Re: [PATCH v4 15/15] daemon: opt-out on features that require posix

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 18, 2010, 19:26 UTC
Message-ID: <7vaamb480p.fsf@alter.siamese.dyndns.org>
In-Reply-To: <AANLkTim0KeW3eDHAsxrxMCvBUD_15R3VSrHSzOFq38A1@mail.gmail.com>

Erik Faye-Lund <kusmabite@gmail.com> writes:

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> (I'm going a little off-topic here, I hope that's OK)
> I'm not too happy with some of the pretend-really-hard-to-be-posix-magic
> around in the Windows-port. In fact, I have some patches to reduce
> posixness in some areas, while getting rid of some code in
> mingw.c. Would such patches be welcome, or is pretend-to-be-posix the
> governing portability approach? In some cases, this comes at the expense
> of some performance (and quite a bit of added cludge), which is a bit
> contradictory to the Git design IMO.

If the part of the codepath you need to make conditional can be better helped by abstraction that is higher-level than POSIX, that would be a very acceptable approach. The "struct credential" idea Jonathan gave you is an example of such. The goal is not to force POSIX on Windows or make POSIX emulation on Windows more complete---that is not git's job. Just that in most of the case the level of abstraction POSIX gives has been adequate for our codebase.

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>> This is especially
>> true if you are making the "drop-privileges" part a helper function, no?
>
> I don't follow this part. What exactly becomes more true by having a
> drop-privileges function?

By using a bit higher level abstraction than POSIX primitives give you (e.g. initgroups(), setgid(), etc.) that does not have to depend on particular POSIX implementation details (e.g. "struct passwd", gid_t, etc.), you can make the main codepath cleaner and free of ifdefs.