From: Eric Blake <eblake@redhat.com>
To: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Cc: kwolf@redhat.com, aliguori@us.ibm.com, stefanha@gmail.com,
qemu-devel@nongnu.org, Blue Swirl <blauwirbel@gmail.com>,
pbonzini@redhat.com
Subject: Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines
Date: Wed, 12 Sep 2012 06:59:55 -0600 [thread overview]
Message-ID: <5050874B.4050505@redhat.com> (raw)
In-Reply-To: <504FFC05.5070601@linux.vnet.ibm.com>
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On 09/11/2012 09:05 PM, Wenchao Xia wrote:
>> Seriously? We require a C99-compliant compiler, which is required to
>> treat the more compact version identically (all undefined names evaluate
>> to 0 in the preprocessor), and HACKING doesn't mandate that we spell out
>> a defined-ness check first. Okay, so configure adds -Wundef to the set
>> of CFLAGS, but I fail to see why we want -Wundef (that's an
>> anachronistic warning, only there to help you if you are writing code
>> portable to K&R).
>>
> So if the preprocessor replaced __GNUC__ to 0, is there difference
> between these two kinds of macoros?
> #if __GNUC__ >= 4
> #if defined(__GNUC__) && __GNUC__ >=4
The only difference is whether -Wundef will warn, and I'm trying to
argue that qemu's current use of -Wundef is pointless, as that warning
exists solely for K&R compatibility, not for modern standard-compliant
code correctness.
--
Eric Blake eblake@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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next prev parent reply other threads:[~2012-09-12 13:00 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-10 8:26 [Qemu-devel] [PATCH V2 0/6] libqblock, qemu block layer library Wenchao Xia
2012-09-10 8:26 ` [Qemu-devel] [PATCH V2 1/6] libqblock API design Wenchao Xia
2012-09-10 21:07 ` Eric Blake
2012-09-11 3:16 ` Wenchao Xia
2012-09-14 2:03 ` Wenchao Xia
2012-09-11 20:28 ` Blue Swirl
2012-09-12 2:54 ` Wenchao Xia
2012-09-12 8:19 ` Kevin Wolf
2012-09-12 9:21 ` Wenchao Xia
2012-09-14 19:08 ` Blue Swirl
2012-09-10 8:26 ` [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines Wenchao Xia
2012-09-10 21:27 ` Eric Blake
2012-09-11 3:26 ` Wenchao Xia
2012-09-11 4:12 ` Eric Blake
2012-09-11 20:31 ` Blue Swirl
2012-09-11 22:52 ` Eric Blake
2012-09-12 3:05 ` Wenchao Xia
2012-09-12 12:59 ` Eric Blake [this message]
2012-09-13 3:24 ` Wenchao Xia
2012-09-13 3:33 ` Eric Blake
2012-09-13 3:49 ` Eric Blake
2012-09-14 18:11 ` Blue Swirl
2012-09-17 2:23 ` Wenchao Xia
2012-09-17 19:08 ` Blue Swirl
2012-09-14 18:02 ` Blue Swirl
2012-09-10 8:26 ` [Qemu-devel] [PATCH V2 3/6] libqblock error handling Wenchao Xia
2012-09-10 21:33 ` Eric Blake
2012-09-11 4:36 ` Wenchao Xia
2012-09-11 20:32 ` Blue Swirl
2012-09-12 2:58 ` Wenchao Xia
2012-09-14 17:09 ` Blue Swirl
2012-09-10 8:26 ` [Qemu-devel] [PATCH V2 4/6] libqblock export some qemu block function Wenchao Xia
2012-09-10 8:26 ` [Qemu-devel] [PATCH V2 5/6] libqblock building system Wenchao Xia
2012-09-10 8:26 ` [Qemu-devel] [PATCH V2 6/6] libqblock test example Wenchao Xia
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