[patch] Default to --enable-libstdcxx-time=auto

[Paolo Carlini]

Hi,

On 05/22/2013 11:59 AM, Jonathan Wakely wrote:
> On 22 May 2013 10:47, Paolo Carlini wrote:
>> Could you please double check abi_check? On this glibc 2.17 machine I'm
>> seeing:
>>
>> 1 incompatible symbols
>> 0
>> _ZNSt6chrono12steady_clock3nowEv
>> std::chrono::steady_clock::now()
>> version status: incompatible
>> GLIBCXX_3.4.17
>> type: function
>> status: added
>>
>> I'm going to try again, just in case I goofed something.
> No, I don't think you goofed, I see it too on glibc 2.17, sorry about that.
>
> How should we handle that export?  It is available on older systems
> without glibc 2.17 and with older GCC versions if you configure with
> --enable-libstdcxx-time=rt,
I don't think it could be available on older systems without something 
like --enable-libstdcxx-time=rt on the command line. That is, without a 
non-default configure switch. Anyway, indeed it could be available, 
depending on the configuration and we wanted it to be exported, in case. 
I think there isn't a risk of real, substantive abi-breakage here, the 
issue is largely about the way we are testing abi_check. I bet Jakub has 
ideas about the best way to approach this, like with the alias 
mechanism?!? Essentially we want to arrange things in such a way that 
this specific symbol is fine to be optionally exported at *any* version 
 >= GLIBCXX_3.4.17 (thus, no abi_check error), depending on the 
configure switch.

Paolo.