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std::nested_exception

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< cpp‎ | error
Revision as of 03:02, 3 June 2013 by P12 (Talk | contribs)

 
 
 
 
Defined in header <exception>
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

constructs a nested_exception
(public member function)
[virtual]
destructs a nested exception
(virtual public member function)
replaces the contents of a nested_exception
(public member function)
throws the stored exception
(public member function)
obtains a pointer to the stored exception
(public member function)

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

See also

shared pointer type for handling exception objects
(typedef) [edit]
throws its argument with std::nested_exception mixed in
(function template) [edit]
throws the exception from a std::nested_exception
(function template) [edit]