c – 构造函数完全包含什么内容？

根据C标准,类构造函数的noexcept noexcept-spec究竟适用于什么？

>功能体？

>在可选的ctor-initializer中初始化成员？

>在可选的mem初始化器中初始化基类？
>在可选的mem初始化器中初始化类成员？

>复合语句？
> function-try-block？

>在ctor-initializer中未初始化对象基类的初始化？
>初始化对象类成员未初始化在ctor-initializer？
还有一些额外的东西

换句话说,如果noexcept(true)抛出异常,则noexcept noexcept-specification(即触发std :: terminate())包含以上哪一个？

请提供参考标准.也欢迎任何使用noexcept构造函数的提示.谢谢！

解决方法

In other words,which of the above are encompassed by the noexcept noexcept-specification…?

异常规范(noexcept和动态异常规范)涉及构建基础类,构件和初始化成员以及构造函数体中的代码.基本上,在构造对象中执行的所有功能 – 这是有道理的,因为异常规范与对象的构造函数相关联,因此它应该涵盖在构造对象期间执行的代码;如果建筑的任何部分没有涵盖,这将是违反直觉的.

支持标准报价…

如果在施工期间抛出异常(可能未处理)怎么办？

[except.spec]/9

Whenever an exception of type E is thrown and the search for a handler ([except.handle]) encounters the outermost block of a function with an exception specification that does not allow E,then,

if the function deFinition has a dynamic-exception-specification,the function std::unexpected() is called ([except.unexpected]),

otherwise,the function std::terminate() is called ([except.terminate]).

“功能的最外面的块”是什么意思？功能的身体1

上述exception specification包括noexcept规范.

如何在隐式声明的构造函数中确定隐式声明的异常规范？

[except.spec]/15

An implicitly-declared special member function f of some class X is considered to have an implicit exception specification that consists of all the members from the following sets:

if f is a constructor,

the sets of potential exceptions of the constructor invocations

for X‘s non-variant non-static data members,

for X‘s direct base classes,and

if X is non-abstract ([class.abstract]),for X‘s virtual base classes,

(including default argument expressions used in such invocations) as selected by overload resolution for the implicit deFinition of f ([class.ctor])…

the sets of potential exceptions of the initialization of non-static data members from brace-or-equal-initializers that are not ignored ([class.base.init]);

这对编译器将用来确定(因此考虑覆盖)异常规范提供了非常有用的澄清.

1“功能的最外面的块”是什么意思？有人对对功能块的定义的关注发表了评论.该标准没有对函数块的正式定义.功能的短语块仅在Exception Handling [except]中使用.该短语从C 98开始就包含在标准中.

为了进一步明确,我们需要寻求替代来源并得出一些合理的结论.

从Stroustrup C++ glossary;

function body – the outermost block of a function. See also: try-block,function deFinition. TC++PL 2.7,13.

从[dcl.fct.def.general]/1起,使用复合语句和function-try-block覆盖ctor-initializer的函数体的语法;

Function deFinitions have the form;

…

function-body:
ctor-initializer_opt compound-statement
function-try-block

…

Any informal reference to the body of a function should be interpreted as a reference to the non-terminal function-body…

同样重要的是要记住,异常规范与功能相关,而不是一般的代码块(作用域等).

给定异常处理子句和Stroustrup FAQ中的短语的年龄,函数的块与函数体相同,标准可能对异常子句中使用的语言进行更新.

给出以下代码的一些实证证据,用于构建a1,a2和a3(当其他人被注释掉)时,会导致std :: terminate被调用.结果适用于g++,clang和MSVC.

struct Thrower { Thrower() { std::cout << "throwing..." << std::endl; throw 42; } };

struct AsMember { Thrower t_; AsMember() noexcept : t_{} { std::cout << "ctor" << std::endl; } };

struct AsBase : Thrower { AsBase() noexcept { std::cout << "ctor" << std::endl; } };

struct AsNSDMI { Thrower t_ {}; AsNSDMI() noexcept { std::cout << "ctor" << std::endl; } };

int main()
{
    std::set_terminate([](){ std::cout << "terminating..." << std::endl; });
    try {
        //AsMember a1{};
        //AsBase a2{};
        AsNSDMI a3{};
    }
    catch (...) { std::cout << "caught..." << std::endl; }
    return 0;
}

c – 构造函数完全包含什么内容？

解决方法

相关文章