GCC 5 for 14.10 (wily) on July 31

[David Henningsson]

On 2015-07-23 15:42, Dimitri John Ledkov wrote:
> On 23 July 2015 at 12:39, David Henningsson
> <david.henningsson at canonical.com> wrote:
>>
>>
>> On 2015-07-20 23:44, Matthias Klose wrote:
>>>
>>> Hi,
>>>
>>> We are currently preparing the switch to GCC 5 as the default compiler for
>>> 14.10
>>> (wily).  Unlike earlier updates to newer compiler versions, which only
>>> required
>>> updating packages to newer language standards, this time we have a partial
>>> ABI
>>> transition in the standard C++ library (libstdc++6).
>>
>>
>> That sounds scary, but maybe it's not as scary as it sounds. Will this also
>> affect everyone outside the main repo distributing binary packages (e g,
>> Google Hangout)?
>>
>> How will the versioning of libstdc++ look like, in order to make sure no
>> packages are linking against a libstdc++ they are incompatible with?
>
> So libstdc++ 98 abi is not broken, and old 98abi symbols are still provided.
> However the c11 abi was broken (there are small number of packages
> that use c11 abi from before 5.x release).
> And finally newly compiled libraries against the new libstdc++ will
> use c11 abi, not 98abi.
> Depending on what those libraries export as an api, they may become
> incompatible (e.g. if they wrapped std::string, it will now become a
> different one).
>
> Do you have a list of libraries that e.g. google hangouts link
> against? if it only links against libstdc++ in 98abi it should
> continue to work.

Google Hangout was merely an example. I suppose we have several 
proprietary applications in Ubuntu Software Center too, that might 
suffer from the same problem?

Anyhow, it seems a little scary if there is a possibility that packages 
will be installable, but then randomly crash (or worse, cause a security 
hole) at runtime. Or is this fixed by versioning somehow, e g at Debian 
packaging level, file extension symlink level, or symbol linking level?

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic