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



NAME
       longjmp, siglongjmp - nonlocal 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 pro-
       gram.  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  nonzero  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 criteria:

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

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

       o  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 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                                           2009-01-13                                                 LONGJMP(3)