xcode c++ 线程本地存储 clang-503.0.40 (Mac OSX)
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c++ thread-local storage clang-503.0.40 (Mac OSX)
提问by pier94
After I declared a variable in this way:
在我以这种方式声明一个变量之后：
#include <thread>
namespace thread_space
{
thread_local int s;
} //etc.
i tried to compile my code using 'g++ -std=c++0x -pthread [sourcefile]'. I get the following error:
我尝试使用“g++ -std=c++0x -pthread [sourcefile]”编译我的代码。我收到以下错误：
example.C:6:8: error: thread-local storage is unsupported for the current target
static thread_local int s;
^
1 error generated.
If i try to compile the same code on Linux with GCC 4.8.1 whit the same flags, i get a functioning executable file. I'm using clang-503.0.40 (the one which comes with Xcode 5.1.1) on a MacBook Pro running OSX 10.9.3. Can anybody explain me what i'm doing wrong? Thank you!!
如果我尝试在带有相同标志的 GCC 4.8.1 的 Linux 上编译相同的代码，我会得到一个正常运行的可执行文件。我在运行 OSX 10.9.3 的 MacBook Pro 上使用 clang-503.0.40（Xcode 5.1.1 附带的那个）。谁能解释一下我做错了什么？谢谢！！
采纳答案by Thomas
Try clang++ -stdlib=libc++ -std=c++11. OS X's outdated libstdc++ doesn't support TLS.
试试clang++ -stdlib=libc++ -std=c++11。OS X 过时的 libstdc++ 不支持 TLS。
Edit
编辑
Ok, this works for the normal clang version but not for the Xcode one.
好的，这适用于普通的 clang 版本，但不适用于 Xcode 版本。
I did a diff against Apple's clang (503.0.38)and the normal released oneand found the following difference:
我对Apple 的 clang (503.0.38)和正常发布的做了一个比较，发现以下区别：
.Case("cxx_thread_local",
- LangOpts.CPlusPlus11 && PP.getTargetInfo().isTLSSupported() &&
- !PP.getTargetInfo().getTriple().isOSDarwin())
+ LangOpts.CPlusPlus11 && PP.getTargetInfo().isTLSSupported())
So I think this is a bug in Apple's clang version (or they kept it in there on purpose - but still weird, because -vsays based on 3.4).
所以我认为这是 Apple 的 clang 版本中的一个错误（或者他们故意将它保留在那里 - 但仍然很奇怪，因为-v说基于 3.4）。
回答by glampert
Alternatively, you can use compiler extensions such as __thread(GCC/Clang) or __declspec(thread)(Visual Studio).
或者，您可以使用编译器扩展，例如__thread(GCC/Clang) 或__declspec(thread)(Visual Studio)。
Wrap it in a macro and you can easily port your code across different compilers and language versions:
将它包装在一个宏中，您可以轻松地将代码移植到不同的编译器和语言版本中：
#if HAS_CXX11_THREAD_LOCAL
#define ATTRIBUTE_TLS thread_local
#elif defined (__GNUC__)
#define ATTRIBUTE_TLS __thread
#elif defined (_MSC_VER)
#define ATTRIBUTE_TLS __declspec(thread)
#else // !C++11 && !__GNUC__ && !_MSC_VER
#error "Define a thread local storage qualifier for your compiler/platform!"
#endif
...
ATTRIBUTE_TLS static unsigned int tls_int;
回答by rsfinn
The clang compiler included in the Xcode 8 Beta and GM releases supports the C++11 thread_localkeyword with both -std=c++11and -std=c++14(as well as the GCC variants).
Xcode 8 Beta 和 GM 版本中包含的 clang 编译器支持 C++11thread_local关键字和-std=c++11和-std=c++14（以及 GCC 变体）。
Earlier versions of Xcode apparently supported C-style thread local storage using the keywords __threador _Thread_local, according to the WWDC 2016 video "What's New in LLVM"(see the discussion beginning at 5:50).
根据WWDC 2016 视频“LLVM 中的新功能”（参见 5:50 开始的讨论），早期版本的 Xcode 显然支持使用关键字__threador 的C 样式线程本地存储。_Thread_local
回答by C. Scott Ananian
Seems like you might need to set the minimum OS X version you target to 10.7 or higher.
似乎您可能需要将目标的最低 OS X 版本设置为 10.7 或更高版本。
