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Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client
From: |
Blue Swirl |
Subject: |
Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client |
Date: |
Mon, 23 Jul 2012 19:01:17 +0000 |
On Mon, Jul 23, 2012 at 4:33 PM, Andreas Färber <address@hidden> wrote:
> Am 23.07.2012 17:23, schrieb Stefan Hajnoczi:
>> 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++;
>>>>
>>>> "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
>> ./HACKING.
>
> Hm, I'm not so much into those documents [cc'ing Blue], but we used to
> be stricter about ANSI C some years back (which iirc forbids
> non-constant expressions in initializers?). FWIW we have since switched
> to C99 struct initializers and use QOM cast macros (that translate to a
> function call) in initializers. -ansi -pedantic is unlikely to get far.
For example in block/vvfat.c, various initializers and nonstandard
stuff like variable length arrays have been used since day one. It's
not the finest example of code in QEMU though.
>
> Cheers,
> Andreas
>
> --
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
>
>
- Re: [Qemu-devel] [PATCH 04/16] hub: Check that hubs are configured correctly, (continued)
- [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Stefan Hajnoczi, 2012/07/20
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Laszlo Ersek, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Stefan Hajnoczi, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Laszlo Ersek, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Stefan Hajnoczi, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Laszlo Ersek, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Stefan Hajnoczi, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Andreas Färber, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client, Markus Armbruster, 2012/07/23
- Re: [Qemu-devel] [PATCH 01/16] net: Add a hub net client,
Blue Swirl <=
[Qemu-devel] [PATCH 15/16] net: determine if packets can be sent before net queue deliver packets, Stefan Hajnoczi, 2012/07/20
[Qemu-devel] [PATCH 05/16] net: Drop vlan argument to qemu_new_net_client(), Stefan Hajnoczi, 2012/07/20
[Qemu-devel] [PATCH 03/16] net: Look up 'vlan' net clients using hubs, Stefan Hajnoczi, 2012/07/20
[Qemu-devel] [PATCH 10/16] net: Rename VLANClientState to NetClientState, Stefan Hajnoczi, 2012/07/20