longjmp(3p) — Linux manual page

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
       corresponding 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.1‐2017 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
       corresponding 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 invocation 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.

       Although longjmp() is an async-signal-safe function, if it is
       invoked from a signal handler which interrupted a non-async-
       signal-safe function or equivalent (such as the processing
       equivalent to exit() performed after a return from the initial
       call to main()), the behavior of any subsequent call to a non-
       async-signal-safe function or equivalent 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 specified 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).

       It is recommended that applications do not call longjmp() or
       siglongjmp() from signal handlers. To avoid undefined behavior
       when calling these functions from a signal handler, the
       application needs to ensure one of the following two things:

        1. After the call to longjmp() or siglongjmp() the process only
           calls async-signal-safe functions and does not return from
           the initial call to main().

        2. Any signal whose handler calls longjmp() or siglongjmp() is
           blocked during every call to a non-async-signal-safe
           function, and no such calls are made after returning from the
           initial call to main().

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       setjmp(3p), sigaction(3p), siglongjmp(3p), sigsetjmp(3p)

       The Base Definitions volume of POSIX.1‐2017, setjmp.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/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               2017                       LONGJMP(3P)

Pages that refer to this page: setjmp.h(0p), exit(3p), ftw(3p), _longjmp(3p), setjmp(3p), sigaction(3p), siglongjmp(3p)

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