std::nested_exception (3) Linux Manual Page

std::nested_exception – std::nested_exception

Synopsis

Defined in header <exception>
class nested_exception; (since C++11)
std::nested_exception is a polymorphic mixin class which can capture and store the current exception, making it possible to nest exceptions of arbitrary types within each other.

Member functions

               constructs a nested_exception
constructor (public member function)

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

Non-member functions

throw_with_nested throws its argument with std::nested_exception mixed in
                  (function template)
(C++11)

rethrow_if_nested throws the exception from a std::nested_exception
                  (function template)
(C++11)

Example

Demonstrates construction and recursion through a nested exception object
// Run this code

#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);
    }
}

Output:

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

See also

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