在C ++中获取所有权和释放对象的语法准则 [英] Syntax guidelines for taking ownership and releasing objects in C++

问题描述

我想知道 - 有关于C ++（非）成员函数的语法的任何指导，允许我理解（无论如何，如果可能的话）其参数和返回值的所有权策略。

I want to know - are there any guidelines about syntax of C++ (non-)member functions, that allows me to understand (without comments, if possible) the ownership policy of its arguments and return value. By ownership I mean, that the owner is responsible for the destruction of the owned object.

我区分以下关于参数的规则：

I distinguish the following rules about arguments:

• 取得所有权


• 不占有所有权


• 分享

和关于返回值：

<在此群组中）

• 不发布


• 分享

例如，通过引用传递对象不会取得所有权：

For example, passing object by reference doesn't take it's ownership:

void func(object & obj) { ... }

这样的指南可以使用标准结构，如unique_ptr，shared_ptr等。

Such guidelines may use standard constructions like unique_ptr, shared_ptr, etc. If there are no such guidelines, then the examples of possible syntax misunderstandings are welcome too.

推荐答案

我不明白为什么要使用智能指针不够。我不能想到任何其他我不会归类为代码气味。在原始指针上使用智能指针使所有权和响应能力完全清楚：

I can't see why using smart pointers doesn't suffice. I can't think of anything else that I wouldn't categorize as code smell. Using smart pointers over raw pointers makes ownership and responsebilities perfectly clear:

• auto_ptr unique_ptr - 单个所有者，所有权已转移


• shared_ptr


• 
  
• scoped_ptr - 单个拥有者，无法转移所有权
c $ c> weak_ptr - observer（但是 shared_ptr 可以从 weak_ptr ）创建

• auto_ptr/unique_ptr - single owner, ownership is transferred
• shared_ptr - multiple owners, ownership may be transferred
• scoped_ptr - single owner, ownership cannot be transferred
• weak_ptr - observer (but shared_ptr may be created from weak_ptr)

我认为这些足以清楚地显示责任，例如

I think that these suffice to clearly show the responsibilities, e.g.

void func(std::auto_ptr<Class> input) {...} // func() takes ownership of input
void func(std::shared_ptr<Class> input) {...} // func() and caller share ownership
std::auto_ptr<Class> func() {...} // caller takes ownership of returned value
std::shared_ptr<Class> func() {...} // func() and caller shares ownership of returned object
std::weak_ptr<Class> func() {...} // func() owns created object, but caller may observe it

正如你所提到的，在这个意义上，引用也很大。注意，如果需要使用一些自定义机制释放指针， shared_ptr 和 unique_ptr 支持自定义删除程序。 auto_ptr 没有此功能。

As you mention, references are also great in this sense. Note if there's a need to free the pointers using some custom mechanism, shared_ptr and unique_ptr supports custom deleters. auto_ptr does not have this capability.

注意！如果你使用的是C ++ 11之前的版本，你必须使用 boost :: shared_ptr 和 boost：weak_ptr 。

Note! If you are using C++ pre-11, you'll have to resort to boost::shared_ptr and boost:weak_ptr.

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