CODEWITHSUNDEEP
c++c++11visual-c++gccclang
Prismatic
Prismatic

Reputation: 3348

What is the current state of support for 'thread_local' across platforms?

I'd like a summary of what the current state of support for the 'thread_local' keyword is across different compilers and platforms.

I'm specifically interested in common desktop and mobile platforms. The information I could find seems spotty at best with reports of it working on some platforms and not on others or mentions of support being a WIP. Answers that confirm support (or lack of support) even for single platforms are welcome. Please mention any caveats to the support if there are any.

Upvotes: 13

Views: 3100

Answers (3)

legends2k
legends2k

Reputation: 32884

GCC + *nix

GCC supports thread-local storage (thread_local storage duration specifier) since GCC 4.8 i.e. since 2013 March on Linux, macOS and other Unix-likes.

GCC + Windows (MinGW)

On Windows, MinGW (Thread model: POSIX) however has a bug: thread_local destructors broken with posix threading since 2015 which makes it still not easy to create thread-local variables on Windows. This includes GCC's extension of using __thread storage specifier on MinGW.

Upvotes: 1

Christophe
Christophe

Reputation: 73366

In complement to the other excellent answer: MSVC 2013 doesn't currently support it.

This page on support of core language features claims it's partially supported. However, looking at the details it appears that:

Thread-local storage is listed as "Partial" because VC has provided the non-Standard extension __declspec(thread) for many years. (Notably, C++11 thread_local supports non-PODs, but __declspec(thread) doesn't.)

It's implemented in MSVC 2014 CTP 3 (since summer 2014; See blog entry) and is available in MSVS2015.

Upvotes: 8

Carl Norum
Carl Norum

Reputation: 224834

For clang, you can check the C++11 implementation status:

Language Feature: Thread-local storage
C++11 Proposal: N2659
Available in Clang? Clang 3.3

and

Clang 3.3 and later implement all of the ISO C++ 2011 standard. ... thread_local support currently requires the C++ runtime library from g++-4.8 or later.

You could also use libc++, which is "a 100% complete C++11 implementation on Apple's OS X."

Upvotes: 3

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