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Re: [Qemu-devel] [PATCH v3 1/8] CODING_STYLE: Section about conditional
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v3 1/8] CODING_STYLE: Section about conditional statement |
Date: |
Fri, 01 Aug 2014 10:01:28 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 |
On 08/01/2014 01:46 AM, address@hidden wrote:
> From: Gonglei <address@hidden>
>
> Yoda conditions lack readability, and QEMU has a
> strict compiler configuration for checking a common
> mistake like "if (dev = NULL)". Make it a written rule.
>
> Signed-off-by: Gonglei <address@hidden>
> ---
> CODING_STYLE | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/CODING_STYLE b/CODING_STYLE
> index 4280945..b08bfb4 100644
> --- a/CODING_STYLE
> +++ b/CODING_STYLE
> @@ -91,3 +91,17 @@ Mixed declarations (interleaving statements and
> declarations within blocks)
> are not allowed; declarations should be at the beginning of blocks. In other
> words, the code should not generate warnings if using GCC's
> -Wdeclaration-after-statement option.
> +
> +6. Conditional statements
> +
> +When comparing a variable for (in)equality with a constant, list the
> +constant on the right, as in:
> +
> +if (a == 0) {
> + /* Reads like: "If a is equal to 0" */
I actually tend to read it as 'if a equals 0'.
> + do_something();
> +}
> +
> +Rationale: Yoda conditions (as in 'if (0 == a)') are awkward to read.
I know this is my suggested text, but now that I'm re-reading it, I'd
recommend s/0/1/ in all three places, since comparison to 0 is one of
those special cases where '!a' is faster to write than 'a == 0'.
> +Besides, good compilers already warn users when '==' is mis-typed as '=',
> +even when the constant is on the right.
With those changes,
Reviewed-by: Eric Blake <address@hidden>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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[Qemu-devel] [PATCH v3 3/8] audio: don't use 'Yoda conditions', arei.gonglei, 2014/08/01
[Qemu-devel] [PATCH v3 6/8] spice: don't use 'Yoda conditions', arei.gonglei, 2014/08/01
[Qemu-devel] [PATCH v3 7/8] vl: don't use 'Yoda conditions', arei.gonglei, 2014/08/01
[Qemu-devel] [PATCH v3 2/8] usb: don't use 'Yoda conditions', arei.gonglei, 2014/08/01
[Qemu-devel] [PATCH v3 4/8] isa-bus: don't use 'Yoda conditions', arei.gonglei, 2014/08/01
Re: [Qemu-devel] [PATCH v3 for-2.2 0/8] don't use Yoda conditions, Michael S. Tsirkin, 2014/08/05