Re: Python2 and Python3 checks

[Bob Friesenhahn]

On Thu, 22 Mar 2018, Matěj Týč wrote:

> On 21.3.2018 22:34, Bob Friesenhahn wrote:
> > On Wed, 21 Mar 2018, Matěj Týč wrote:
> >
> > > The question stands like this: Is there a demand on automake side to fix 
> > > this issue - to allow developers addressing multiple Python interpreters 
> > > of different major versions? If so, I think that I can come up with some 
> > > patches to get this working.
> >
> > Is there a purpose to this macro from an Automake (creating Makefiles) 
> > standpoint?  Does Automake offer special Python module building support 
> > which depends on the Python version?
>
> Majority of packages that use Autotools are C/C++ libraries, and they may 
> want to build bindings for Python. As Python2 is the only supported Python 
> e.g. in RHEL7, but it is also possible to obtain Python3, there will be 
> demand for this for years and years to come as for the developer, supporting 
> bindings for multiple Python major versions is a relatively cheap task.

RHEL7 is very conservative.  I have heard that some major 
distributions are now standardizing/defaulting to Python3, although 
they allow installing Python2.

> > The ability to specify a maximum version sounds useful but it is difficult 
> > to foretell the future and a package using the feature might be adding an 
> > artificial limitation which eventually leads to failures because the 
> > requested version range is no longer in use.
> Again, the main target group is library developers providing bindings. 
> Projects with lots of Python code will not use Autotools at all. Therefore, 
> it is not so much about capping the version, but it is about distinguishing 
> that there may be more than one major Python version that needs to be dealt 
> with in the build and install process.

You make a good point that it is possible that a package will want to 
discover multiple Python versions and build extensions for each 
version found.  Is this something you would like to support?

The question to be answered is if updating Automake's macro is the 
best course (requiring updating Automake to the version providing the 
macro in order to use it) or if a macro in something like the Autoconf 
macro archive is the safer approach.

A stable distribution may not want to update the Automake version for 
a few years but they might also want to re-autotool packages while 
building them.  In this case, a cached .m4 file with the macro will 
still work while depending on a macro from a latest Automake won't 
work because the distribution has chosen not to be up to date.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/