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)