C ++ 11标准是否正式定义了获取，释放和消费操作？ [英] Does the C++11 standard formally define acquire, release, and consume operations?

问题描述

在C ++ 11标准中，1.10 / 5节提到，但没有正式定义术语获取操作， code>和消费操作。然后在第29节中继续使用这些术语来描述某些内存排序，原子操作和内存栅栏的操作。例如，订单和一致性中的29.3 / 1表示：

In the C++11 standard, section 1.10/5 mentions, but does not formally define the terms acquire operation, release operation, and consume operation. It then goes on in Section 29 to use these terms to describe the actions of certain memory orderings, atomic operations, and memory fences. For instance, 29.3/1 on "Order and Consistency" states:

memory_order_release ， memory_order_acq_rel 和 memory_order_seq_cst ：存储操作对受影响的内存位置执行释放操作 [强调添加]。

memory_order_release, memory_order_acq_rel, and memory_order_seq_cst: a store operation performs a release operation [emphasis added] on the affected memory location.

这种类型的语言在第29节中被重复，但是它让我感到烦恼， memory_order 枚举的所有含义都是基于

This type of language is repeated throughout section 29, but it bothers me a bit that all meanings for the memory_order enumerations are based on operation types that themselves do not seem to be formalized by the standard, yet must have some commonly agreed-to meaning for them to be effective as definitions.

使用不同的方法来实现自定义操作类型，它们本身似乎不被标准正式化，但必须具有一些共同的含义，以使它们作为定义有效。 ，如果我说一个条是一个翻转的foo， bar 和 foo 的具体含义是不明确的，因为这两个术语都没有正式定义。

Put a different way, if I said "A bar is a flipped foo", the concrete meaning of bar and foo are ambiguous since neither term is formally defined. Only their relative natures are defined.

C ++ 11标准或其他C ++ 11标准委员会文件是否正式定义了一个获取操作，发布操作等，或者是这些简单的通常理解的术语？如果后者，是否有一个好的参考，被认为是这些操作的意义的行业标准？我特别问，因为硬件内存一致性模型不是相等的，因此我想要有一些通常同意的参考，允许实现编译器等正确地将这些操作的语义转换为本机汇编命令。 / p>

Does the C++11 standard, or some other C++11 standards committee document formally define what exactly an acquire operation, release operation, etc. is, or are these simply commonly understood terms? If the latter, is there a good reference that is considered an industry standard for the meaning of these operations? I specifically ask because hardware memory consistency models are not created equal, and therefore I'm figuring there must be some commonly agreed-to reference that allows those implementing compilers, etc. to properly translate the semantics of these operations into native assembly commands.

推荐答案

在其中一个注释中有一个非正式的汇总定义：

There's an informal summarized definition given in one of the notes:

在上执行发布操作A 强制对其他内存位置的先前副作用变为对其他线程可见，以后执行消耗或获取操作

performing a release operation on A forces prior side effects on other memory locations to become visible to other threads that later perform a consume or an acquire operation on A.

除此之外，获取和释放操作的行为在1.10中完全定义，特别是它们如何促成发生在之前的关系。除了行为之外的任何定义都是无用的。

Besides that, the behavior of acquire and release operations is fully defined in 1.10, specifically in how they contribute to happens-before relationships. Any definition apart from behavior is useless.

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