c – 构造函数初始化列表中的执行顺序

构造函数初始化列表中的执行顺序是否可确定？我知道成员中的成员顺序是这些成员初始化的顺序,但如果我有这样的场景：

class X()
{
X_Implementation* impl_;
};  

and then providing that allocator is available:

X::X():impl_(Allocate(sizeof(X_Implementation)))//HERE I'M ALLOCATING <--1
,impl_(Construct<X_Implementation>(impl_))//AND HERE I'M CONSTRUCTING <--2
{
}

但为了使这个可靠,这个顺序必须是从左到右.是否保留了高级书籍std ::或者没有？如果不是,我总是可以将第二条线移动到身体中.

解决方法:

根据ISO / IEC 14882：2003(E)第12.6.2节：

Initialization shall proceed in the following order:

• First, and only for the constructor of the most derived class as described below, virtual base classes shall
  be initialized in the order they appear on a depth-first left-to-right traversal of the directed acyclic graph
  of base classes, where “left-to-right” is the order of appearance of the base class names in the derived
  class base-specifier-list.
  
• Then, direct base classes shall be initialized in declaration order as they appear in the base-specifier-list
  (regardless of the order of the mem-initializers).
• Then, nonstatic data members shall be initialized in the order they were declared in the class definition
  (again regardless of the order of the mem-initializers).
• Finally, the body of the constructor is executed.

因此,按照该顺序,您将获得订单.同样根据标准,订单被如此规定,使得对象可以以完全相反的顺序未初始化.

标签：c,operator-precedence
来源： https://codeday.me/bug/20190918/1810907.html