.\"	$NetBSD: _DIAGASSERT.3,v 1.4 2002/02/13 08:17:28 ross Exp $
.\"
.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Luke Mewburn.
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.Dd January 4, 2001
.Dt _DIAGASSERT 3
.Os
.Sh NAME
.Nm _DIAGASSERT
.Nd expression verification macro
.Sh SYNOPSIS
.Fd #include \*[Lt]assert.h\*[Gt]
.Fn _DIAGASSERT expression
.Sh DESCRIPTION
The
.Fn _DIAGASSERT
macro tests the given
.Ar expression
and if it is false, one or more of the following may occur:
.Bl -bullet -offset indent
.It
a diagnostic message may be logged to the system logger with
.Xr syslog 3 .
This is default behaviour.
.It
a diagnostic message may be printed to the
.Dv stderr
stream.
.It
the calling process will be terminated by calling
.Xr abort 3 .
.El
.Pp
This behaviour may be changed by setting the
.Ev LIBC_DIAGASSERT
environment variable (see below).
.Pp
The diagnostic message consists of the text of the expression,
the name of the source file, the line number and the enclosing
function.
.Pp
If
.Ar expression
is true,
the
.Fn _DIAGASSERT
macro does nothing.
.Pp
The
.Fn _DIAGASSERT
macro is not compiled in by default, and will only be compiled in with the
.Xr cc 1
option
.Fl D_DIAGNOSTIC .
.Pp
This macro is used in the various system libraries such as the
.Lb libc
to ensure that various library calls are invoked with valid arguments.
.Sh ENVIRONMENT
The
.Ev LIBC_DIAGNOSTIC
environment variable can be used to modify the default behaviour of
logging the assertion to the system logger.
.Pp
.Ev LIBC_DIAGNOSTIC
may be set to one or more of the following characters:
.Bl -tag -width xxx -offset indent
.It a
.Xr abort 3
once any assertion messages have been logged and/or printed.
.It A
Opposite of
.Dq a .
.It e
Print the assertion message to the
.Dv stderr
stream.
.It E
Opposite of
.Dq e .
.It l
Log the assertion message with
.Xr syslog 3
to the facility
.Dv user.debug .
.It L
Opposite of
.Dq l .
.El
.Sh DIAGNOSTICS
The diagnostic message has the following format:
.Bd -literal -offset indent
"assertion \e"%s\e" failed: file \e"%s\e", line %d, function \e"%s\e"\en",
	    "expression", __FILE__, __LINE__, __func__
.Ed
.Sh SEE ALSO
.Xr cc 1 ,
.Xr abort 3 ,
.Xr assert 3
.Sh HISTORY
The
.Nm _DIAGASSERT
macro appeared in
.Nx 1.5 .