compilers that support thread-local storage?

Ken Cunningham ken.cunningham.webuse at
Wed Feb 13 18:23:46 UTC 2019

__thread came first, then thread_local a bit later. 

the difference is that thread_local allows more complicated initializers and destructors ("non-trivial"). It is c++11, as you said.

quite old gcc versions support __thread  I think the earliest one was gcc 4.1 <>

gcc 4.8+  supports thread_local <>

For Open Source clang, we have this reference <> that shows clang-3.3+ supported it with a proper runtime. That runtime exists on 10.7+. As you know, I have recently enabled "emulated thread_local" on clang-5.0+ (to match up with the c++11 PG) for both stdlib=libc++ and stdlib=macports-libstdc++ (our c++11 runtimes). I wasn't planning on porting that back any further.

For Xcode clang, you already have that -- 900+. Apple introduced a better-performance thread_local system that (as I understand it) involved integration into dyld .

So gcc-4.8+ and clang-5.0+ is reliable on all systems using a c++11 runtime, although there are some systems that can use thread_local with clang-3.4 to clang-4.0 it appears (untested by me).

My idea was to make the cxx11 PG more or less == thread_local capability. 

This has _all_ been changed in base recently by Marcus' base PR #88, so it's a moving target.


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