std::nested_exception

STD：：嵌套[医]例外

Defined in header
class nested_exception;		(since C++11)

std::nested_exception是一个多态混合类，它可以捕获和存储当前的异常，从而可以在彼此之间嵌套任意类型的异常。

成员函数

(constructor)	constructs a nested_exception (public member function)
(destructor) virtual	destructs a nested exception (virtual public member function)
operator=	replaces the contents of a nested_exception (public member function)
rethrow_nested	throws the stored exception (public member function)
nested_ptr	obtains a pointer to the stored exception (public member function)

非会员职能

throw_with_nested (C++11)	throws its argument with std::nested_exception mixed in (function template)
rethrow_if_nested (C++11)	throws the exception from a std::nested_exception (function template)

例

演示通过嵌套异常对象进行的构造和递归。

二次

#include <iostream>
#include <stdexcept>
#include <exception>
#include <string>
#include <fstream>
 
// prints the explanatory string of an exception. If the exception is nested,
// recurses to print the explanatory of the exception it holds
void print_exception(const std::exception& e, int level =  0)
{
    std::cerr << std::string(level, ' ') << "exception: " << e.what() << '\n';
    try {
        std::rethrow_if_nested(e
    } catch(const std::exception& e) {
        print_exception(e, level+1
    } catch(...) {}
}
 
// sample function that catches an exception and wraps it in a nested exception
void open_file(const std::string& s)
{
    try {
        std::ifstream file(s
        file.exceptions(std::ios_base::failbit
    } catch(...) {
        std::throw_with_nested( std::runtime_error("Couldn't open " + s) 
    }
}
 
// sample function that catches an exception and wraps it in a nested exception
void run()
{
    try {
        open_file("nonexistent.file"
    } catch(...) {
        std::throw_with_nested( std::runtime_error("run() failed") 
    }
}
 
// runs the sample function above and prints the caught exception
int main()
{
    try {
        run(
    } catch(const std::exception& e) {
        print_exception(e
    }
}

二次

产出：

二次

exception: run() failed
 exception: Couldn't open nonexistent.file
  exception: basic_ios::clear

二次

另见

exception_ptr (C++11)	shared pointer type for handling exception objects (typedef)
throw_with_nested (C++11)	throws its argument with std::nested_exception mixed in (function template)
rethrow_if_nested (C++11)	throws the exception from a std::nested_exception (function template)

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