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std::nested_exception(3)       C++ Standard Libary	std::nested_exception(3)

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
	constructor    constructs a nested_exception
		       (public member function)
	destructor     destructs a nested exception
	[virtual]      (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 throws its argument with  std::nested_exception  mixed
     in
	(C++11) 	  (function template)
	rethrow_if_nested throws the exception from a std::nested_exception
	(C++11) 	  (function template)

Example
	Demonstrates  construction  and recursion through a nested exception ob-
     ject.

     // Run this code

      #include <exception>
      #include <fstream>
      #include <iostream>
      #include <stdexcept>
      #include <string>

      // 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& nestedException)
	  {
	      print_exception(nestedException, level + 1);
	  }
	  catch (...) {}
      }

      // sample function that catches an exception and wraps it in a nested  ex-
     ception
      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 ex-
     ception
      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);
	  }
      }

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

http://cppreference.com 	   2024.06.10		std::nested_exception(3)
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