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LONGJMP(3)                 Linux Programmer's Manual                LONGJMP(3)



NAME
       longjmp, siglongjmp - non-local jump to a saved stack context

SYNOPSIS
       #include <setjmp.h>

       void longjmp(jmp_buf env, int val);

       void siglongjmp(sigjmp_buf env, int val);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       siglongjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE

DESCRIPTION
       longjmp() and setjmp(3) are useful for dealing with errors and interrupts encountered in a low-level subroutine
       of a program.  longjmp() restores the environment saved by the last call of setjmp(3)  with  the  corresponding
       env  argument.   After  longjmp()  is  completed,  program  execution continues as if the corresponding call of
       setjmp(3) had just returned the value val.  longjmp() cannot cause 0 to be returned.  If longjmp()  is  invoked
       with a second argument of 0, 1 will be returned instead.

       siglongjmp()  is  similar  to  longjmp()  except  for  the  type  of  its  env  argument.  If, and only if, the
       sigsetjmp(3) call that set this env used a non-zero savesigs flag, siglongjmp() also restores the  signal  mask
       that was saved by sigsetjmp(3).

RETURN VALUE
       These functions never return.

CONFORMING TO
       C89, C99, and POSIX.1-2001 specify longjmp().  POSIX.1-2001 specifies siglongjmp().

NOTES
       POSIX does not specify whether longjmp() will restore the signal context (see setjmp(3) for some more details).
       If you want to portably save and restore signal masks, use sigsetjmp() and siglongjmp().

       The values of automatic variables are unspecified after a call to longjmp() if they meet all the following cri-
       teria:

       ?  they are local to the function that made the corresponding setjmp(3) call;

       ?  their values are changed between the calls to setjmp(3) and longjmp(); and

       ?  they are not declared as volatile.

       Analogous remarks apply for siglongjmp().

       longjmp() and siglongjmp() make programs hard to understand and maintain.  If possible an alternative should be
       used.

SEE ALSO
       setjmp(3), sigsetjmp(3)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2009-01-13                        LONGJMP(3)