[Python-ideas] Update the required C compiler for Windows to a supported version.

[Steve Dower]

Not at my desk, so I can only get you started (didn't want to keep you waiting until Monday). It'll look something like this:

IF %1 eq x86 CALL bin\vcvars32.bat %*
IF %1 eq amd64 CALL bin\vcvars64.bat %*
(similar for x86_amd64)

The file should go at C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcvarsall.bat

If you want to redistribute something that will work for others, it's possible to monkey patch distutils from your setup.py. I can't remember the specifics right now, so I can't help with that until I'm back at work. I think that's the best long term solution for 2.7 packages that want to build on Windows.

Cheers,
Steve

Top-posted from my Windows Phone
________________________________
From: Vernon D. Cole<mailto:vernondcole at gmail.com>
Sent: ‎3/‎1/‎2014 2:24
To: Steve Dower<mailto:Steve.Dower at microsoft.com>
Cc: Stephen J. Turnbull<mailto:stephen at xemacs.org>; python-ideas<mailto:python-ideas at python.org>
Subject: Re: [Python-ideas] Update the required C compiler for Windows to a supported version.

Sorry to resurrect this thread after so long a time, but I am starting to work on a project where I need this again...

Any chance that I can get a copy (or a link to) " the vcvarsall.bat file that distutils expects. (Though it's pretty simple to add one" ?
It's only simple to add one if you know what changes to make.
--
VC



On Wed, Nov 27, 2013 at 7:24 PM, Steve Dower <Steve.Dower at microsoft.com<mailto:Steve.Dower at microsoft.com>> wrote:
Stephen J. Turnbull wrote:
> Vernon D. Cole writes:
>
>> I cannot compile a Python extension module with any Microsoft compiler
>> I can obtain.
>
> Your pain is understood, but it's not simple to address it.

FWIW, I'm working on making the compiler easily obtainable. The VS 2008 link that was posted is unofficial, and could theoretically disappear at any time (I'm not in control of that), but the Windows SDK for Windows 7 and .NET 3.5 SP1 (http://www.microsoft.com/en-us/download/details.aspx?id=3138) should be around for as long as Windows 7 is supported. The correct compiler (VC9) is included in this SDK, but unfortunately does not install the vcvarsall.bat file that distutils expects. (Though it's pretty simple to add one that will switch on %1 and call the correct vcvars(86|64|...).bat.)

The SDK needed for Python 3.3 and 3.4 (VC10) is even worse - there are many files missing. I'm hoping we'll be able to set up some sort of downloadable package/tool that will fix this. While we'd obviously love to move CPython onto our latest compilers, it's simply not possible (for good reason). Python 3.4 is presumably locked to VC10, but hopefully 3.5 will be able to use whichever version is current when that decision is made.

> The basic problem is that the ABI changes.  Therefore it's going to require
> a complete new set of *all* C extensions for Windows, and the duplication
> of download links for all those extensions from quite a few different vendors
> is likely to confuse a lot of users.

Specifically, the CRT changes. The CRT is an interesting mess of data structures that are exposed in header files, which means while you can have multiple CRTs loaded, they cannot touch each other's data structures at all or things will go bad/crash, and there's no nice way to set it up to avoid this (my colleague who currently owns MSVCRT suggested a not-very-nice way to do it, but I don't think it's going to be reliable enough). Python's stable ABI helps, but does not solve this problem.

The file APIs are the worst culprits. The layout of FILE* objects can and do change between CRT versions, and file descriptors are simply indices into an array of these objects that is exposed through macros rather than function calls. As a result, you cannot mix either FILE pointers or file descriptors between CRTs. The only safe option is to build with the matching CRT, and for MSVCRT, this means with the matching compiler. It's unfortunate, and the responsible teams are well aware of the limitation, but it's history at this point, so we have no choice but to work with it.

Cheers,
Steve

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