Segfault in _Unwind_* code called from pthread_exit

[Tijl Coosemans]

On Tue, 31 Oct 2017 22:52:33 +0100 Andreas Tobler <andreast-list at fgznet.ch> wrote:
> On 31.10.17 22:36, Gerald Pfeifer wrote:
>> On Tue, 31 Oct 2017, Andreas Tobler wrote:
>> Those possibly still stuck on obsolete versions of FreeBSD don't
>> need/want fancy new compilers and GCC 4.9 is still available for
>> use and does not exhibit this issue, correct?  (If it does, nobody
>> reported any problems.)
> 
> It is limited to gcc >=5, gcc-4.9 does not have the 
> MD_FALLBACK_FRAME_STATE_FOR defined.
> 
>>> I can 'ifdef' the new code and in the 'else' case we fall back to
>>> the already existing path.
>> 
>> If it's "cheap", that might be nice.
> 
> Attached, the test is running on gcc trunk and gcc-6. gcc-6 is the last 
> one with java support and there we have quite extensive test cases which 
> really test for this MD_FALLBACK_FRAME_STATE_FOR macro. These test 
> cases, Throw_2 and co do pass. So I think the new bits should be fine.
> Also some coming asan test cases do pass with this addition too.

Please commit it to the ports tree as well, because there are reports
that ftp/curl can trigger the problem.