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.\" $OpenBSD: ASN1_NULL_new.3,v 1.3 2021/12/09 18:42:35 schwarze Exp $
.\"
.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: December 9 2021 $
.Dt ASN1_NULL_NEW 3
.Os
.Sh NAME
.Nm ASN1_NULL_new ,
.Nm ASN1_NULL_free
.Nd ASN.1 NULL value
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_NULL *
.Fn ASN1_NULL_new void
.Ft void
.Fn ASN1_NULL_free "ASN1_NULL *val_in"
.Sh DESCRIPTION
.Fn ASN1_NULL_new
returns a specific invalid pointer that represents the ASN.1 NULL value,
which is the only possible value of the ASN.1 NULL type.
That pointer is different from a
.Dv NULL
pointer.
Dereferencing it almost certainly results in a segmentation fault.
This function does not allocate memory and cannot fail.
.Pp
.Fn ASN1_NULL_free
has no effect whatsoever.
In particular, it ignores the
.Fa val_in
argument and does not free any memory.
In normal use, application programs only pass the invalid pointer
obtained from
.Fn ASN1_NULL_new
to this function.
But even if a valid pointer is passed, that pointer does not become invalid.
.Pp
The ASN.1 NULL type is also represented by the
.Dv V_ASN1_NULL
type identifier constant.
.Sh SEE ALSO
.Xr ASN1_item_new 3 ,
.Xr d2i_ASN1_NULL 3
.Sh STANDARDS
ITU-T Recommendation X.208, also known as ISO/IEC 8824-1:
Specification of Abstract Syntax Notation One (ASN.1),
section 19: Notation for the null type
.Sh HISTORY
.Fn ASN1_NULL_new
and
.Fn ASN1_NULL_free
first appeared in OpenSSL 0.9.5 and have been available since
.Ox 2.7 .
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