std::current_exception (3) - Linux Manuals

std::current_exception: std::current_exception

NAME

std::current_exception - std::current_exception

Synopsis

Defined in header <exception>
std::exception_ptr current_exception() noexcept; (since C++11)

If called during exception handling (typically, in a catch clause), captures the current exception object and creates an std::exception_ptr that holds either a copy or a reference to that exception object (depending on the implementation). The referenced object remains valid at least as long as there is an exception_ptr object that refers to it.
If the implementation of this function requires a call to new and the call fails, the returned pointer will hold a reference to an instance of std::bad_alloc.
If the implementation of this function requires copying the captured exception object and its copy constructor throws an exception, the returned pointer will hold a reference to the exception thrown. If the copy constructor of the thrown exception object also throws, the returned pointer may hold a reference to an instance of std::bad_exception to break the endless loop.
If the function is called when no exception is being handled, an empty std::exception_ptr is returned.

Parameters

(none)

Return value

An instance of std::exception_ptr holding a reference to the exception object, or a copy of the exception object, or to an instance of std::bad_alloc or to an instance of std::bad_exception.

Example

// Run this code

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

  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 an 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 destructed

Output:

  Caught exception "basic_string::at"