Re: [PATCH 01/10] lib/mbalign: fix unsigned integer overflow [AddressSanitizer]

["Pádraig Brady" <P@draigBrady.com>]

On 04/12/14 20:14, Sami Kerola wrote:
> On 3 December 2014 at 23:53, Pádraig Brady <P@draigbrady.com> wrote:
>> On 30/11/14 13:57, Sami Kerola wrote:
>>> This error was reported 155 times.
>>>
>>> lib/mbsalign.c:322:18: runtime error: unsigned integer overflow: 0 - 1
>>> cannot be represented in type 'size_t' (aka 'unsigned long')
>>
>> What compiler and version are you using for this?
>> I don't get the error with gcc 4.9.2 with -fsanitize=undefined
>> Note the error is incorrect I think as the variable is not read
>> after the overflow.
> 
> Hi Pádraig,
> 
> Sorry it took ages to reply to a trivial question.
> 
> $ clang --version
> clang version 3.5.0 (tags/RELEASE_350/final)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
> 
> I have not done sanitation runs with gcc.
> 
> The system is archlinux with testing repos enabled with daily updates,
> that should mean a lot of libraries and such are fairly recent.

Thanks for the info.
BTW I don't see it with clang 3.4.2.
This seems like a too problematic warning TBH,
as unsigned overflow is defined,
the overflow value is not used in this case,
this seems like a very common idiom.

thanks,
Pádraig.