Re: [Qemu-devel] [PATCH 1/4] configure: keep track of Python version

[Cleber Rosa <crosa@redhat.com>]

On 11/9/18 10:49 AM, Eduardo Habkost wrote:
> On Fri, Nov 09, 2018 at 10:07:07AM -0500, Cleber Rosa wrote:
>> Some functionality is dependent on the Python version
>> detected/configured on configure.  While it's possible to run the
>> Python version later and check for the version, doing it once is
>> preferable.  Also, it's a relevant information to keep in build logs,
>> as the overall behavior of the build can be affected by it.
>>
>> Signed-off-by: Cleber Rosa <crosa@redhat.com>
>> ---
>>  configure | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure b/configure
>> index 74e313a810..67fff0290d 100755
>> --- a/configure
>> +++ b/configure
>> @@ -1740,6 +1740,9 @@ if ! $python -c 'import sys; sys.exit(sys.version_info < (2,7))'; then
>>        "Use --python=/path/to/python to specify a supported Python."
>>  fi
>>  
>> +# Preserve python version since some functionality is dependent on it
>> +python_version=$($python -V 2>&1 | sed -e 's/Python\ //')
> 
> What about:
>   $($python -c 'import sys;print(sys.version)')
> ?
> 
> It is very verbose, but I think that's a good thing.
> 

Well, something like:

'3.7.1 (default, Oct 23 2018, 18:19:07) \n[GCC 8.2.1 20180801 (Red Hat
8.2.1-2)]'

Doesn't qualify as simply the Python *version*.  The documentation[1]
puts it clearly: "A string containing the version number of the Python
interpreter plus additional information on the build number and compiler
used. This string is displayed when the interactive interpreter is started."

I can't see how the compiler used on the Python build, or the build
date, can be significant to someone debugging the type of Python code
that will be on QEMU.

>> +
>>  # Suppress writing compiled files
>>  python="$python -B"
>>  
>> @@ -5918,7 +5921,7 @@ echo "LDFLAGS           $LDFLAGS"
>>  echo "QEMU_LDFLAGS      $QEMU_LDFLAGS"
>>  echo "make              $make"
>>  echo "install           $install"
>> -echo "python            $python"
>> +echo "python            $python ($python_version)"
>>  if test "$slirp" = "yes" ; then
>>      echo "smbd              $smbd"
>>  fi
>> @@ -6823,6 +6826,7 @@ echo "INSTALL_DATA=$install -c -m 0644" >> $config_host_mak
>>  echo "INSTALL_PROG=$install -c -m 0755" >> $config_host_mak
>>  echo "INSTALL_LIB=$install -c -m 0644" >> $config_host_mak
>>  echo "PYTHON=$python" >> $config_host_mak
>> +echo "PYTHON_VERSION=$python_version" >> $config_host_mak
> 
> The output of "python -V" and "sys.version" seems to be meant for
> humans, not software.  If we really want something to be used in
> conditional makefile rules, I'd prefer to use sys.version_info.
> e.g.:
> 

"Python -V" is quite different from "sys.version".  Indeed it includes
the "Python " prefix, but that's all, everything else is the version number.

>   python_major_version="$($python -c 'import sys;print(sys.version_info[0])')"
>   echo "PYTHON_MAJOR_VERSION=$python_major_version"
> 
> 

No, I'm actually interested in the other version components, not just
the major version.  As I tried to explain in another thread, differences
from Python 3.0 to 3.4 are many, and from 3.4 to 3.6 and so on.

Then, we can either introduce "PYTHON_MAJOR_VERSION",
"PYTHON_MINOR_VERSION", "PYTHON_RELEASE" of sorts, or just have a single
dot separated version string.

- Cleber

[1] - https://docs.python.org/3/library/sys.html#sys.version

>>  echo "CC=$cc" >> $config_host_mak
>>  if $iasl -h > /dev/null 2>&1; then
>>    echo "IASL=$iasl" >> $config_host_mak
>> -- 
>> 2.19.1
>>
>