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Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines |
Date: |
Wed, 12 Sep 2012 06:59:55 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 |
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 address@hidden +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- Re: [Qemu-devel] [PATCH V2 1/6] libqblock API design, (continued)
[Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Wenchao Xia, 2012/09/10
Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Blue Swirl, 2012/09/11
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Eric Blake, 2012/09/11
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Wenchao Xia, 2012/09/11
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines,
Eric Blake <=
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Wenchao Xia, 2012/09/12
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Eric Blake, 2012/09/12
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Eric Blake, 2012/09/12
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Blue Swirl, 2012/09/14
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Wenchao Xia, 2012/09/16
- Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Blue Swirl, 2012/09/17
Re: [Qemu-devel] [PATCH V2 2/6] libqblock type and structure defines, Blue Swirl, 2012/09/14