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.\" $FreeBSD: head/share/man/man9/CTASSERT.9 286170 2015-08-02 00:22:14Z jmg $
.\"
.Dd August 1, 2015
.Dt CTASSERT 9
.Os
.Sh NAME
.Nm CTASSERT
.Nd compile time assertion macro
.Sh SYNOPSIS
.In sys/param.h
.In sys/systm.h
.Fn CTASSERT expression
.Sh DESCRIPTION
The
.Fn CTASSERT
macro is deprecated and the C11 standard
.Fn _Static_assert
should be used instead.
The header
.Fa sys/cdefs.h
should be included to provide compatibility for pre-C11 compilers.
.Pp
The
.Fn CTASSERT
macro evaluates
.Fa expression
at compile time and causes a compiler error if it is false.
.Pp
The
.Fn CTASSERT
macro is useful for asserting the size or alignment of important
data structures and variables during compilation, which would
otherwise cause the code to fail at run time.
.Sh EXAMPLES
Assert that the size of the
.Vt uuid
structure is 16 bytes.
.Pp
.Dl "CTASSERT(sizeof(struct uuid) == 16);"
.Sh SEE ALSO
.Xr KASSERT 9
.Sh AUTHORS
This manual page was written by
.An Hiten M. Pandya Aq Mt hmp@FreeBSD.org .