.\" $OpenBSD: ASN1_NULL_new.3,v 1.3 2021/12/09 18:42:35 schwarze Exp $
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.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
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.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 .