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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                                                   2015-08-08                                         LONGJMP(3)