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.\"     @(#)assert.3	8.1 (Berkeley) 6/9/93
.\"
.Dd June 1, 2016
.Dt ASSERT 3
.Os
.Sh NAME
.Nm assert
.Nd expression verification macro
.Sh SYNOPSIS
.In assert.h
.Fn assert expression
.Sh DESCRIPTION
The
.Fn assert
macro tests the given
.Ar expression
and if it is false,
the calling process is terminated.
A diagnostic message, consisting of the text of the expression,
the name of the source file, the line number and the enclosing
function,
is written to
.Em stderr
and the
.Xr abort 3
function is called, effectively terminating the program.
.Pp
If
.Ar expression
is true,
the
.Fn assert
macro does nothing.
.Pp
The
.Fn assert
macro
may be removed at compile time with
the
.Xr cc 1
option
.Fl DNDEBUG .
.Sh DIAGNOSTICS
The following diagnostic message is written to
.Em stderr
if
.Ar expression
is false:
.Bd -literal -offset indent
"assertion \e"%s\e" failed: file \e"%s\e", line %d, function \e"%s\e"\en", \e
		    "expression", __FILE__, __LINE__, __func__);
.Ed
.Sh SEE ALSO
.Xr cc 1 ,
.Xr _DIAGASSERT 3 ,
.Xr abort 3
.Sh STANDARDS
The
.Fn assert
macro conforms to
.St -isoC-99 .
.Sh HISTORY
A
.Nm
macro appeared in
.At v7 .
.Pp
Information on the name of the enclosing function appeared in
.St -isoC-99 .