_longjmp - Man Page

non-local goto


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#include <setjmp.h>

void _longjmp(jmp_buf env, int val);
int _setjmp(jmp_buf env);


The _longjmp() and _setjmp() functions shall be equivalent to longjmp() and setjmp(), respectively, with the additional restriction that _longjmp() and _setjmp() shall not manipulate the signal mask.

If _longjmp() is called even though env was never initialized by a call to _setjmp(), or when the last such call was in a function that has since returned, the results are undefined.

Return Value

Refer to longjmp() and setjmp().


No errors are defined.

The following sections are informative.



Application Usage

If _longjmp() is executed and the environment in which _setjmp() was executed no longer exists, errors can occur. The conditions under which the environment of the _setjmp() no longer exists include exiting the function that contains the _setjmp() call, and exiting an inner block with temporary storage. This condition might not be detectable, in which case the _longjmp() occurs and, if the environment no longer exists, the contents of the temporary storage of an inner block are unpredictable. This condition might also cause unexpected process termination. If the function has returned, the results are undefined.

Passing longjmp() a pointer to a buffer not created by setjmp(), passing _longjmp() a pointer to a buffer not created by _setjmp(), passing siglongjmp() a pointer to a buffer not created by sigsetjmp(), or passing any of these three functions a buffer that has been modified by the user can cause all the problems listed above, and more.

The _longjmp() and _setjmp() functions are included to support programs written to historical system interfaces. New applications should use siglongjmp() and sigsetjmp() respectively.



Future Directions

The _longjmp() and _setjmp() functions may be removed in a future version.

See Also

longjmp(), setjmp(), siglongjmp(), sigsetjmp()

The Base Definitions volume of POSIX.1-2017, <setjmp.h>

Referenced By

setjmp.h(0p), sigaction(3p).

2017 IEEE/The Open Group POSIX Programmer's Manual