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,
       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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────┬───────────────┬─────────┐
       │Interface               │ Attribute     │ Value   │
       ├────────────────────────┼───────────────┼─────────┤
       │longjmp(), siglongjmp() │ Thread safety │ MT-Safe │
       └────────────────────────┴───────────────┴─────────┘

CONFORMING TO

       longjmp(): POSIX.1-2001, POSIX.1-2008, C89, C99.

       siglongjmp(): POSIX.1-2001, POSIX.1-2008.

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:

       •  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

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       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.

                                            2015-08-08                                 LONGJMP(3)