Re: [Xen-devel] [PATCH RFC-for-4.12] tools/xen-foreign: Update python scripts to be Py3 compatible

[Juergen Gross <jgross@xxxxxxxx>]

On 04/03/2019 20:00, George Dunlap wrote:
> On 3/4/19 6:31 PM, Andrew Cooper wrote:
>> The issues are:
>>  * dict.has_key() was completely removed in Py3
>>  * dict.keys() is an iterable rather than list in Py3, so .sort() doesn't 
>> work.
>>  * list.sort(cmp=) was deprecated in Py2.4 and removed in Py3.  Replace it
>>    with a key= sort instead.
>>
>> This is all compatible with Py2.4 and later, which is when the sorted()
>> builtin was introduced.  Tested with Py2.7 and Py3.4
> 
> Did you test ./configure with python3?
> 
> Loads of the python-related runes in the configure are also
> python2-only, resulting in (at least for me) the wrong library paths
> being generated, so the following fails:
> 
>     PYTHON=/usr/bin/python3 ./configure
> 
> With the following message:
> 
>   File "<string>", line 1
>     import distutils.sysconfig;     print
> distutils.sysconfig.get_config_var("VERSION")
>                                                   ^
> SyntaxError: invalid syntax
> checking for python3-config... /home/gdunlap/anaconda3/bin/python3-config
> checking Python.h usability... yes
> checking Python.h presence... yes
> checking for Python.h... yes
> checking for PyArg_ParseTuple in -lpython... no
> configure: error: Unable to find a suitable python development library
> configure: error: ./configure failed for tools
> 
> Note the error with the VERSION above; that results in looking for
> `-lpython` rather than `-lpython3.7`, which results in the following
> line being executed:
> 
> configure:7468: checking for PyArg_ParseTuple in -lpython
> configure:7493: gcc -o conftest -g -O2 -g -O2
> -I/persistent/local/home/dunlapg/anaconda3/include/python3.7m
> -I/persistent/local/home/dunlapg/anaconda3/include/python3.7m
> -Wno-unused-result -Wsign-compare -march=nocona -mtune=haswell
> -ftree-vectorize -fPIC -fstack-protector-strong -fno-plt -O3 -pipe
> -fdebug-prefix-map==/usr/local/src/conda/-
> -fdebug-prefix-map==/usr/local/src/conda-prefix -fuse-linker-plugin
> -ffat-lto-objects -flto-partition=none -flto -flto -fuse-linker-plugin
> -ffat-lto-objects -flto-partition=none -g -DNDEBUG -fwrapv -O3 -Wall
> -L/persistent/local/home/dunlapg/anaconda3/lib/python3.7/config-3.7m-x86_64-linux-gnu
> -L/persistent/local/home/dunlapg/anaconda3/lib -lpython3.7m -lpthread
> -ldl  -lutil -lrt -lm  -Xlinker -export-dynamic conftest.c -lpython
> -llzma  -lpython3.7m -lpthread -ldl  -lutil -lrt -lm  -llzma  >&5
> /usr/bin/ld: cannot find -lpython
> collect2: error: ld returned 1 exit status
> 
> The following fixes it for me:
> 
> diff --git a/tools/configure b/tools/configure
> index acc857510e..d7e21db959 100755
> --- a/tools/configure
> +++ b/tools/configure
> @@ -6953,7 +6953,7 @@ if echo "$PYTHON" | grep -q "^/"; then :
>      PYTHON=`basename $PYTHONPATH`
> 
>  elif test -z "$PYTHON"; then :
> -  PYTHON="python"
> +  PYTHON="python2"
>  else
>    as_fn_error $? "PYTHON specified, but is not an absolute path"
> "$LINENO" 5
>  fi
> diff --git a/tools/configure.ac b/tools/configure.ac
> index 1499344ce6..adf70aeb33 100644
> --- a/tools/configure.ac
> +++ b/tools/configure.ac
> @@ -355,7 +355,7 @@ esac
>  AS_IF([echo "$PYTHON" | grep -q "^/"], [
>      PYTHONPATH=$PYTHON
>      PYTHON=`basename $PYTHONPATH`
> -],[test -z "$PYTHON"], [PYTHON="python"],
> +],[test -z "$PYTHON"], [PYTHON="python2"],
>  [AC_MSG_ERROR([PYTHON specified, but is not an absolute path])])
>  AX_PATH_PROG_OR_FAIL([PYTHONPATH], [$PYTHON])
>  AX_CHECK_PYTHON_VERSION([2], [3])
> 
> ..but:
> 1) I'm not sure if we can guarantee that `python2` will exist on all
> systems we support,
> 2) We probably want to support python3 at some point anyway.
> 
> On the other hand, Arch has python -> python3, but (apparently) has
> since 2011 [1]; so there's an argument to be made that this isn't
> something that needs to be solved for 4.12.

Which raises the question whether Andrew's patch should be included
in 4.12. I'm tempted to refuse my Rab as I don't see why we need to
be python3 compliant in the build system while configure isn't.

Thoughts?


Juergen

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