A constant initializer for an object
ois an expression that is a constant expression,except that it may also invoke constexpr constructors foroand its subobjects even if those objects are of non-literal class types [Note: such a class may have a non-trivial destructor — end note]. Constant initialization is performed […] if an object with static or thread storage duration is initialized by a constructor call,and if the initialization full-expression is a constant initializer for the object […]
典型的例子是std :: unique_ptr,“手写不应该更糟”：
std::unique_ptr<int> p; // statically initialized by [unique.ptr.single.ctor],// requires no code excution
int main()
{
p = std::make_unique<int>(100);
}
// p is destroyed eventually
在添加之前,静态初始化的变量是引用类型或文字对象类型,因此具有微不足道的析构函数.但现在静态初始化的全局变量可以有一个非平凡的析构函数.
解决方法
If an object is initialized statically,the object is destroyed in the@H_403_32@ same order as if the object was dynamically initialized.
和
If the completion of the constructor or dynamic initialization of an@H_403_32@ object with static storage duration is sequenced before that of@H_403_32@ another,the completion of the destructor of the second is sequenced@H_403_32@ before the initiation of the destructor of the first.
现在,
Static initialization shall be performed before any dynamic@H_403_32@ initialization takes place.
显然,这回答了第一个问题：由于p被保证在执行任何动态初始化之前初始化,所以在任何动态初始化的对象被销毁之后调用析构函数.
基本上第二个问题,即几个静态初始化变量的破坏的顺序如何,减少到这些初始化的顺序：
Dynamic initialization of a non-local variable with static storage@H_403_32@ duration is either ordered or unordered. Definitions of explicitly@H_403_32@ specialized class template static data members have ordered@H_403_32@ initialization. Other class template static data members (i.e.,@H_403_32@ implicitly or explicitly instantiated specializations) have unordered@H_403_32@ initialization. Other non-local variables with static storage@H_403_32@ duration have ordered initialization.
粗体句子包括所有静态初始化对象,这些对象不是实例化类的静态数据成员.它们在一个翻译单元内订购：
Variables with ordered initialization defined within a single@H_403_32@ translation unit shall be initialized in the order of their@H_403_32@ definitions in the translation unit.
所以,总结一下：
>静态初始化并且不是实例化类的静态数据成员的变量在翻译文件中以相反的定义顺序进行销毁.@H_403_32@> …任何动态初始化对象被破坏后,这些变量总是被破坏.
