date and time created 93/05/24 10:58:50 by bostic

[unix-history] / usr / src / lib / libc / gen / setjmp.3

.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)setjmp.3	6.10 (Berkeley) %G%
.\"
.Dd 
.Dt SETJMP 3
.Os BSD 4
.Sh NAME
.Nm sigsetjmp ,
.Nm siglongjmp ,
.Nm setjmp ,
.Nm longjmp ,
.Nm _setjmp ,
.Nm _longjmp longjmperror
.Nd non-local jumps
.Sh SYNOPSIS
.Fd #include <setjmp.h>
.Ft int
.Fn sigsetjmp "sigjmp_buf env" "int savemask"
.Ft void
.Fn siglongjmp "sigjmp_buf env" "int val"
.Ft int
.Fn setjmp "jmp_buf env"
.Ft void
.Fn longjmp "jmp_buf env" "int val"
.Ft int
.Fn _setjmp "jmp_buf env"
.Ft void
.Fn _longjmp "jmp_buf env" "int val"
.Ft void
.Fn longjmperror void
.Sh DESCRIPTION
The
.Fn sigsetjmp ,
.Fn setjmp ,
and
.Fn _setjmp
functions save their calling environment in
.Fa env .
Each of these functions returns 0.
.Pp
The corresponding
.Fn longjmp
functions restore the environment saved by their most recent respective
invocations
of the
.Fn setjmp
function.
They then return so that program execution continues as if the corresponding
invocation of the
.Fn setjmp
call had just returned  the value specified by
.Fa val ,
instead of 0.
.Pp
Pairs of calls may be intermixed, i.e. both
.Fn sigsetjmp
and
.Fn siglongjmp
and
.Fn setjmp
and
.Fn longjmp
combinations may be used in the same program, however, individual
calls may not, e.g. the
.Fa env
argument to
.Fn setjmp
may not be passed to
.Fn siglongjmp .
.Pp
The
.Fn longjmp
routines may not be called after the routine which called the
.Fn setjmp
routines returns.
.Pp
All accessible objects have values as of the time
.Fn longjmp
routine was called, except that the values of objects of automatic storage
invocation duration that do not have the
.Em volatile
type and have been changed between the
.Fn setjmp
invocation and
.Fn longjmp
call are indeterminate.
.Pp
The
.Fn setjmp Ns / Ns Fn longjmp
pairs save and restore the signal mask while
.Fn _setjmp Ns / Ns Fn _longjmp
pairs save and restore only the register set and the stack.
(See
.Fn sigmask 2 . )
.Pp
The
.Fn sigsetjmp Ns / Ns Fn siglongjmp
function
pairs save and restore the signal mask if the argument
.Fa savemask
is non-zero, otherwise only the register set and the stack are saved.
.Sh ERRORS
If the contents of the
.Fa env
are corrupted, or correspond to an environment that has already returned,
the
.Fn longjmp
routine calls the routine
.Fn longjmperror 3 .
If
.Fn longjmperror
returns the program is aborted (see
.Xr abort 2 ) .
The default version of
.Fn longjmperror
prints the message
.Dq Li longjmp botch
to standard error and returns.
User programs wishing to exit more gracefully should write their own
versions of
.Fn longjmperror .
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr sigaltstack 2 ,
.Xr signal 3
.Sh STANDARDS
The
.Fn setjmp
and
.Fn longjmp
functions conform to
.St -ansiC .
The
.Fn sigsetjmp
and
.Fn siglongjmp
functions conform to
.St -p1003.1-88 .