PWB1/usr/man/man3/setjmp.3

.th SETJMP III 5/31/77
.sh NAME
setjmp, longjmp \*- execute non-local goto
.sh SYNOPSIS
.ft B
.br
int save[3];
.s3
setjmp(save)
.s3
longjmp(save)
.ft R
.sh DESCRIPTION
These routines are useful for dealing with errors 
and interrupts encountered in
a low-level subroutine of a program.
.s3
.it Setjmp
saves its stack environment
in
.it save
for
later use by
.it longjmp.
It returns 0 on the initial call.
.s3
.it Longjmp
restores the environment saved in
.it save
by
.it setjmp.
It then returns in such a way that execution
continues as if the call of 
.it setjmp
had just returned (with a nonzero value).
All accessible automatic and register data have values as of the
time 
.it setjmp
was called.
.s3
The routine that called
.it setjmp
must still be active when
.it longjmp
is called.
.s3
Although these functions are similar in purpose to
.it setexit
and
.it reset,
they permit several
.it setjmp
calls to be made,
each with a different
.it save.
.it Longjmp
may then return to any of them
by selecting the appropriate one.
.sh "SEE ALSO"
signal(II),
reset(III)