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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 program.  longjmp() restores the environment saved by  the  last
       call of setjmp(3) with the corresponding env argument.  After longjmp() is completed, pro-
       gram 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 sec-
       ond 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, sig-
       longjmp() 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(3) 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 3.53 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)

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