<s>
Void	B-Application
safety	I-Application
(	O
also	O
known	O
as	O
null	B-Application
safety	I-Application
)	O
is	O
a	O
guarantee	O
within	O
an	O
object-oriented	B-Language
programming	I-Language
language	I-Language
that	O
no	O
object	O
references	O
will	O
have	O
null	O
or	O
void	O
values	O
.	O
</s>
<s>
In	O
object-oriented	B-Language
languages	I-Language
,	O
access	O
to	O
objects	O
is	O
achieved	O
through	O
references	O
(	O
or	O
,	O
equivalently	O
,	O
pointers	O
)	O
.	O
</s>
<s>
In	O
such	O
cases	O
,	O
the	O
call	O
above	O
will	O
be	O
a	O
void	O
call	O
,	O
leading	O
to	O
a	O
run-time	O
exception	B-General_Concept
,	O
often	O
resulting	O
in	O
abnormal	B-General_Concept
termination	I-General_Concept
of	O
the	O
program	O
.	O
</s>
<s>
Void	B-Application
safety	I-Application
is	O
a	O
static	O
(	O
compile-time	O
)	O
guarantee	O
that	O
a	O
void	O
call	O
will	O
never	O
arise	O
.	O
</s>
<s>
In	O
a	O
2009	O
talk	O
,	O
Tony	O
Hoare	O
traced	O
the	O
invention	O
of	O
the	O
null	O
pointer	O
to	O
his	O
design	O
of	O
the	O
ALGOL	B-Language
W	I-Language
language	O
and	O
called	O
it	O
a	O
"	O
mistake	O
"	O
:	O
</s>
<s>
Bertrand	O
Meyer	O
introduced	O
the	O
term	O
"	O
void	B-Application
safety	I-Application
"	O
.	O
</s>
<s>
An	O
early	O
attempt	O
to	O
guarantee	O
void	B-Application
safety	I-Application
was	O
the	O
design	O
of	O
the	O
Self	B-Operating_System
programming	I-Operating_System
language	I-Operating_System
.	O
</s>
<s>
The	O
Eiffel	B-Language
language	I-Language
is	O
void-safe	O
according	O
to	O
its	O
ISO-ECMA	O
standard	O
;	O
the	O
void-safety	O
mechanism	O
is	O
implemented	O
in	O
EiffelStudio	B-Application
starting	O
with	O
and	O
using	O
a	O
modern	O
syntax	O
starting	O
with	O
.	O
</s>
<s>
The	O
Spec#	O
language	O
,	O
a	O
research	O
language	O
from	O
Microsoft	O
Research	O
,	O
has	O
a	O
notion	O
of	O
"	O
non-nullable	O
type	O
"	O
addressing	O
void	B-Application
safety	I-Application
.	O
</s>
<s>
The	O
F#	B-Operating_System
language	I-Operating_System
,	O
a	O
functional-first	O
language	O
from	O
Microsoft	O
Research	O
running	O
on	O
.NET	O
framework	O
,	O
is	O
void-safe	O
except	O
when	O
interoperating	O
with	O
other	O
.NET	O
languages	O
.	O
</s>
<s>
The	O
null	B-Application
safety	I-Application
based	O
in	O
types	O
appeared	O
first	O
in	O
the	O
Ceylon	B-Language
,	O
followed	O
soon	O
by	O
TypeScript	B-Language
.	O
</s>
<s>
The	O
C#	B-Application
language	O
implements	O
compile-time	O
null	B-Application
safety	I-Application
check	O
since	O
version	O
8	O
.	O
</s>
<s>
Other	O
languages	O
that	O
use	O
null-safe	O
types	O
by	O
default	O
include	O
JetBrains	O
 '	O
Kotlin	B-Language
,	O
Rust	B-Application
,	O
and	O
Apple	O
's	O
Swift	B-Application
.	O
</s>
