LONGJMP(3P) POSIX Programmer's Manual LONGJMP(3P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
NAME
longjmp -- non-local goto
SYNOPSIS
#include <setjmp.h>
void longjmp(jmp_buf env, int val);
DESCRIPTION
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.
The longjmp() function shall restore the environment saved by the most recent invocation of setjmp() in the same process, with the corre-
sponding jmp_buf argument. If the most recent invocation of setjmp() with the corresponding jmp_buf occurred in another thread, or if there
is no such invocation, or if the function containing the invocation of setjmp() has terminated execution in the interim, or if the invoca-
tion of setjmp() was within the scope of an identifier with variably modified type and execution has left that scope in the interim, the
behavior is undefined. It is unspecified whether longjmp() restores the signal mask, leaves the signal mask unchanged, or restores it to
its value at the time setjmp() was called.
All accessible objects have values, and all other components of the abstract machine have state (for example, floating-point status flags
and open files), as of the time longjmp() was called, except that the values of objects of automatic storage duration are unspecified if
they meet all the following conditions:
* They are local to the function containing the corresponding setjmp() invocation.
* They do not have volatile-qualified type.
* They are changed between the setjmp() invocation and longjmp() call.
As it bypasses the usual function call and return mechanisms, longjmp() shall execute correctly in contexts of interrupts, signals, and any
of their associated functions. However, if longjmp() is invoked from a nested signal handler (that is, from a function invoked as a result
of a signal raised during the handling of another signal), the behavior is undefined.
The effect of a call to longjmp() where initialization of the jmp_buf structure was not performed in the calling thread is undefined.
RETURN VALUE
After longjmp() is completed, program execution continues as if the corresponding invocation of setjmp() had just returned the value speci-
fied by val. The longjmp() function shall not cause setjmp() to return 0; if val is 0, setjmp() shall return 1.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
Applications whose behavior depends on the value of the signal mask should not use longjmp() and setjmp(), since their effect on the signal
mask is unspecified, but should instead use the siglongjmp() and sigsetjmp() functions (which can save and restore the signal mask under
application control).
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
setjmp(), sigaction(), siglongjmp(), sigsetjmp()
The Base Definitions volume of POSIX.1-2008, <setjmp.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Stan-
dard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE
/The Open Group 2013 LONGJMP(3P)