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

[Rainer Orth]

Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:

> Jakub Jelinek <jakub@redhat.com> writes:
>
>> On Thu, May 23, 2013 at 10:56:25PM +0200, Rainer Orth wrote:
>>> >> I think std::chrono::steady_clock::now() needs to be protected with
>>> >> !(__sun__ && __svr4__) in GLIBCXX_3.4.17 since it only became available
>>> >> by default with Jonathan's patch.
>>> >
>>> > Ah, I see, gnu.ver has some
>>> > #ifdef HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT
>>> > #endif
>>> > guards there, does it work if you add it around the
>>> > GLIBCXX_3.4.17 std::chrono::steady_clock::now() definition?
>>> 
>>> If I do so, I would probably get an abi_check failure: with your patch,
>>> std::chrono::steady_clock::now() ends up in GLIBCXX_3.4.19 while it
>>> should appear in GLIBCXX_3.4.20 since this is new in GCC 4.9.
>>
>> In that case, either the --enable-libstdcxx-time=auto patch needs to be
>> backported to 4.8.1, or at least a small portion of it (do that auto thing
>> on Solaris only)?
>> Have steady_clock::now() as @GLIBCXX_3.4.17 + @@GLIBCXX_3.4.19 on Linux,
>> @@GLIBCXX_3.4.20 on Solaris, something else on other OSes would be quite
>> confusing.
>
> Agreed, that seems the best course of action if that's an option.

I just remembered that we aren't there yet even on mainline:

* This snippet

  http://gcc.gnu.org/ml/gcc-patches/2013-05/msg01255.html

  is necessary to avoid bootstrap failure on Solaris 9.

* We'll need to link every C++ program with -lrt on Solaris, as
  mentioned in the same message.  I suppose the best way to do this is
  along the lines of libgfortran.spec, rather than duplicate the
  necessary configury between g++ and libstdc++.  This might prove
  pretty invasive for the testsuite, though, and delay the 4.8.1 release
  quite a bit.

	Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University