<s>
Extended	B-Application
static	I-Application
checking	I-Application
(	O
ESC	O
)	O
is	O
a	O
collective	O
name	O
in	O
computer	B-General_Concept
science	I-General_Concept
for	O
a	O
range	O
of	O
techniques	O
for	O
statically	O
checking	O
the	O
correctness	O
of	O
various	O
program	O
constraints	O
.	O
</s>
<s>
As	O
with	O
type	O
checking	O
,	O
ESC	O
is	O
performed	O
automatically	O
at	O
compile	B-Application
time	I-Application
(	O
i.e.	O
</s>
<s>
ESC	O
can	O
identify	O
a	O
range	O
of	O
errors	O
which	O
are	O
currently	O
outside	O
the	O
scope	O
of	O
a	O
type	O
checker	O
,	O
including	O
division	B-Algorithm
by	I-Algorithm
zero	I-Algorithm
,	O
array	B-Data_Structure
out	I-Data_Structure
of	I-Data_Structure
bounds	I-Data_Structure
,	O
integer	B-Error_Name
overflow	I-Error_Name
and	O
null	O
dereferences	O
.	O
</s>
<s>
The	O
techniques	O
used	O
in	O
extended	B-Application
static	I-Application
checking	I-Application
come	O
from	O
various	O
fields	O
of	O
computer	B-General_Concept
science	I-General_Concept
,	O
including	O
static	O
program	O
analysis	O
,	O
symbolic	B-Application
simulation	I-Application
,	O
model	B-Application
checking	I-Application
,	O
abstract	O
interpretation	O
,	O
SAT	B-Application
solving	I-Application
and	O
automated	B-Application
theorem	I-Application
proving	I-Application
and	O
type	O
checking	O
.	O
</s>
<s>
Extended	B-Application
static	I-Application
checking	I-Application
is	O
generally	O
performed	O
only	O
at	O
an	O
intraprocedural	O
,	O
rather	O
than	O
interprocedural	O
,	O
level	O
in	O
order	O
to	O
scale	O
to	O
large	O
programs	O
.	O
</s>
<s>
Furthermore	O
,	O
extended	B-Application
static	I-Application
checking	I-Application
aims	O
to	O
report	O
errors	O
by	O
exploiting	O
user-supplied	O
specifications	O
,	O
in	O
the	O
form	O
of	O
pre	O
-	O
and	O
post-conditions	O
,	O
loop	B-Application
invariants	I-Application
and	O
class	B-Application
invariants	I-Application
.	O
</s>
<s>
All	O
verification	O
conditions	O
must	O
be	O
shown	O
to	O
be	O
false	O
(	O
hence	O
correct	O
by	O
means	O
of	O
excluded	O
third	O
)	O
in	O
order	O
for	O
a	O
method	O
to	O
pass	O
extended	B-Application
static	I-Application
checking	I-Application
(	O
or	O
"	O
unable	O
to	O
find	O
more	O
errors	O
"	O
)	O
.	O
</s>
<s>
Typically	O
,	O
some	O
form	O
of	O
automated	B-Application
theorem	I-Application
prover	I-Application
is	O
used	O
to	O
discharge	O
verification	O
conditions	O
.	O
</s>
<s>
Extended	B-Application
Static	I-Application
Checking	I-Application
was	O
pioneered	O
in	O
ESC/Modula	O
-3	O
and	O
,	O
later	O
,	O
ESC/Java	B-Application
.	O
</s>
<s>
Its	O
roots	O
originate	O
from	O
more	O
simplistic	O
static	O
checking	O
techniques	O
,	O
such	O
as	O
static	O
debugging	O
or	O
Lint	B-Device
(	O
software	O
)	O
and	O
FindBugs	B-Language
.	O
</s>
<s>
A	O
number	O
of	O
other	O
languages	O
have	O
adopted	O
ESC	O
,	O
including	O
Spec#	O
and	O
SPARKada	B-Language
and	O
VHDL	B-Language
VSPEC	O
.	O
</s>
<s>
However	O
,	O
there	O
is	O
currently	O
no	O
widely	O
used	O
software	O
programming	O
language	O
that	O
provides	O
extended	B-Application
static	I-Application
checking	I-Application
in	O
its	O
base	O
development	O
environment	O
.	O
</s>
