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Re: Mandates explicit -std=c++XY for c++ projects

On 10 October 2017 at 14:07, Gert Wollny <gw.fossdev@xxxxxxxxx> wrote:
> Hello Mathieu,
> Am Dienstag, den 10.10.2017, 11:45 +0200 schrieb Mathieu Malaterre:
> [...]
> I don't think there is much to gain from it. Whenever there is a
> change
>> > in the major version of gcc/g++ many bugs show up and all involved
>> > really do a great job fixing these. IMHO switching from an older
>> > C++ standard to a newer one is no different. In fact, I think that
>> > this forced change is an excellent incentive to review older
>> > packages.
>> Right. I have the exact opposite view: why compile a c++ project
>> using c++11 flags while it was written for c++98...
> Like I pointed out I think it is somewhat the same like with new
> compilers: New compilers interpret the standard more strict, optimize
> differently, and hence, we get build failures and test failures that we
> need to fix. The same it is when moving from one standard to the next.
> You also consider that upstream is active and willing to migrate from
>> c++98 toward c++11 (for example), I had the exact opposite example in
>> mind.
> I think nobody would object if you set the flag to -std=c++98 for a
> certain package, especially if upstream is dead or unwilling to move to
> a newer standard, but I wouldn't want to see it as the default.

We, as a distribution, are better than that. Please provide URLs to
FTBFS with c++11 bug report that is of concern for you, and I will try
to look into it to fix the FTBFS with a distro patch.

> [...]
>> > I think we should strife for all packages using the
>> > same C++ standard, and this should be the default of the currently
>> > used C++ compiler. Forcing a lower standard on a package as a
>> > maintainer I would consider only as a (temporal) workaround to fix
>> > RC bugs, and preferable only for leaf packages.
>> I do not see you point clearly. Let me rephrase it then: You would
>> like to see no explicit -std=c++ in the build logs, so as to
>> guarantee we always compile a c++ project using whatever default c++
>> standard is being used by the current gcc version. Is this a correct
>> rephrasing ?
> Yes.
> I wouldn't mind, though, if there was some output from the compiler
> that indicates what standard was used to compile a package, but that's
> different from setting a standard explicitly.
> Best,
> Gert