std::exception_ptr

C++

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Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Utilities library

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Library feature-test macros
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
integer_sequence (C++14)
Relational operators (deprecated)
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
Elementary string conversions
to_chars (C++17)
from_chars (C++17)
chars_format (C++17)
Type operations
declval (C++11)
as_const (C++17)

Error handling

Exception handling exception uncaught_exceptionuncaught_exceptions (C++17) exception_ptr (C++11) make_exception_ptr (C++11) current_exception (C++11) rethrow_exception (C++11) nested_exception (C++11) throw_with_nested (C++11) rethrow_if_nested (C++11) Exception handling failures terminate terminate_handler get_terminate (C++11) set_terminate bad_exception unexpected (until C++17) unexpected_handler (until C++17) get_unexpected (C++11)(until C++17) set_unexpected (until C++17) Contracts contract_violation (C++20)

Exception categories logic_error invalid_argument domain_error length_error out_of_range runtime_error range_error overflow_error underflow_error tx_exception (TM TS) Error codes Error codes errno Assertions assert system_error facility error_category (C++11) generic_category (C++11) system_category (C++11) error_condition (C++11) errc (C++11) error_code (C++11) system_error (C++11)

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.

A 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 contextually convertible to bool, and will evaluate to false if it is null, true otherwise.

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 (note; this is in addition to the usual exception object lifetime rules)

std::exception_ptr meets the requirements of NullablePointer.

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"

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)