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CSC326H1 20199 631598475152ece326 final answer.pdf
CSC326H1_20199_631598475152ece326_final_answer.pdf
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CSC326H1 20199 631598475152ece326 final answer.pdf...
CSC326H1_20199_631598475152ece326_final_answer.pdf-Programming Languages Final Exam Solution ECE326,
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CSC326H1_20199_631598475152ece326_final_answer.pdf-Programming Languages Final Exam Solution ECE326,
Page 7
Programming Languages
Final Exam Solution
ECE326, Fall 2019
Question 4.
Object-Oriented Programming
[28 marks]
struct X {
char x[15];
virtual void foo() {
print("X.foo");
}
void bar() {
print("X.bar");
}
};
struct Y : X {
int y;
void bar() {
print("Y.bar");
}
void baz() {
print("Y.baz");
}
};
struct A {
int a;
virtual void qux()=0;
void baz() {
print("A.baz");
}
};
struct B : A {
long y;
virtual void tor() {
print("B.tor");
}
void bar() {
print("B.bar");
}
};
struct M : B, Y
{
int m;
virtual void qux() { print("M.qux"); }
virtual void tor() { print("M.tor"); }
};
int main() {
M mp;
Y & yp = mp;
X & xp = yp;
B & bp = mp;
A & ap = mp;
/* method calls for part d. */
return 0;
}
a)
Suppose the address of
mp
is
0x7ffd69d24c90
, what is the address of
yp
? [1 mark]
0x7ffd69d24ca8
Page 7 of 20
Page 8
Programming Languages
Final Exam Solution
ECE326, Fall 2019
b)
Draw the data structure layout for class M. Assume 8-byte alignment and the target architecture is
64-bit. Draw a line to show increasing address. [9 marks]
M
int m
4 bytes
Y
int y
4 bytes
X
padding
char c[15]
__vptr
1 byte
15 bytes
8 bytes
B
long b
8 bytes
A
padding
int a
__vptr
4 bytes
8 bytes
4 bytes
1 mark for each correctly placed variable/padding/vptr.
-1 mark per incorrectly placed class
-1 mark for extra padding/vptr
c)
For the inheritance hierarchy shown above, Write the entries in each of the five classes’ virtual table
in the correct order. Also state of the size of class M in bytes. [9 marks]
X::vtable
A::vtable
X::foo
nullptr
Y::vtable
B::vtable
X::foo
nullptr
B::tor
M::vtable
X::foo
M::qux
M::tor
sizeof(M) =
56
increasing
address
Page 8 of 20
Page 9
Programming Languages
Final Exam Solution
ECE326, Fall 2019
d)
What is the output for the following method calls? If the method call is illegal (either a runtime or
compile-time error), state the issue. [9 marks]
xp.foo()
X.foo
xp.bar()
X.bar
xp.baz()
Illegal – class X does not have method named baz
ap.qux()
M.qux
ap.tor()
Illegal – class A does not have method named tor
bp.tor()
M.tor
bp.baz()
A.baz
mp.foo()
X.foo
mp.bar()
Illegal – bar is ambiguous between X.bar and B.bar
Page 9 of 20
Page 10
Programming Languages
Final Exam Solution
ECE326, Fall 2019
Question 5.
Template Metaprogramming
[10 marks]
In assignment 3, one of the tasks involved was building the client to send request packets to the server.
Recall that the format of Value looks like this in a packet:
type
size
buf
4 bytes
4 bytes
size
bytes
Integer Example:
1
8
42
4 bytes
4 bytes
8 bytes
Where type is one of:
enum ValueType { INTEGER = 1, FLOAT = 2, STRING = 3, };
And that a Row contains an array of values like this:
count
value[0]
value[1]
...
value[count-1]
4 bytes
struct Request {
Packet packet;
void putvalue(long val);
void putvalue(double val);
void putvalue(const char *);
template<typename... Args>
void putrow(Args&&... args);
} req;
class Packet {
/* internal buffer */
public:
//
use this function to
//
add data to the end
//
of the buffer
void pack(const char * bytes,
int size);
};
a)
Complete the implementation for serializing a 64-bit integer into a packet. You do not have to
perform endianness conversion. The
type
field needs to be
INTEGER
, and the
size
field needs to
sizeof(long)
. Hint: use
packet.pack
to serialize data into the buffer. [0 marks]
void Request::putvalue(long val) {
int temp = INTEGER;
packet.pack((const char *)&temp, sizeof(int));
temp = sizeof(long);
packet.pack((const char *)&temp, sizeof(int));
packet.pack((const char *)&val, temp);
/* 1 mark for each line of code */
/* THIS QUESTION WAS REMOVED FROM FINAL EXAM */
/* DO NOT MARK */
}
Page 10 of 20
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