setjmp(3)

NAME

sigsetjmp, siglongjmp, setjmp, longjmp, _setjmp, _longjmp,

longjmperror non-local jumps

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <setjmp.h>
int
sigsetjmp(sigjmp_buf env, int savemask);
void
siglongjmp(sigjmp_buf env, int val);
int
setjmp(jmp_buf env);
void
longjmp(jmp_buf env, int val);
int
_setjmp(jmp_buf env);
void
_longjmp(jmp_buf env, int val);
void
longjmperror(void);

DESCRIPTION

The sigsetjmp(), setjmp(), and _setjmp() functions save

their calling
environment in env. Each of these functions returns 0.

The corresponding longjmp() functions restore the environ

ment saved by
their most recent respective invocations of the setjmp()

function. They
then return so that program execution continues as if the

corresponding
invocation of the setjmp() call had just returned the value

specified by
val, instead of 0.

Pairs of calls may be intermixed, i.e., both sigsetjmp() and

siglongjmp()
and setjmp() and longjmp() combinations may be used in the

same program,
however, individual calls may not, e.g. the env argument to

setjmp() may
not be passed to siglongjmp().

The longjmp() routines may not be called after the routine

which called
the setjmp() routines returns.

All accessible objects have values as of the time longjmp()

routine was
called, except that the values of objects of automatic stor

age invocation
duration that do not have the volatile type and have been

changed between
the setjmp() invocation and longjmp() call are indetermi

nate.

The setjmp()/longjmp() pairs save and restore the signal

mask while
_setjmp()/_longjmp() pairs save and restore only the regis

ter set and the
stack. (See sigprocmask(2).)

The sigsetjmp()/siglongjmp() function pairs save and restore

the signal
mask if the argument savemask is non-zero, otherwise only

the register
set and the stack are saved.

ERRORS

If the contents of the env are corrupted, or correspond to

an environment
that has already returned, the longjmp() routine calls the

routine
longjmperror(3). If longjmperror() returns the program is

aborted (see
abort(3)). The default version of longjmperror() prints the

message
``longjmp botch'' to standard error and returns. User pro

grams wishing
to exit more gracefully should write their own versions of
longjmperror().

SEE ALSO

sigaction(2), sigaltstack(2), signal(3)

STANDARDS

The setjmp() and longjmp() functions conform to ISO/IEC

9899:1990
(``ISO C89''). The sigsetjmp() and siglongjmp() functions

conform to
IEEE Std 1003.1-1988 (``POSIX.1'').

BSD June 4, 1993

BSD