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[Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE |
Date: |
Wed, 19 Nov 2008 16:50:17 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Anthony Liguori wrote:
> Jan Kiszka wrote:
>> Add TAILQ iterator that allows to safely remove elements while walking
>> the list.
>>
>> Signed-off-by: Jan Kiszka <address@hidden>
>> ---
>>
>> sys-queue.h | 6 ++++++
>> 1 files changed, 6 insertions(+), 0 deletions(-)
>>
>> diff --git a/sys-queue.h b/sys-queue.h
>> index 3d0773e..b92a77f 100644
>> --- a/sys-queue.h
>> +++ b/sys-queue.h
>> @@ -210,6 +210,12 @@ struct
>> { \
>>
>> (var); \
>> (var) = ((var)->field.tqe_next))
>>
>> +#define TAILQ_FOREACH_SAFE(var, head, field,
>> next_var) \
>> + for ((var) =
>> ((head)->tqh_first); \
>> + (var) ? ({ (next_var) = ((var)->field.tqe_next); 1;
>> }) \
>> + :
>> 0; \
>> + (var) = (next_var))
>>
>
> So the Linux implementation of this is:
>
> #define list_for_each_safe(pos, n, head) \
> for (pos = (head)->next, n = pos->next; pos != (head); \
> pos = n, n = pos->next)
This would relate to CIRCLEQ, not TAILQ.
>
> I'd prefer something similar:
>
> #define TAILQ_FOREACH_SAFE(var, head, field, next_var)
> for (var = (head)->tqh_first, next_var = var->field.tqe_next;
> var;
> var = next_var, next_var = var->field.tqe_next)
>
> As it's functionally equivalent and avoids using a GCC-ism ({}).
Won't fly, next_var can become NULL and would be dereferenced without a
prior check. Unless I'm totally blind now, there is no
TAILQ_FOREACH_SAFE without "GCC-ism". But I think I could switch to
CIRCLEQ and add CIRCLEQ_FOREACH_SAFE instead.
Jan
--
Siemens AG, Corporate Technology, CT SE 2 ES-OS
Corporate Competence Center Embedded Linux
- [Qemu-devel] [PATCH 0/2] Use TAILQ for breakpoints, Jan Kiszka, 2008/11/19
- [Qemu-devel] [PATCH 2/2] Use sys-queue.h for break/watchpoint managment, Jan Kiszka, 2008/11/19
- [Qemu-devel] [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Jan Kiszka, 2008/11/19
- Re: [Qemu-devel] [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Anthony Liguori, 2008/11/19
- [Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE,
Jan Kiszka <=
- Re: [Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Anthony Liguori, 2008/11/19
- [Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Jan Kiszka, 2008/11/20
- Re: [Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Jamie Lokier, 2008/11/20
- [Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Jan Kiszka, 2008/11/24
- [Qemu-devel] Re: [PATCH 1/2] Add TAILQ_FOREACH_SAFE, Anthony Liguori, 2008/11/25