C++11 enabling in F22?

Tom Hughes tom at compton.nu
Mon Oct 26 11:29:00 UTC 2015


On 26/10/15 11:23, Peter Robinson wrote:
> On Mon, Oct 26, 2015 at 11:13 AM, Marek Skalick√Ĺ <mskalick at redhat.com> wrote:
>> Hello everyone,
>> I would like to ask what do you think about enabling c++11 in library in
>> F22? Is it permitted by Fedora guidelines?
>>
>> I am asking because of this bug -
>> https://bugzilla.redhat.com/show_bug.cgi?id=1274307 . And I want to know
>> the opinion of someone else, to decide.
>
> It was explicitly not enabled in F-22 because it's not backwards
> compatible and required a mass rebuild for all c++ applications. It's
> enabled by default, and we had a mass rebuild as a result, in Fedora
> 23. As a result of the impact we won't be making such changes for a
> release that is long GA.

You're confusing two different things, though without knowing what that 
configure patch actually does we can't know what the answer is here.

There is, as far as I know, no problem using -std=c++11 in F22 or any 
other version of Fedora, it's just that the result might not be fully 
standards compliant.

Specifically in F22 there are two minor changes which require a change 
to the library ABI and as F22 was built with the old ABI you won't get 
those changes. Neither should affect whether code compiles and works though.

So the only thing you must not do in F22 is to set the define that 
selects the new ABI but you would probably find out quite quickly as you 
did as you would fail to link if you used any other C++ libraries that 
had been built with the old ABI.

Which is why I say we need to know what the configure flag does - my 
guess is that it just sets -std=c++11 which is fine. If it also sets the 
define to select the new ABI then that might be a problem.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/


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