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Re: [Qemu-trivial] [Qemu-devel] [PATCH] migration: Replace strncpy() by

From: David Hildenbrand
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] migration: Replace strncpy() by g_strlcpy()
Date: Mon, 20 Aug 2018 21:59:04 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 20.08.2018 21:48, Eric Blake wrote:
> On 08/20/2018 12:16 PM, Thomas Huth wrote:
>>> Maybe really set it to zero (memset) before using the g_strlcpy? I am
>>> not a fan of disabling warnings, but if you think this is
>>> easier/cleaner, let's go for that.
> I'm not a fan of strlcpy in general (by the time you've properly set it 
> up to detect/report/avoid truncation errors, you've added more 
> boilerplate code than you would have by just doing memcpy() yourself).
>> FWIW, that new warning from GCC is IMHO just annoying. I had the same
>> problem in the SLOF sources, too:
>> https://github.com/aik/SLOF/commit/d8a9354c2a35136
>> The code with strncpy was perfectly valid before, but to get rid of the
>> warning, I replaced it with a more cumbersome memcpy instead (and mad
>> sure that the memory is already cleared earlier in that function). Now
>> seeing that the problem with strncpy pops up here, too, I think it would
>> maybe be better to shut up the warning of GCC, since it's clearly GCC
>> who's wrong here.
> gcc is not necessarily wrong, as it CAN catch real erroneous uses of 
> strncpy().  It's just that 99% of the time, strncpy() is the WRONG 
> function to use, and so the remaining few cases where it actually does 
> what you want are so rare that you have to consult the manual anyways. 
> If nothing else, the gcc warning is making people avoid strncpy() even 
> where it is safe (which is not a bad thing, in my opinion, because the 
> contract of strncpy() is so counter-intuitive).

I am wondering if we should simply add a helper for these special cases
that zeroes the buffer and uses g_strlcpy(), instead of
ignoring/disabling the warning.



David / dhildenb

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