[Python-Dev] 3.5 release schedule PEP

Steve Dower Steve.Dower at microsoft.com
Wed Sep 24 18:52:46 CEST 2014

M.-A. Lemburg wrote:
> I'd rather be conservative here and wait for another Python release before
> switching VC versions. There are a few important questions that need answers
> before we can consider a new VC version:
> * Will there be free versions available ?
> * Will those free editions include the 64-bit compilers ?
> * Will those free editions include the optimizing compilers ?
> * Is there a roadmap for how long these free versions will remain
> officially available ?
> * Are there issues compiling 3rd party libraries with it ?
> E.g. the numeric and science stacks, the web stacks,
> the deployment stacks, etc.
> * What license terms will the new version have ?
> E.g. GPL compatibility issues, weird exceptions,
> * What will the pricing structure look like ?
> While core devs will get free MSDN licenses, most other 3rd party
> providers will have to buy licenses for the compiler, unless
> they can use the free versions.
> An alternative would be targeting VC13 instead of VC14, in case it has good
> answers for the above questions. It's been around for a year now, so there
> should be more experience available with this version.

(Nit - it's actually VC12 a.k.a. "Visual Studio 2013" - VC13 was skipped. This is what happens when you have separate engineering and marketing teams :) )

I don't have good answers to all of these yet, but none of them are going to be any worse than for VC12. I've forwarded these questions to the people on the VC team who do get to choose the answers, and while I'm not expecting to hear specifics back from them, they are at least aware of the concerns and how important their product is to our community.

There will be free versions available, but I don't know what format they'll be in. Those free editions should include identical compilers to the paid ones - the cases where that hasn't been true have been bugs or due to assumptions that were proven to be incorrect.

The main improvement in this version is that all versions from VC14 should be binary compatible, and so there will always be a free compiler, but it may be VC15/16/etc. and not VC14.

There are certainly issues with 3rd party libraries, largely because all projects have a tendency to take dependencies on compiler/library internals. OpenSSL, for example, redefines the stdout/in/err macros based on the VC version, but the new definitions are no longer valid with VC14, and so they are fixing that. Python itself has a few issues that I have already fixed in my branch. There will certainly be other issues, but an advantage of starting early is that bugs in the compiler itself can be fixed in the compiler.

The license should not change significantly from previous versions. GPL incompatibilities are because the GPL wants to be incompatible with licenses based on different ideologies - AFAIK there's never been anything in the VC licenses preventing whatever redistribution license you like.

Part of my improvements to /PCBuild will help avoid the need for Visual Studio entirely, but the free versions should always be sufficient for building and debugging. I have no insight or control over the pricing structure.


> --
> Marc-Andre Lemburg
> eGenix.com

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