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

NAME
     std::rethrow_exception - std::rethrow_exception

Synopsis
	Defined in header <exception>
	[[noreturn]]  void  rethrow_exception(	std::exception_ptr  p );  (since
     C++11)

	Throws the previously captured exception object referred-to by	the  ex-
     ception pointer
	p, or a copy of that object.

	It is unspecified whether a copy is made. If a copy is made, the storage
     for it is
	allocated in an unspecified way.

	The behavior is undefined if p is null.

Parameters
	p - non-null std::exception_ptr

Return value
	(none)

Exceptions
	The exception object referred-to by p if no copy is made.

	Otherwise,  a  copy  of such exception object if the implementation suc-
     cessfully copied
	the exception object.

	Otherwise, std::bad_alloc or the exception thrown when copying	the  ex-
     ception object,
	if allocation or copying fails, respectively.

Notes
	Before	P1675R2, rethrow_exception was not allowed to copy the exception
     object,
	which is unimplementable on some platforms where exception  objects  are
     allocated on
	the stack.

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
	exception_ptr	  shared pointer type for handling exception objects
	(C++11) 	  (typedef)
	current_exception captures the current exception in a std::exception_ptr
	(C++11) 	  (function)

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