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.\" $FreeBSD: release/9.1.0/share/man/man9/KASSERT.9 206622 2010-04-14 19:08:06Z uqs $
.\"
.Dd January 14, 2000
.Dt KASSERT 9
.Os
.Sh NAME
.Nm KASSERT
.Nd kernel expression verification macro
.Sh SYNOPSIS
.Cd "options INVARIANTS"
.Pp
.In sys/param.h
.In sys/systm.h
.Fn KASSERT expression msg
.Sh DESCRIPTION
In a kernel compiled with
.Cd "options INVARIANTS" ,
the
.Fn KASSERT
macro tests the given
.Fa expression
and if it is false,
calls the
.Xr panic 9
function, terminating the running system.
.Pp
In a kernel that does not have
.Cd "options INVARIANTS" ,
the
.Fn KASSERT
macro is defined to be a no-op.
The
second argument is a
.Xr printf 9
format string and its arguments,
enclosed in parentheses.
.Sh EXAMPLES
The kernel function
.Fn vput
must not be called with a
.Dv NULL
pointer.
.Bd -literal -offset indent
void
vput(vp)
        struct vnode *vp;
{
	struct proc *p = curproc;
	KASSERT(vp != NULL, ("vput: null vp"));
	...
}
.Ed
.Sh SEE ALSO
.Xr config 8 ,
.Xr panic 9
.Sh AUTHORS
This manual page was written by
.An Jonathan M. Bresler
.Aq jmb@FreeBSD.org .