SETJMP(3) | Library Functions Manual | SETJMP(3) |
sigsetjmp
, siglongjmp
,
setjmp
, longjmp
,
_setjmp
, _longjmp
,
longjmperror
—
#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);
sigsetjmp
(), setjmp
(), and
_setjmp
() functions save their calling environment in
env. Each of these functions returns 0.
The corresponding longjmp
() functions
restore the environment saved by the most recent invocation of the
respective 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
()
as well as 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 storage invocation duration that do not have the
volatile
type and have been changed between the
setjmp
() invocation and
longjmp
() call are indeterminate.
The
setjmp
()/longjmp
() function
pairs save and restore the signal mask while
_setjmp
()/_longjmp
()
function pairs save and restore only the register 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.
In other words,
setjmp
()/longjmp
() are
functionally equivalent to
sigsetjmp
()/siglongjmp
()
when sigsetjmp
() is called with a non-zero
savemask argument. Conversely,
_setjmp
()/_longjmp
() are
functionally equivalent to
sigsetjmp
()/siglongjmp
()
when sigsetjmp
() is called with a zero-value
savemask.
The
sigsetjmp
()/siglongjmp
()
interfaces are preferred for maximum portability.
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 programs wishing to exit more gracefully should write their own
versions of longjmperror
().
setjmp
() and longjmp
()
functions conform to ANSI X3.159-1989
(“ANSI C89”). The
sigsetjmp
() and siglongjmp
()
functions conform to IEEE Std 1003.1-1990
(“POSIX.1”).
setjmp
()/longjmp
() functions
have been equivalent to the BSD
_setjmp
()/_longjmp
() functions
and do not restore the signal mask. Because of this discrepancy, the
sigsetjmp
()/siglongjmp
()
interfaces should be used if portability is desired.
Use of longjmp
() or
siglongjmp
() from inside a signal handler is not as
easy as it might seem. Generally speaking, all possible code paths between
the setjmp
() and longjmp
()
must be signal race safe. Furthermore, the code paths must not do resource
management (such as open(2) or
close(2)) without blocking the
signal in question, or resources might be mismanaged. Obviously this makes
longjmp
() much less useful than previously
thought.
June 1, 2008 | NetBSD 9.0 |