I've run into this again tonight.
I'm using, at this moment, clang-3.7 / llvm-3.7 with macports-created libc++
and libc++abi.
Every once in a while, a port I'm trying to create or build will error out due
to this:
error: thread-local storage is not supported for the current target
/opt/local/var/macports/build/_opt_myports_devel_glbinding/glbinding/work/build/source/glbinding/include/glbinding/glbinding_features.h:240:36:
note: expanded from macro 'GLBINDING_THREAD_LOCAL'
# define GLBINDING_THREAD_LOCAL __thread
^
In this case, I'm trying to create this port
<https://github.com/cginternals/glbinding> which is a dev library for openGL.
As I understand it, thread_local storage is a feature of cxx11 that should be -
but apparently isn't - supported by clang / llvm.
This page <http://clang.llvm.org/cxx_status.html#n2659> says it is enabled in
clang-3.3, if your c++ runtime provides __cxa_thread_atexit, like libc++abi 3.6
or later.
I have libcxxabi @3.7.0_1+universal (active) platform='darwin 10' archs='i386
x86_64'
there's a thread on stackoverflow about it:
<http://stackoverflow.com/questions/28094794/why-does-apple-clang-disallow-c11-thread-local-when-official-clang-supports>
which has this quote:
For Xcode 7.x and earlier, here is an answer from 2014 from an Apple engineer
on the Apple Developer Forum:
We don't support the thread_local implementation from the open-source Clang
because we believe we can provide a higher-performance implementation for our
platforms using various features in the dynamic linker. Such an implementation
would be ABI-incompatible with the implementation in the open-source Clang, so
we won't support thread_local until we get an implementation we can live with
for the foreseeable future.
There are many smart people on this list who know a lot more about this kind of
thing than I ever will.
Anyone offer any insight into this issue?
best,
Ken
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