Re: [gentoo-dev] Re: RFC: c++14 global USE flag

[Maxim Koltsov]

2015-04-29 14:27 GMT+03:00 Anthony G. Basile <blueness@g.o>:

> On 04/28/15 17:52, Mike Gilbert wrote:
>
>> On Tue, Apr 28, 2015 at 4:07 PM, Anthony G. Basile <blueness@g.o>
>> wrote:
>>
>>> On 04/26/15 23:21, Duncan wrote:
>>>
>>>> Diego Elio Pettenò posted on Sun, 26 Apr 2015 17:41:04 +0100 as
>>>> excerpted:
>>>>
>>>>  On 25 April 2015 at 16:57, Duncan <1i5t5.duncan@×××.net> wrote:
>>>>>
>>>>>  Of course, one thing that could make the process faster would be if
>>>>>> C++
>>>>>> based packages were marked some way.
>>>>>>
>>>>>
>>>>> revdep-rebuild --soname 'libstdc\+\+.so.*'
>>>>>
>>>>> should do the trick. Stuff that does not link the library (statically
>>>>> linked or using libsupc++) should not really matter.
>>>>>
>>>> Thanks.  Obvious in hindsight. =:^)
>>>>
>>>>  just saw this.  This works unless you have two versions of gcc
>>> installed.
>>> The c++11 abi emitted by gcc-4.7 and 4.8 are different and since you link
>>> against the latest version (see the ordering of directories in
>>> /etc/ld.so.conf.d/05gcc-x86_64-pc-linux-gnu.conf), building with the
>>> earlier
>>> gcc can cause breakage.  We may not want to support such a situation but
>>> I'd
>>> like to.
>>>
>> As I understand it, a given version of gcc links objects against its
>> own version of libstdc++, but the "latest" version of libstdc++ is
>> loaded by ld.so at runtime.
>>
>> Maybe that's what you meant, but I wanted to clarify that. And if I am
>> wrong on that, please correct me. ^_^
>>
>>
> Yes.  So you could, for example, fix this by setting the correct rpath at
> link time so the correct library gets loaded at runtime.


I fear this discussion is going in a slightly wrong direction. I'm not
going to make any global Gentoo changes, I just need to add support for
C++14 mode in a bunch of packages I maintain, and for that, I need to
decide on a place to store USE descriptions. If I won't get good options,
I'll just go and add this description to every of ~70 metadata's.
Please consider the patch I'm going to apply to our eclass:

 https://bpaste.net/show/39ec6f4760f4

This is intended as an experimental feature, not as a globally supported
configuration for every package in Gentoo. This is needed because already
now LeechCraft has some functionality that is implemented in C++14 and
won't be available otherwise.

Please give your opinion on where to put this USE desc, that's all I want :)


> --
> Anthony G. Basile, Ph.D.
> Gentoo Linux Developer [Hardened]
> E-Mail    : blueness@g.o
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> GnuPG ID  : F52D4BBA
>
>