.\"     $NetBSD: KASSERT.9,v 1.13 2011/09/27 00:36:51 jym Exp $
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.\" Copyright (c) 2006 Igor Sobrado
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.Dd September 27, 2011
.Dt KASSERT 9
.Os
.Sh NAME
.Nm KASSERT ,
.Nm KASSERTMSG ,
.Nm KDASSERT ,
.Nm KDASSERTMSG
.Nd kernel expression verification macros
.Sh SYNOPSIS
.Ft void
.Fn KASSERT expression
.Ft void
.Fn KASSERTMSG expression format ...
.Ft void
.Fn KDASSERT expression
.Ft void
.Fn KDASSERTMSG expression format ...
.Sh DESCRIPTION
These machine independent assertion-checking macros cause a kernel
.Xr panic 9
if the given
.Ar expression
evaluates to false.
Two compile-time
.Xr options 4
define the behavior of the checks.
.Bl -enum -offset 2n
.It
The
.Fn KASSERT
and
.Fn KASSERTMSG
tests are included only in kernels compiled with the
.Dv DIAGNOSTIC
configuration option.
In a kernel that does not have this configuration option,
the macros are defined to be no-ops.
.It
The
.Fn KDASSERT
and
.Fn KDASSERTMSG
tests are included only in kernels compiled with the
.Dv DEBUG
configuration option.
The
.Fn KDASSERT
and
.Fn KASSERT
macros are identical except for the controlling option
.Pf ( Dv DEBUG
vs
.Dv DIAGNOSTIC ) .
Basically,
.Fn KASSERT
should be used for light-weight checks and
.Fn KDASSERT
should be used for heavier ones.
.El
.Pp
Callers should not rely on the side effects of
.Ar expression
because, depending on the kernel compile options mentioned above,
.Ar expression
might not be evaluated at all.
.Pp
The panic message will display the style of assertion (debugging
vs. diagnostic), the expression that failed and the filename, and line
number the failure happened on.
The
.Fn KASSERTMSG
and
.Fn KDASSERTMSG
macros append
to the
.Xr panic 9
format string the message specified by
.Fa format
and its subsequent arguments, similar to
.Xr printf 9
functions.
.Sh SEE ALSO
.Xr config 1 ,
.Xr options 4 ,
.Xr CTASSERT 9 ,
.Xr panic 9 ,
.Xr printf 9
.Sh AUTHORS
These macros were written by
.An Chris G. Demetriou
.Aq cgd@netbsd.org .