std::nested_exception

Defined in header <exception>

1	`class` `nested_exception;`

(since C++11)

std::nested_exceptions 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

(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)

Non-member functions

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)

Example

Demonstrates construction and recursion through a nested exception object.

#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

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)

std::nested_exception

Member functions

Non-member functions

Example

See also