setjmp(3)

1SETJMP(3)                  Linux Programmer's Manual                 SETJMP(3)
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NAME

6       setjmp, sigsetjmp - save stack context for non-local goto
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SYNOPSIS

9       #include <setjmp.h>
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11       int setjmp(jmp_buf env);
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13       int sigsetjmp(sigjmp_buf env, int savesigs);
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       setjmp(): see NOTES.
18       sigsetjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE
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DESCRIPTION

21       setjmp()  and  longjmp(3) are useful for dealing with errors and inter‐
22       rupts encountered in a low-level subroutine  of  a  program.   setjmp()
23       saves the stack context/environment in env for later use by longjmp(3).
24       The stack context will be invalidated  if  the  function  which  called
25       setjmp() returns.
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27       sigsetjmp()  is similar to setjmp().  If, and only if, savesigs is non-
28       zero, the process's current signal mask is saved in  env  and  will  be
29       restored if a siglongjmp(3) is later performed with this env.
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RETURN VALUE

32       setjmp()  and  sigsetjmp() return 0 if returning directly, and non-zero
33       when returning from longjmp(3) or siglongjmp(3) using  the  saved  con‐
34       text.
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CONFORMING TO

37       C89,  C99,  and  POSIX.1-2001 specify setjmp().  POSIX.1-2001 specifies
38       sigsetjmp().
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NOTES

41       POSIX does not specify whether setjmp() will save the signal mask.   In
42       System  V  it  will  not.   In  4.3BSD it will, and there is a function
43       _setjmp that will not.  By default, Linux/glibc follows  the  System  V
44       behavior,  but  the BSD behavior is provided if the _BSD_SOURCE feature
45       test macro is  defined  and  none  of  _POSIX_SOURCE,  _POSIX_C_SOURCE,
46       _XOPEN_SOURCE,  _XOPEN_SOURCE_EXTENDED, _GNU_SOURCE, or _SVID_SOURCE is
47       defined.
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49       If you want to portably save and restore signal masks, use  sigsetjmp()
50       and siglongjmp().
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52       setjmp() and sigsetjmp() make programs hard to understand and maintain.
53       If possible an alternative should be used.
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COLOPHON

59       This page is part of release 3.22 of the Linux  man-pages  project.   A
60       description  of  the project, and information about reporting bugs, can
61       be found at http://www.kernel.org/doc/man-pages/.
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65                                  2009-06-26                         SETJMP(3)