[MacPorts] #52585: libcxxabi -- attempts to add thread-local-storage (TLS) to <10.9

[MacPorts]

#52585: libcxxabi -- attempts to add thread-local-storage (TLS) to <10.9
-------------------------------------+--------------------------------
 Reporter:  ken.cunningham.webuse@…  |      Owner:  macports-tickets@…
     Type:  defect                   |     Status:  new
 Priority:  Normal                   |  Milestone:
Component:  ports                    |    Version:  2.3.4
 Keywords:                           |       Port:  libcxxabi
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 As per the mailing list discussion, a few ports are requesting TLS which
 is not available on systems prior to 10.9. This functionality is
 implemented in libcxxabi, and there are current efforts to provide a
 fallback mechanism for this detailed on the llvm website's libcxxxabi
 pages. < https://reviews.llvm.org/D21803>.

 This ticket hopes to follow the attempts to get this to work.

 First thing I notice is that the patches above appear to apply to
 libcxxabi @3.9.0, and we're currently running @3.7.0. I first tried to
 build @3.9.0 by updating the portfile, but ran into some attempts to
 rebuild clang-3.7 which I assume to be the dependency cycle mentioned in
 the libcxxabi portfile. I could drop back to clang-3.4 and try to build
 it, I presume -- but rather than do that, I attempted to backport the
 changes into libcxxabi @3.7.0 instead.

 Almost all the changes are in one file, src/cxa_thread_atexit.cpp, which
 is basically completely rewritten. I was unable to apply the patch from
 the website cleanly due to changes in that file from @3.7.0, so I did it
 manually, and hopefully without error. The changes cxa_thread_atexit.cpp
 file is attached.

 Sadly, when building the replacement libcxxabi that is supposed to provide
 a fallback for TLS, I now get the error saying to build the file, the
 system requires TLS -- which of course is sort of a catch-22.

 So, working on that idea further while I post progress so far.

-- 
Ticket URL: <https://trac.macports.org/ticket/52585>
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