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

NAME
     std::exception_ptr - std::exception_ptr

Synopsis
	Defined in header <exception>
	typedef /*unspecified*/ exception_ptr;	(since C++11)

	std::exception_ptr  is	a nullable pointer-like type that manages an ex-
     ception object
	which has been thrown and captured with std::current_exception.  An  in-
     stance of
	std::exception_ptr  may  be  passed to another function, possibly on an-
     other thread,
	where the exception may be rethrown and handled with a catch clause.

	A default-constructed std::exception_ptr is a null pointer; it does  not
     point to an
	exception object.

	Two  instances of std::exception_ptr compare equal only if they are both
     null or both
	point at the same exception object.

	std::exception_ptr is not implicitly convertible to any arithmetic, enu-
     meration, or
	pointer type. It is contextually convertible to bool, and will	evaluate
     to false if
	it is null, true otherwise.

	The  exception	object referenced by an std::exception_ptr remains valid
     as long as
	there remains at least one std::exception_ptr that is referencing it:
	std::exception_ptr is a shared-ownership smart pointer (note: this is in
     addition to
	the usual exception object lifetime rules).

	std::exception_ptr meets the requirements of NullablePointer.

Example
     // Run this code

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

      void handle_eptr(std::exception_ptr eptr) // passing by value is ok
      {
	  try
	  {
	      if (eptr)
		  std::rethrow_exception(eptr);
	  }
	  catch(const std::exception& e)
	  {
	      std::cout << "Caught exception: '" << e.what() << "'\n";
	  }
      }

      int main()
      {
	  std::exception_ptr eptr;

	  try
	  {
	      std::string().at(1); // this generates a std::out_of_range
	  }
	  catch(...)
	  {
	      eptr = std::current_exception(); // capture
	  }

	  handle_eptr(eptr);

      } // destructor for std::out_of_range called here, when the  eptr  is  de-
     structed

Possible output:
      Caught  exception:  'basic_string::at:  __n  (which  is 1) >= this->size()
     (which is 0)'

See also
	make_exception_ptr creates an std::exception_ptr from an  exception  ob-
     ject
	(C++11) 	   (function template)
	current_exception   captures  the  current  exception  in  a std::excep-
     tion_ptr
	(C++11) 	   (function)
	rethrow_exception  throws the exception from an std::exception_ptr
	(C++11) 	   (function)

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