[RFC] 12658_thread.cc randomly fails (on MP machines)

[Paolo Carlini]

Hi,

I'm trying to understand more about this issue: as you may have
noticed already, on multiprocessor machines the testcase randomly
fails. This happens both for mainline and 3_4-branch.

Backtraces on a 4-way x86_64 machine show that the problem seems
*not* due to locale::locale() and locale::global(const locale&),
which appear indeed fixed: the testcase stresses the MT-safety of
the locale implementation *well* beyond what originally reported
in libstdc++/12658.

Honestly, it's not completely clear to me what we really want to
achieve: if it's complete MT-safety in locale then the two issues
discussed in 12658 seem only the "tip of the iceberg", sadly...

If, less ambitiously (at least for now!) we want only MT-safety
in dealing with the global locale, then probably we are already
quite close but we badly need a different, much simpler, testcase
than 12658_thread.

Opinions? Ideas? Patches? ;)

Thanks,
Paolo.