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Re: Compiler Warning vasnprintf.c (L5107: comparison between signed and

From: Eric Blake
Subject: Re: Compiler Warning vasnprintf.c (L5107: comparison between signed and unsigned int)
Date: Thu, 11 Sep 2014 14:52:32 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0

On 09/11/2014 02:20 PM, Paul Eggert wrote:
> On 09/11/2014 01:05 PM, Дилян Палаузов wrote:
>> vasnprintf.c: In function ‘vasnprintf’:
>> vasnprintf.c:5107:35: warning: comparison between signed and unsigned
>> integer expressions [-Wsign-compare]
>>                          if (count < maxlen
>>                                    ^
>> count is int (signed) and maxlen is size_t (<=> unsigned) (lines 4935
>> and 4936).
> Sure, but 'count' is nonnegative, so the comparison is numerically
> correct and there is no bug here.
> As a general rule gnulib doesn't worry about pacifying gcc
> -Wsign-compare, which issues too many false alarms like this.

While we don't mind easy-to-maintain patches that silence rare warnings,
we are reluctant to dirty up the code base to silence warnings such as
-Wsign-compare that have a very HIGH signal-to-noise ratio.  That's why
many gnulib clients, such as coreutils, have explicitly taken to
compiling with two sets of warning flags, a looser set for gnulib code,
and a stricter set for the policies that are enforced on the
package-local code.  I'd suggest that you look into that approach for
your project rather than hoping that gnulib will make vasnprintf.c
compile warning-free for all the various warning combinations out there.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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