std::nested_exception (3) - Linux Manuals

std::nested_exception: std::nested_exception

NAME

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