如何将变量声明为线程局部可移植？ [英] How to declare a variable as thread local portably?

问题描述

C11引入了 _Thread_local 存储类说明可在联合与静态和<$ C $使用C> EXTERN 存储类声明来声明一个变量作为线程局部。 GNU C编译器套件实现了存储类说明 __线程用相同的相同的语义。

不幸的是我没有找到任何编译器（我试过GCC，铛和太阳录音室），真正实现 _Thread_local 关键字。我目前使用下面的结构来声明一个关键字 thread_local ：

  / *从GCC还C11不知道_Thread_local * /
#IFDEF __GNUC__
＃定义thread_local __thread
#elif指令__STDC_VERSION__＆GT; = 201112L
＃定义thread_local _Thread_local
＃其他
＃错误不知道如何定义thread_local
＃万一
 

我知道这可能不与MSVC和其他编译器。任何人都可以建议我一个更好的方法，在某种程度上，它的作品在尽可能多的编译器尽可能声明 thread_local ？

修改

克里斯托夫建议微软的Visual C允许 __ declspec（线程）。这是更新的宏定义：

  / *从GCC还C11不知道_Thread_local * /
#IFDEF __GNUC__
＃定义thread_local __thread
#elif指令__STDC_VERSION__＆GT; = 201112L
＃定义thread_local _Thread_local
#elif指令定义（_MSC_VER）
＃定义thread_local __declspec（线程）
＃其他
＃错误不能定义thread_local
＃万一
 

解决方案

维基百科的<信息/ A>与，我想出了以下（未经测试）版本的编译器宏这个名单

 的#ifndef thread_local
＃如果__STDC_VERSION__＆GT; = 201112＆放大器;＆安培; ！定义__STDC_NO_THREADS__
＃定义thread_local _Thread_local
＃ELIF定义_WIN32＆放大器;＆安培; （\\
       定义_MSC_VER || \\
       定义__ICL || \\
       定义__DMC__ || \\
       定义__BORLANDC__）
＃定义thread_local __declspec（线程）
/ *注意，ICC（Linux版）和锵被覆盖__GNUC__ * /
＃ELIF定义__GNUC__ || \\
       定义__SUNPRO_C || \\
       定义__xlC__
＃定义thread_local __thread
其他＃
＃错误无法定义thread_local
＃ 万一
＃万一
 

C11 introduces the _Thread_local storage class specifier that can be used in combination with the static and extern storage class specifiers to declare a variable as thread local. The GNU C compiler suite implements a storage class specifier __thread with the same same semantics.

Unfortunately I did not find any compiler (I tried gcc, clang and SUN studio) that actually implements the _Thread_local keywords. I currently use the following construct to declare a keyword thread_local:

/* gcc doesn't know _Thread_local from C11 yet */
#ifdef __GNUC__
# define thread_local __thread
#elif __STDC_VERSION__ >= 201112L
# define thread_local _Thread_local
#else
# error Don't know how to define thread_local
#endif

I know that this probably does not work with MSVC and other compilers. Can anybody suggest me a better method to declare thread_local in a way that it works in as many compilers as possible?

Edit

Christoph suggested that Microsoft Visual C allows __declspec(thread). This is the updated macro definition:

/* gcc doesn't know _Thread_local from C11 yet */
#ifdef __GNUC__
# define thread_local __thread
#elif __STDC_VERSION__ >= 201112L
# define thread_local _Thread_local
#elif defined(_MSC_VER)
# define thread_local __declspec(thread)
#else
# error Cannot define thread_local
#endif

解决方案

Combining information from Wikipedia with this list of compiler macros, I came up with the following (untested) version:

#ifndef thread_local
# if __STDC_VERSION__ >= 201112 && !defined __STDC_NO_THREADS__
#  define thread_local _Thread_local
# elif defined _WIN32 && ( \
       defined _MSC_VER || \
       defined __ICL || \
       defined __DMC__ || \
       defined __BORLANDC__ )
#  define thread_local __declspec(thread) 
/* note that ICC (linux) and Clang are covered by __GNUC__ */
# elif defined __GNUC__ || \
       defined __SUNPRO_C || \
       defined __xlC__
#  define thread_local __thread
# else
#  error "Cannot define thread_local"
# endif
#endif

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