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L. Dillon, CSE 452, Fall 2008
1
Binding
is the process by which
A routine invocation is attached to code that is executed
An attribute reference is connected a memory location
Binding can be done•
At compile time —
static binding, using static linking
At program load time
static binding, using dynamic
At run time — linking
dynamic binding
Binding
L. Dillon, CSE 452, Fall 2008
In the .h (header) file:
extern
int
foo
(arg
c);
extern
float
my_variable;
In the .c file:
int
foo
(arg
c);
float
my_variable;
Static binding in C
L. Dillon, CSE 452, Fall 2008
3
On the caller side:
Push the actual parameters on the stack.
Push the return address on the stack
Jump to the code for the callee
Address to jump to is “filled out” during linking
On callee side:
Push space for local variables and initialize, as needed
Execute the statements in the routine’s body
Read the return address from the stack
Pop local variables, return address and actual params
Jump to return address
Execution of a call in C
L. Dillon, CSE 452, Fall 2008
L. Dillon, CSE 452, Fall 2008
5
Identifiers used in program are relative to an object Dynamic binding is used in OO
In
a
, attribute
a
belongs to
Current
In
foo(...)
, routine
foo
belongs to
Current
In
obj.foo(...)
, routine
foo
belongs to target object
obj
Routines may be redefined in subclasses
Dynamic binding and OO
L. Dillon, CSE 452, Fall 2008
Objects and class tables
class
A
create
set
feature
a:
INTEGER
set(n:
INTEGER)
is
do
a
n
end
get_a
INTEGER
is
do
Result
a
end
f(n:
INTEGER):
like
Current
is
do
create
Result.set(n
a)
end
Current
A class table
INT field
return first field of Currentstore n in first field of Current
call Result.set(n+a):initialize the new A object’s class table ptr & fields (to default vals);allocate space for a new A object, and bind it to Result;
push return address & jump to first routine in Current’s class tableread n; add first field of Current; push sum onto stack (for callee’s n)push Result onto stack (for callee’s Current)
return r
L. Dillon, CSE 452, Fall 2008
7
Modelling single inheritance
class
B
inherit
A
redefine
set
end
create
set
feature
b:
INTEGER
set(n:
INTEGER)
is
do
a
n;
b
n
end
get_b:
INTEGER
is
do
Result
b
end
end
B^ A
A class table
INT field
B class table
INT fieldINT field
B’s get_bB’s fB’s set A’s fA’s get_aA’s set
L. Dillon, CSE 452, Fall 2008 class
A
create
set
feature
a: INTEGER
set(n:
INTEGER)
is
do
a := n end
f(n:
INTEGER):
like
Current
is
do
create
Result.set(n
a) end
get_a
INTEGER
is
do
Result
a end
end
A
class
B
inherit
A
redefine
set
end
create
set
feature
b: INTEGER
set(n:
INTEGER)
is
do
a := n; b := n end
get_b:
INTEGER
is
do
Result
b end
end
B
class
MAIN
create
make
feature
make
is
local
a: A
b1,
b2:
B
do
create
b1.set(1)
a :=
b1.f
b ?=
a
end
end
MAIN
L. Dillon, CSE 452, Fall 2008
13
Modelling multiple inheritance
Need a “view” of each parent in an heir:
C
A
B
a
b
c
f
ctp: g a:
ctp: b:
g:^ B’s table f: A’s table
B’s gcode forA’s f code for
h
x:
C
C-as-A table h: f:
C-as-B table g:
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
C’s h code for
x:
...
Fx.g: (^) push
(^) x (^) onto stack (for callee’s
(^) Current
F
(^) push return address & jump to code for
(^) g (^) (found at
(^) ((x+
Code for
B
’s (^) g (^) expects:
F
b (^) at (^) Current+
F
code for
(^) g (^) at
**Current
size 4) (assuming ptrs & ints of
L. Dillon, CSE 452, Fall 2008
Modelling multiple inheritance
Need a “view” of each parent in an heir:
C
A
B
a
b
c
f
ctp: g a:
ctp: b:
g: B’s table f: A’s table
B’s gcode forA’s f code for
h
x:
C
C-as-A table h: f:
C-as-B table g:
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
C’s h code for
x:
...
F x.g: push
(^) x+
(^) onto stack (for callee’s
(^) Current
F
push return address & jump to code for
(^) g (^) (found at
(^) ((x+
Code for
B
’s (^) g (^) expects:
F
(^) b (^) at (^) Current+
F
(^) code for
(^) g (^) at
**Current
size 4) (assuming ptrs & ints of
L. Dillon, CSE 452, Fall 2008
15
Modelling multiple inheritance
Need a “view” of each parent in an heir:
C
A
B
a
b
c
f
ctp: g a:
ctp: b:
g:^ B’s table f: A’s table
B’s gcode forA’s f code for
h
x:
C
C-as-A table h: f:
C-as-B table g:
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
C’s h code for
x:
...
y := x :
F
(^) “normal” assignment
y:
A
z:
B
y:
...
L. Dillon, CSE 452, Fall 2008
Modelling multiple inheritance
Need a “view” of each parent in an heir:
C
A
B
a
b
c
f
ctp: g a:
ctp: b:
g: B’s table f: A’s table
B’s gcode forA’s f code for
h
x:
C
C-as-A table h: f:
C-as-B table g:
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
C’s h code for
x:
...
y:
A
z:
B
z := x :
F
store
x+
(^) into location bound to
(^) z
z:
...
Modelling adaptation of parent(s)
C
A
B
a
b
c
f
hg
redefine
h
rename
f as
k
ctp: a:
ctp: b:
h: g: B’s table f: A’s table
B’s hcode forB’s gcode forA’s f code for
Modelling adaptation of parent(s)
C
A
B
a
b
c
f
hg
redefine
h
rename
f as k
ctp: a:
ctp: b:
h: g: B’s table f: A’s table
B’s hcode forB’s gcode forA’s f code for
Adapt views of parent(s) in an heir:
x:
C
h: 8 g: 0 C-as-B table h: 0 k: 0 C-as-A table
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
x:
...
C’s h code for
Modelling adaptation of parent(s)
C
A
B
a
b
c
f
hg
redefine
h
rename
f as
k
ctp: a:
ctp: b:
h: g: B’s table f: A’s table
B’s hcode forB’s gcode forA’s f code for
Adapt views of parent(s) in an heir:
x:
C
h: 8 g: 0 C-as-B table h: 0 k: 0 C-as-A table
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
x:
...
C’s h code for
F x.k: (^) push
(^) x (^) onto stack (for callee’s
(^) Current
F
(^) push return address & jump to code for
(^) k (^) (code for A’s f, found at
(x)
obvious amounts.)address calculation by theconstants used in thepresence affects thebe explained later; theirthese “displacements” willing slides; the purpose ofhere and in the remain-address calculationsthe tables in theignoring the numbers in (For simplicity, I am
Modelling adaptation of parent(s)
C
A
B
a
b
c
f
hg
redefine
h
rename
f as k
ctp: a:
ctp: b:
h: g: B’s table f: A’s table
B’s hcode forB’s gcode forA’s f code for
x:
C
y:
A
Adapt views of parent(s) in an heir:
h: 8 g: 0 C-as-B table h: 0 k: 0 C-as-A table
B’s gcode forA’s f code for
ctp: a:
ctp: c:b:
x:
...
C’s h code for
y:
...
F y.f: push
(^) y (^) onto stack (for callee’s
(^) Current
F
push return address & jump to code for
(^) f (^) (found at
(^) (y)
y := x
F
(^) “normal” assignment
L. Dillon, CSE 452, Fall 2008
25
class
A
feature a: INTEGER
set(n:
INTEGER)
is
do
a :=
n end
f(n:
INTEGER):
like
Current
is
do
create
Result
Result.set(n
a)
end
get
INTEGER
is
do
Result
a end
end
A
class
B
feature b: INTEGER
set(n:
INTEGER)
is
do
b := n end
get:
INTEGER
is
do
Result
b end
end
B
class
C
inherit
A
rename set
as
set1,
get
as
get
end
B
rename set
as
set
redefine
get
end
feature c:
INTEGER
get
INTEGER
is
do
Result
c
b end
g is
do c := a
b end
end
C
class
MAIN
create
make
feature make
is
local a: A; b: B;
c:C
do
create
c
c.set1(1);
c.set2(2);
c.g
a := c; b:=
c;
end
end
MAIN
L. Dillon, CSE 452, Fall 2008
Exercise
a.a;the ellipses?What results are returned by the following invocations atclass (feature) tables.ellipses (.. .) in execution of Main. Include drawings of theDraw the stack and the heap when control reaches the
a.get
b.b;
b.get
c.a;
c.b;
c.c;
c.get1;
c.get
