std::exception_ptr

 

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

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

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, enumeration, or pointer type. It is convertible to bool.

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.

Example

#include <iostream>
#include <string>
#include <exception>
#include <stdexcept>
 
void handle_eptr(std::exception_ptr eptr) // passing by value is ok
{
    try {
        if (eptr != std::exception_ptr()) {
            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"

See also

make_exception_ptr (C++11)	creates an std::exception_ptr from an exception object (function template)
current_exception (C++11)	captures the current exception in a std::exception_ptr (function)
rethrow_exception (C++11)	throws the exception from an std::exception_ptr (function)