Fix struct sigaltstack namespace (bug 21517)

[Khem Raj]

On Sat, Jun 3, 2017 at 8:55 AM, Florian Weimer <fweimer@redhat.com> wrote:
> On 05/25/2017 12:32 AM, Joseph Myers wrote:
>> +* The stack_t type no longer has the name struct sigaltstack.  This changes
>> +  the C++ name mangling for interfaces involving this type.
>
> I checked Fedora and we don't seem to have any ABI impact from this
> change (no exported symbols matching /^_Z.*sigaltstack/), so this is
> probably fine.

I think gcc sanitizers will have issues since they are using
the forward declaration of sigaltstack

see
https://github.com/gcc-mirror/gcc/blob/master/libsanitizer/sanitizer_common/sanitizer_linux.h#L22

>
> Thanks,
> Florian