Re: [gentoo-dev] How to support C++11 in libraries?

[C. Bergström]

On 12/19/13 03:35 PM, Michał Górny wrote:
> Dnia 2013-12-19, o godz. 15:28:46
> "C. Bergström" <cbergstrom@×××××××××.com> napisał(a):
>
>> On 12/19/13 03:20 PM, Michał Górny wrote:
>>> Dnia 2013-12-19, o godz. 00:56:31
>>> "C. Bergström" <cbergstrom@×××××××××.com> napisał(a):
>>>
>>>> On 12/19/13 12:47 AM, Kent Fredric wrote:
>>>>> On 19 December 2013 06:33, Jan Kundrát <jkt@g.o> wrote:
>>>>>> I'm worried by the cost of such a policy, though, because we would suddenly
>>>>>> have to patch some unknown amount of software
>>>>> Given the nature that changing that CXX Flag globally for all users
>>>>> could cause many packages to spontaneously fail to build, wouldn't
>>>>> that imply that changing that flag would essentially be de-stabilizing
>>>>> the whole tree, and a package being (arch) would no longer be an
>>>>> indication of sane, tested behaviour?
>>>>>
>>>>> This is really the perk of the USE driven process, the granular
>>>>> piecemeal approach that does only as much as necessary, without
>>>>> changing things that are already stable.
>>>> In practice wouldn't that mean you'd have to add c++11 USE flag to every
>>>> C++11 application and lib?
>>> No. Only the libs that change their ABI in C++11.
>>>
>>>> "Best case" both build and you end up with a linker problem (can be
>>>> worked around with compiler patches)
>>>> /usr/lib64/libboost.so
>>>> /usr/lib64-c++11/libboost.so
>>> What's wrong with this solution:
>>>
>>> 1. distro-specific compiler patching is wrong,
>> Pragmatically, this needs to be upstream and should have been there
>> already. Get some feedback to see if gcc people are receptive to the
>> idea before testing a gentoo-only patch. If they accept it upstream -
>> backport it. If they tell you f* off - get their feedback on how to deal
>> with it - more belo
>>
>> (this is not a gentoo only problem - this discussion should happen on a
>> more global level...)
> And how is this an issue to the major distributions? Binary distros can
> do a simple switch with standard all-package upgrade and forget about
> it. Like they usually do. Only people who built from sources have to
> think about it.
Umm..  no? Lets use a hypothetical example...

libboost.so (or any really popular lib.. Qt..) built with -std=c++11 
breaks abi

If they don't do some sort of multilib approach - they are only going to 
build it once and then any consumer of that outside the distro is stuck 
with their decision. That's probably fine in the predominately C++03 
world we have today, but for how long? I expect users on the binary 
distro just do what they have to work around the problem (go build their 
whole dependency chain from source). It didn't solve the problem - just 
made it work for distro packages and pushed it off to the user.

My -L rant would depend on the above being used - that's all