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

[Juergen Gross <jgross@xxxxxxxx>]

On 05/03/2019 13:19, George Dunlap wrote:
> On 3/5/19 12:04 PM, Wei Liu wrote:
>> On Tue, Mar 05, 2019 at 12:41:53PM +0100, Juergen Gross wrote:
>>> 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?
>>
>> I plan to have a closer look at python 3 compatibility issue today. But
>> the outcome is unlikely to be simple -- most likely there will be a few
>> patches. I don't think they will be suitable for 4.12.
>>
>> We can document the python 2 requirement for 4.12.
> 
> Right, but there are two issues:
> 1. Build system requires python2
> 2. Build system assumes that 'python' == 'python2', and fails in strange
> ways when it's not
> 
> I agree #1 isn't something to rush before the release.  Any opinions on #2?
> 
> Options are:
> 
> A. Simply document that if 'python'  isn't 'python2' (such as on Arch
> Linux, or if you've got anaconda python installed), you need to
> explicitly set PYTHON=/path/to/python2
> 
> B. Hard-code configure to look for python2 if not specified rather than
> python.
> 
> C. Have configure detect when python is python3, and look for python2,
> failing if it's not available.
> 
> Evaluation:
> 
> Option A isn't a great UI, but the situation has been like this for a
> long time, so it's probably not the worst thing ever to wait for the
> next release to fix things.  Also, serves you right for using such a
> broken distro. :-)
> 
> Option B is dead-simple; I just don't know how far back it will be
> compatible.
> 
> Option C is the most robust, but more work (though probably not a huge
> amount).
> 
> Thoughts?

I'm hoping to have 4.12 finished rather soon (maybe one further RC?).

For this reason I'd like to include fixes for regressions only from now
on. This would imply option A.


Juergen

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