Defined in header <csetjmp>
             void longjmp( std::jmp_buf env, int status );
(until C++17)
[[noreturn]] void longjmp( std::jmp_buf env, int status );
(since C++17)

Loads the execution context env saved by a previous call to setjmp. This function does not return. Control is transferred to the call site of the macro setjmp that set up env. That setjmp then returns the value, passed as the status.

If the function that called setjmp has exited, the behavior is undefined (in other words, only long jumps up the call stack are allowed).

Extra restrictions in C++

On top of C longjmp, C++ std::longjmp has more restricted behavior.

If replacing std::longjmp with throw and setjmp with catch would invoke a non-trivial destructor for any automatic object, the behavior of such std::longjmp is undefined.

The behavior is undefined if std::longjmp is called in a coroutine in a place where the co_await operator may be used.

(since C++20)


env - variable referring to the execution state of the program saved by setjmp
status - the value to return from setjmp. If it is equal to ​0​, 1 is used instead

Return value



std::longjmp is the mechanism used in C to handle unexpected error conditions where the function cannot return meaningfully. C++ generally uses exception handling for this purpose.


#include <csetjmp>
#include <iostream>
std::jmp_buf my_jump_buffer;
[[noreturn]] void foo(int status) 
    std::cout << "foo(" << status << ") called\n";
    std::longjmp(my_jump_buffer, status + 1); // setjmp() will return status + 1
int main()
    volatile int count = 0; // modified locals in setjmp scope must be volatile
    if (setjmp(my_jump_buffer) != 5) // equality against constant expression in an if
        count += 1; // Increment of a volatile variable is deprecated since C++20 (P1152)
        foo(count); // This will cause setjmp() to exit


foo(1) called
foo(2) called
foo(3) called
foo(4) called

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 619 C++98 the wording of the extra restrictions in C++ was vague improved the wording
LWG 894 C++98 the behavior was undefined if replacing
std::longjmp with throw and setjmp with
catch would destroy any automatic object
the behavior is only undefined
if a non-trivial destructor for
any automatic object is invoked

See also

saves the context
(function macro)
C documentation for longjmp

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