[Python-Dev] Backporting the 3.5+ Windows build project files to 2.7

[M.-A. Lemburg]

On 25.06.2015 17:12, Zachary Ware wrote:
> On Thu, Jun 25, 2015 at 8:54 AM, M.-A. Lemburg <mal at egenix.com> wrote:
>> On 22.06.2015 19:03, Zachary Ware wrote:
>>> Using the backported project files to build 2.7 would require two
>>> versions of Visual Studio to be installed; VS2010 (or newer) would be
>>> required in addition to VS2008.  All Windows core developers should
>>> already have VS2010 for Python 3.4 (and/or VS2015 for 3.5) and I
>>> expect that anyone else who cares enough to still have VS2008 probably
>>> has (or can easily get) one of the free editions of VS 2010 or newer,
>>> so I don't consider this to be a major issue.
>>
>> To understand this correctly:
>>
>> In order to build Python 2.7.11 (or a later version), we'd
>> now need VS 2008 *and* VS 2010 installed ?
> 
> Using the backported project files, yes, two versions of VS would be
> required.  However, the second version doesn't have to be VS 2010, it
> could be 2010, 2012, 2013, 2015, or any from the future (until
> Microsoft changes the format of the project files again).
> 
>> This doesn't sound like it would make things easier for
>> people who need to build their own Python on Windows, e.g.
>> because they are freezing their apps for distribution, or
>> using their own internal special builds.
>>
>> For VS 2008 we now have a long-term solution thanks to MS.
>> The same is not true for VS 2010 (download links are not official
>> anymore), so we'd complicate things again by requiring the
>> mixed compiler setup.
> 
> For anyone building 2.7 and any other (current) version of Python on
> the same machine, all the necessary pieces are already in place.
> 
> The main motivation for backporting is to make it easier to build
> Python with ICC.  Pre-backport, Intel gave me a list of 9 steps they
> were doing to build 2.7.10 with ICC.  Post-backport, it's just
> `PCbuild\build.bat -e [-p x64] [-d] "/p:PlatformToolset=Intel C++
> Compiler XE 15.0" "/p:BasePlatformToolset=v90"` (the bracketed options
> being optional, for 64-bit and debug builds, respectively).

Sounds good.

BTW: I remember there was some discussion a while ago to
get ICC licenses to core devs. Has there been any progress
on this ?

> There are some benefits for MSVC builds too, though: it's easier to do
> a parallel build, and OpenSSL and Tcl/Tk/Tix are built by the project
> files, so the whole build can be done much quicker.  The new project
> files for Tcl and Tk also take care of copying their DLLs into PCbuild
> so that _tkinter can find them without having to mess around with
> PATH.  My patch also fixes a couple of long-standing bugs with finding
> the right libraries for 64-bit Tcl/Tk and the test suite undoing the
> work of FixTk.py after any test that imports Tkinter, both of which
> were exacerbated by the rest of the patch.
> 
>> If you keep the old VS 2008 build files around, I'd be
>> fine with having an optional upgrade path to newer
>> compilers :-)
> 
> The old files are moved to PC/VS9.0, and they work as expected as far
> as I've tested them. 

So it's still possible to build with "just" VS 2008 installed
or will the VS 2010 (or later) be required for those old
files as well ?

> Btw, the upgrade path to newer compilers is just
> a side-effect which I'm kind of torn about.  On one hand, making it
> easier to build 2.7 with the "wrong" compiler is bound to lead to
> issues somewhere somehow.  On the other hand, people are already doing
> so anyway, with their own upgraded project files.

I guess will have the discussion about switching compilers
for Python 2.7 again at some point. People writing extensions
will sooner or later want to use features from more recent
compilers for Python 2.7 as well :-)

>> It's rather unlikely that the project files will change much
>> in coming years, so there shouldn't be much maintenance
>> effort.
> 
> Hopefully not :) 

-- 
Marc-Andre Lemburg
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