std::locale 取得所有权

Question

我有下一个代码：

 boost::posix_time::time_facet facet("%Y-%m-%dT%H:%M:%f");
 std::stringstream ss;
 ss.imbue(std::locale(ss.getloc(), &facet));

当我运行这段代码时，编译器似乎试图在 ss 析构函数调用期间释放 facet（调试器说的）。

当我运行这段代码时：

 std::stringstream ss;
 ss.imbue(std::locale(ss.getloc(), new boost::posix_time::time_facet("%Y-%m-%dT%H:%M:%f")));

好的。

所以，我想知道是否存在关于此行为或 local 取得所有权的原因的任何文档。我试图找出解释，但文档中没有任何内容。

std::locale() 是否拥有 time_facet？

Answer 1

http://en.cppreference.com/w/cpp/locale/locale/locale

template< class Facet > locale( const locale& other, Facet* f ); (7)

Overload 7 is typically called with its second argument, f, obtained directly from a new-expression: the locale is responsible for calling the matching delete from its own destructor.

在http://eel.is/c++draft/locale.facet#3中还有另一个提示：

The refs argument to the constructor is used for lifetime management. For refs == 0, the implementation performs delete static_cast(f) (where f is a pointer to the facet) when the last locale object containing the facet is destroyed; for refs == 1, the implementation never destroys the facet.

由此可见，facet（以及派生的类）中存在内部引用计数机制。这或多或少意味着你传递给 locale 的 facet 是与它共享的，如果你不显式地增加它的引用计数，它将被销毁，因为传递一个指向它的指针不能增加重新计数。

std::locale 取得所有权

std::locale take ownership

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