C ++ 20 constexpr容器将如何工作？ [英] How will C++20 constexpr containers work?

问题描述

为 constexpr std :: string 和 constexpr std :: vector 已被C ++ 20接受，如何使用它们？链接的文件在细节上很短。我们是否需要指定特殊的 constexpr 分配器，使编译时字符串/向量与它们的常规等效项不兼容？

As constexpr std::string and constexpr std::vector have been accepted into C++20, how will these be used? The linked papers are very short on details. Do we need to specify special constexpr allocators, making compile-time strings/vectors incompatible with their normal equivalents?

推荐答案

这两篇论文在很大程度上取决于 P0784 ，其中讨论了如何在编译时分配-时间会起作用。

Those two papers depend heavily on P0784, which discusses how allocations at compile-time will work.

不完整的答案：

• 仅 std :: allocator 将起作用。


• 所有分配都将被跟踪，并且必须在编译完成之前将其释放。这意味着您可以在编译时进行操作，但是不能将 string 和 vector 变量初始化为在运行时使用。 （个人而言，我认为很有可能在将来的标准版本中取消此限制-但这只是我的意见。）

• Only std::allocator will work.
• All allocations are tracked, and must be deallocated before compilation is complete. This means that you can do manipulations at compile-time, but you can't initialize string and vector variables to be used at run-time. (Personally, I think there's a good chance that this restriction will be lifted in a future version of the standard - but that's just my opinion.)

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