# std::current_exception

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Defined in header `<exception>` |  |
std::exception_ptr current_exception() noexcept; |  | (since C++11) (constexpr since C++26)

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.

This function can be called in a std::terminate_handler to retrieve the exception which has provoked the invocation of std::terminate.

### 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.

### 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 previously-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;
            }
        }
    }

Feature-test macro | Value | Std | Feature
--- | --- | --- | ---
`__cpp_lib_constexpr_exceptions` | `202411L` | (C++26) | constexpr for exception types

### 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
        {
            [[maybe_unused]]
            char ch = 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 (C++11) | shared pointer type for handling exception objects (typedef)
rethrow_exception (C++11) | throws the exception from an std::exception_ptr (function)
make_exception_ptr (C++11) | creates an std::exception_ptr from an exception object (function template)
uncaught_exceptionuncaught_exceptions (removed in C++20*)(C++17) | checks if exception handling is currently in progress (function)

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