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std::current_exception(3) C++ Standard Libary std::current_exception(3) 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 implemen- tation). The referenced object remains valid at least as long as there is an ex- ception_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. This function can be called in a std::terminate_handler to retrieve the exception which has provoked the invocation of std::terminate. Parameters (none) Return value An instance of std::exception_ptr holding a reference to the excep- tion object, or a copy of the exception object, or to an instance of std::bad_alloc or to an instance of std::bad_exception. Notes On the implementations that follow Itanium C++ ABI (GCC, Clang, etc), exceptions are allocated on the heap when thrown (except for std::bad_alloc in some cases), and this function simply creates the smart pointer referencing the pre- viously-allocated object, On MSVC, exceptions are allocated on stack when thrown, and this function performs the heap allocation and copies the exception object. On Windows in managed CLR environments [1], the implementation will store a std::bad_exception when the current exception is a managed exception ([2]). Note that catch(...) catches also managed exceptions: #include <exception> int main() { try { throw gcnew System::Exception("Managed exception"); } catch (...) { std::exception_ptr ex = std::current_exception(); try { std::rethrow_exception(ex); } catch (std::bad_exception const &) { // This will be printed. std::cout << "Bad exception" << std::endl; } } } 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 destructed 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 ob- jects (C++11) (typedef) rethrow_exception throws the exception from an std::exception_ptr (C++11) (function) make_exception_ptr creates an std::exception_ptr from an exception object (C++11) (function template) uncaught_exception uncaught_exceptions checks if exception handling is currently in progress (removed in C++20) (function) (C++17) http://cppreference.com 2024.06.10 std::current_exception(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Possible output: | See also
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