c - Visual Studio C 的 _Thrd_create() 和其他线程函数是 Thrd_ C11 函数的实现吗？

Question

Visual Studio 2017 几乎没有 C99 和 C11 语言支持，但在某些领域，它似乎具有相似的底层原语，但具有原语名称的修改版本。

具体来说，我正在研究 C11 的多线程库的支持。

在查看包含文件 thr/xthreads.h 时，大多数 C11 多线程库原语都可用，但函数名称以下划线作为前缀。换句话说，thrd_create()是_Thrd_create()，并且包含文件threads.h不存在，但thr/xthreads.h 确实如此。

阅读 Herb Sutter 发表于 2012 年 5 月 3 日的博文，Reader Q&A: What about VC++ and C99? ，看来微软几乎没有计划在 Visual Studio 中实现 C99 或 C11，尽管互联网上的其他评论和问题表明这一立场自 2012 年以来可能已经发生了变化。

持续支持包含文件 thr/xthreads.h 中声明的多线程库的可能性有多大？

我有什么保证这些原语将在 Visual Studio 2019 及更高版本中得到维护？是否有关于 Microsoft Visual Studio 计划的任何其他信息？

在 Visual Studio 2017 中创建 Windows 控制台应用程序后，我将以下简单示例放在 .c 扩展源文件中。 main() 位于 .cpp 源文件中，由以下部分组成对下面的 func() 函数的调用:

#include <stdio.h>
#include <thr/xthreads.h>    //  access the underlying C11 threads library.

typedef struct {
    int ik;
    int ij;
    _Thrd_t *p;
} Thing;

int tx1 ( void * y)
{
    Thing * x = (Thing *)y;
    xtime xTimeAmt = {0};


    printf("One this is thread %d  %d\n", x->ik, x->ij);

    _Thrd_yield();

    xtime_get(&xTimeAmt, TIME_UTC);

    xTimeAmt.sec += 5;         // wait 5 seconds
    _Thrd_sleep(&xTimeAmt);

    printf("Two this is thread %d  %d\n", x->ik, x->ij);

    return 0;
}

_Thrd_t tt1;
_Thrd_t tt2;
_Thrd_t tt3;

int func(void)
{
    Thing t1 = { 1, 10 };
    Thing t2 = { 2, 20 };
    Thing t3 = { 3, 30 };
    int   rt1, rt2, rt3;

    for (int i = 3; i < 10; i++) {
        printf("i = %d\n", i);
    }

    _Thrd_create((t1.p = &tt1), tx1, &t1);
    _Thrd_create((t2.p = &tt2), tx1, &t2);
    _Thrd_create((t3.p = &tt3), tx1, &t3);

    _Thrd_join(tt1, &rt1);
    _Thrd_join(tt2, &rt2);
    _Thrd_join(tt3, &rt3);

    for (int i = 23; i < 30; i++) {
        printf("i = %d\n", i);
    }

    return 0;
}

该程序的输出是:

i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9
One this is thread 1  10
One this is thread 2  20
One this is thread 3  30
Two this is thread 1  10
Two this is thread 3  30
Two this is thread 2  20
i = 23
i = 24
i = 25
i = 26
i = 27
i = 28
i = 29

Answer 1

How likely is there to be continued support for the multi-threading library declared in the include file thr/xthreads.h?

不太可能。

What assurances do I have that these primitives will be maintained in Visual Studio 2019 and later?

没有。

Is there any other information available as to Microsoft plans for Visual Studio?

嗯，如the standard states :

Each identifier that contains a double underscore __ or begins with an underscore followed by an uppercase letter is reserved to the implementation for any use.)

您永远不应该依赖他们的任何行为。引用a relevant MS bug report :

Like all underscore-capital _Ugly machinery, such bits may be added, changed, and removed in any update (unless the machinery is a specifically documented exception, like _ITERATOR_DEBUG_LEVEL, or basic_string::_Copy_s).

他们还说明了您应该做什么:

You should call documented APIs, like std::thread or _beginthreadex, instead.