longjmp never returns Post: 302088234

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longjmp

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,  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 3.27 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)