F21 system GCC changed to 4.9.0 prerelease

[Przemek Klosowski]

On 04/11/2014 05:10 AM, Jakub Jelinek wrote:
> On Fri, Apr 11, 2014 at 11:32:53AM +0300, Panu Matilainen wrote:
>> On 04/10/2014 05:38 PM, Richard W.M. Jones wrote:
>>> On Thu, Apr 10, 2014 at 12:23:07PM +0200, Jakub Jelinek wrote:
>>>> To investigate runtime rather than compile time
>>>> issues, please consider using temporarily -fsanitize=undefined and/or
>>>> -fsanitize=address to look for undefined behavior in the packages
>>>> you own.
>>> Which is this in case anyone else was wondering:
>>>
>>>    '-fsanitize=address'
>>>       Enable AddressSanitizer, a fast memory error detector.  Memory
>>>       access instructions will be instrumented to detect out-of-bounds
>>>       and use-after-free bugs.  See
>>>       <http://code.google.com/p/address-sanitizer/> for more details.
>>>       The run-time behavior can be influenced using the 'ASAN_OPTIONS'
>>>       environment variable; see
>>>       <https://code.google.com/p/address-sanitizer/wiki/Flags#Run-time_flags>
>>>       for a list of supported options.
>> Also in case anybody else wonders about gcc failing to recognize
>> these options, you'll need to add BuildRequires for these: libasan
>> for -fsanitize=address and libubsan for -fsanitize=undefined (and
>> similarly for leak and thread sanitizers )
> Yeah.  But, note that the sanitizers are meant primarily for development,
> not for production, and especially -fsanitize=thread and to some extent
> -fsanitize=address aren't completely cheap, so if you do that, please do
> so temporarily and don't forget to disable it again for production.
>
> 	Jakub
FWIW, some liveCD like e.g. the Electronic Lab started failing because

libtool-2.4.2-23.fc21.i686 requires gcc = 4.8.2

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