Re: [Xen-devel] [PATCH v2] autoconf: fix python-dev detection on old python versions

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-03-30 at 08:35 +0100, Roger Pau Monne wrote:
> Replaced the use of python-config (that is only present in Python >= 2.5.x)
> with the distutils python module.
> 
> Please run ./autogen.sh after applying the patch.
> 
> Again, this has only been tested on OS X Python 2.7.
> 
> Changes since v1:
> 
>  * Added Python LDFLAGS to library test.
> 
> Signed-off-by: Roger Pau Monne <roger.pau@xxxxxxxxxxxxx>
> Cc: Zhang, Yang Z <yang.z.zhang@xxxxxxxxx>
> Cc: KUWAMURA Shin'ya <kuwa@xxxxxxxxxxxxxx>
> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
>  tools/m4/python_devel.m4 |   36 +++++++++++++++++-------------------
>  1 files changed, 17 insertions(+), 19 deletions(-)
> 
> diff --git a/tools/m4/python_devel.m4 b/tools/m4/python_devel.m4
> index 3bcca7b..dada92a 100644
> --- a/tools/m4/python_devel.m4
> +++ b/tools/m4/python_devel.m4
> @@ -1,27 +1,25 @@
>  AC_DEFUN([AX_CHECK_PYTHON_DEVEL], [
> +ac_python_version=`$PYTHON -c 'import distutils.sysconfig; \
> +    print distutils.sysconfig.get_config_var("VERSION")'`
>  ac_previous_cppflags=$CPPFLAGS
> -CPPFLAGS="$CFLAGS `$PYTHON-config --includes`"
> +CPPFLAGS="$CFLAGS `$PYTHON -c 'import distutils.sysconfig; \
> +    print "-I" + distutils.sysconfig.get_config_var("INCLUDEPY")'`"
> +CPPFLAGS="$CPPFLAGS `$PYTHON -c 'import distutils.sysconfig; \
> +    print distutils.sysconfig.get_config_var("CFLAGS")'`"

This mixes up CPPFLAGS and CFLAGS in what looks like a very strange way
to me, is it right?

[...]

> +LDFLAGS="$LDFLAGS `$PYTHON -c 'import distutils.sysconfig; \
> +    print distutils.sysconfig.get_config_var("LIBS")'`"
> +LDFLAGS="$LDFLAGS `$PYTHON -c 'import distutils.sysconfig; \
> +    print "-L" + distutils.sysconfig.get_python_lib(plat_specific=1,\
> +    standard_lib=1) + "/config"'`"
> +LDFLAGS="$LDFLAGS `$PYTHON -c 'import distutils.sysconfig; \
> +    print distutils.sysconfig.get_config_var("LINKFORSHARED")'`"

Elsewhere in the Xen build system we would call these LDLIBS_<blah>
and/or SHLIBS_<blah> (see tools/Rules.mk for examples). I think in the
case of libpython, which is not built in tree you would only want to use
SHLIBS_PYTHON.

On a similar note do we really want to add the python stuff to the
global CFLAGS and LDFLABS etc? Wouldn't it be better to have
CFLAGS_PYTHON etc and to use them explicitly in tools/python/Makefile
rather than using them for all compilations?

Although that might require other build system changes which could be
done later in the interests of fixing getting a fix for people using
python 2.3/2.4 into the tree.

> +LDFLAGS="$LDFLAGS `$PYTHON -c 'import distutils.sysconfig; \
> +    print distutils.sysconfig.get_config_var("LDFLAGS")'`"
> +
>  AC_CHECK_HEADER([Python.h], [],
>      [AC_MSG_ERROR([Unable to find Python development headers])],)
> -AC_CHECK_LIB($python_lib, PyArg_ParseTuple, [],
> +AC_CHECK_LIB(python$ac_python_version, PyArg_ParseTuple, [],
>      [AC_MSG_ERROR([Unable to find a suitable python development library])])
>  CPPFLAGS=$ac_previous_cppflags
>  LDLFAGS=$ac_previous_ldflags



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