1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)assert.3 8.1 (Berkeley) 6/9/93 29.\" $FreeBSD$ 30.\" 31.Dd January 26, 1999 32.Dt ASSERT 3 33.Os 34.Sh NAME 35.Nm assert 36.Nd expression verification macro 37.Sh SYNOPSIS 38.In assert.h 39.Fn assert expression 40.Sh DESCRIPTION 41The 42.Fn assert 43macro tests the given 44.Ar expression 45and if it is false, 46the calling process is terminated. 47A 48diagnostic message is written to 49.Dv stderr 50and the function 51.Xr abort 3 52is called, effectively terminating the program. 53.Pp 54If 55.Ar expression 56is true, 57the 58.Fn assert 59macro does nothing. 60.Pp 61The 62.Fn assert 63macro 64may be removed at compile time by defining 65.Dv NDEBUG 66as a macro 67(e.g., by using the 68.Xr cc 1 69option 70.Fl D Ns Dv NDEBUG ) . 71.Sh EXAMPLES 72The assertion: 73.Pp 74.Dl "assert(1 == 0);" 75.Pp 76generates a diagnostic message similar to the following: 77.Pp 78.Dl "Assertion failed: (1 == 0), function main, file assertion.c, line 100." 79.Sh SEE ALSO 80.Xr abort 3 81.Sh STANDARDS 82The 83.Fn assert 84macro conforms to 85.St -isoC-99 . 86.Sh HISTORY 87An 88.Nm 89macro appeared in 90.At v6 . 91