man3/setjmp.3

   1 .\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
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  23 .\" Added sigsetjmp, Sun Mar  2 22:03:05 EST 1997, jrv@vanzandt.mv.com
  24 .\" Modifications, Sun Feb 26 14:39:45 1995, faith@cs.unc.edu
  25 .\" "
  26 .TH SETJMP 3 1997-03-02 "" "Library functions"
  27 .SH NAME
  28 setjmp, sigsetjmp \- save stack context for non-local goto
  29 .SH SYNOPSIS
  30 .ad l
  31 .B #include <setjmp.h>
  32 .sp
  33 .nf
  34 .BI "int setjmp(jmp_buf " env );
  35 .BI "int sigsetjmp(sigjmp_buf " env ", int " savesigs );
  36 .fi
  37 .ad b
  38 .SH DESCRIPTION
  39 \fBsetjmp()\fP and \fBlongjmp()\fP are useful for dealing with errors
  40 and interrupts encountered in a low-level subroutine of a program.
  41 \fBsetjmp()\fP saves the stack context/environment in \fIenv\fP for
  42 later use by \fBlongjmp()\fP.  The stack context will be invalidated
  43 if the function which called \fBsetjmp()\fP returns.
  44 .P
  45 \fBsigsetjmp()\fP is similar to \fBsetjmp()\fP.  If \fIsavesigs\fP is nonzero,
  46 the set of blocked signals is saved in \fIenv\fP and will be restored
  47 if a \fBsiglongjmp()\fP is later performed with this \fIenv\fP.
  48 .SH "RETURN VALUE"
  49 \fBsetjmp()\fP and \fBsigsetjmp()\fP return 0 if returning directly, and
  50 non-zero when returning from \fBlongjmp()\fP using the saved context.
  51 .SH "CONFORMING TO"
  52 POSIX, ISO 9899 (C99)
  53 .SH NOTES
  54 POSIX does not specify whether \fBsetjmp\fP will save the
  55 signal context. (In SYSV it will not. In BSD4.3 it will, and there
  56 is a function \fB_setjmp\fP that will not.)
  57 If you want to save signal masks, use \fBsigsetjmp\fP.
  58 .P
  59 \fBsetjmp()\fP and \fBsigsetjmp\fP make programs hard to understand
  60 and maintain.  If possible an alternative should be used.
  61 .SH "SEE ALSO"
  62 .BR longjmp (3),
  63 .BR siglongjmp (3)