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Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client

From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client
Date: Mon, 23 Jul 2012 16:23:42 +0100

On Mon, Jul 23, 2012 at 4:16 PM, Laszlo Ersek <address@hidden> wrote:
> On 07/23/12 16:52, Stefan Hajnoczi wrote:
>> On Mon, Jul 23, 2012 at 3:05 PM, Laszlo Ersek <address@hidden> wrote:
>>> The idea is, rather than
>>>     unsigned int id = hub->num_ports++;
>>> it should say
>>>     unsigned int id;
>>>     /* ... */
>>>     id = hub->num_ports++;
>>> ... Hm, yes, I remember it from
>>> <http://www.manpages.info/freebsd/style.9.html>. But again, I'm not sure
>>> how qemu treats this.
>> "Be careful to not obfuscate the code by initializing variables in the
>> declarations.  Use this feature only thoughtfully.  DO NOT use
>> function calls in initializers."
>> This?
>> Do you know the rationale?  It's not clear to me how this "obfuscates" the 
>> code.
> I think the rationale is that (a) people tend to reorganize definitions,
> and the expressions in the initializer lists may depend on the original
> order, (b) even worse with removal of variables, (c) many people have a
> "conceptual divide" between the definition block and the logic below it,
> and the first should set constant defaults at most. (Naturally this
> prevents C99/C++ style mixing of definitions and code as well, at least
> without explicit braces.)
> I'm one of those people, but again I'm not sure if qemu has any
> guideline on this.
>> Messing around with side-effects in a series of variable declarations
>> with intializers could be bug-prone.  But here there is only one
>> initializer so it's not a problem.
>> Regarding QEMU, there's no coding style rule against initializers.
>> Personally I think that's a good thing because it keeps the code
>> concise - people reading it don't have to keep the declaration in
>> their mind until they hit the initializer later on.
> Well I keep the definitions at the top of the block so I can very easily
> return to them visually (and be sure they do nothing else than define
> variables / declare externs), but it's getting philosophical :)
> I have nothing against this initializer as-is, I just wanted to voice
> *if* there's such a guideline in qemu *then* it should be followed :)

Yes, I understand - it's a question of style or flamewar fodder :).  I
double-checked that there is no guideline in ./CODING_STYLE and


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