> ++    fi
> +     if test "$PYTHON" != ""
> +     then
> +         PYTHON_VERSION=`$PYTHON -c "from distutils import sysconfig; print(sysconfig.get_python_version())"`
> --
> 1.7.10.4

At first, I was a bit dubious because this patch make the host libxml2
python module only built for python2. I was a bit worried if some
other package would need the libxml2 python module for python3 when
BR2_PACKAGE_PYTHON3=y.

If this case pops up, we will have to work on offering host python
modules for both python2 and python3 when both host-python and
host-python3 are built. But, it's not yet the case! :-)


>From quick tests, it appears that among the packages depending on
host-libxml2, only mesa3d uses the host libxml2 python module (and
requires it built for python2), others depend on it for the xmllint
program (@Bernd, this point was not obvious in the commit log IMHO).

Also, I've successfully run a build with many target packages
depending on libxml2 (all except classpath, libglade, libsexy, webkit
and xbmc).


Since the host libxml2 python module seems only used by mesa3d so far,
I have no objection to get this patch merged. However, it could be
worthwhile to expand the libmxl2 patch description and the commit log
for the future, in case we trigger other failures because of the host
libxml2 python module for python2.

So:
Tested-by: Samuel Martin <s.martin49 at gmail.com>


Regards,

-- 
Samuel