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

[George Dunlap <george.dunlap@xxxxxxxxxx>]

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.

 -George

[1] https://www.python.org/dev/peps/pep-0394/

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