Getting Started Cpp

Outline

Preparation

Getting Start

OOP

Memory management

Rest of C/C++ features

Appendix 2

Outline

Preparation

Getting Start

OOP

Memory management


Appendix

Hello world

C/C++ files

Entry point

C/C++ libraries

Source compile process

3

Outline

Preparation

Getting Start

OOP

Memory management


Appendix

Variables and constant

Primary data type

Array – Pointer – String

Data structure: enum – union - struct

Function

Namespace

4

Outline

Preparation

Getting Start

OOP

Memory management


Appendix

Class & Object

Inheritance

Polymorphism

Operator overloading

Class’ static member 5

Outline

Preparation

Getting Start

OOP

Memory management


Appendix

Recall pointer

Memory leak

6

Outline

Preparation

Getting Start

OOP

Memory management


Appendix

Forward declaration

Standard IO – Console IO & FILE

Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 7

Outline

Preparation

Getting Start

OOP

Memory management


Hello world!

C/C++ files

Entry point

C/C++ libraries


8

Outline

Preparation

Getting Start

Basic Data Structure

OOP

Memory management


Hello world!

C/C++ files

Entry point

C/C++ libraries


9

Hello world using VS

10

Hello world

# include <stdio.h>

void main()

{

printf("Hello world");

}

main.cpp

Use standard IO lib

Entry point

Print to console screen

11

Outline

Preparation

Getting Start

OOP

Memory management


Hello world!

C/C++ files

Entry point

C/C++ libraries


12

C/C++ source files

Header file (.h) aka include file Hold declarations for other files

use (prototype) Not required

#include "stdio.h"

void Todo1();

void Todo2();

# include "header.h"

void Todo1()

{

Todo2();

}

void Todo2(){}

void main()

{

Todo1();

}

Source file (.c / .cpp) Content implementation

Required

13

Outline

Preparation

Getting Start

OOP

Memory management


Hello world!

C/C++ files

Entry point

C/C++ libraries


14

Entry point

Required unique entry point

The most common is: main void main()

{

// your code here

}

Form1.cpp

int main(int n, char ** args)

{

// your code here

}

Form2.cpp

1>LINK : fatal error LNK1561: entry point must be defined

Error when no entry point is defined

15

Outline

Preparation

Getting Start

OOP

Memory management


Hello world!

C/C++ files

Entry point

C/C++ libraries


16

C/C++ standard library

C/C++ support a set of internal basic library, such as • Basic IO

• Math

• Memory handle

• …

For using, include the header file

#include <…>

#include "…"

#include "stdio.h"

void main()

{

printf("hello");

}

17

C header C++ header

<assert.h> <cassert> Content assert macro, for debugging

<Ctype.h> <cctype> For character classification/convert functions

<Errno.h> <cerrno> For testing error number

<float.h> <cfloat> Floating point macros

<limits.h> <climits> Define range of value of common type

<math.h> <cmath> Mathematical functions

<setjmp.h> <csetjmp> Provide “non-local jumps” for flow control

<signal.h> <csignal> Controlling various exceptional conditions

<stdlib.h> <cstdlib> Standard lib

<stddef.h> <cstddef>

<stdarg.h> <cstdarg>

<stdio.h> <cstdio> Standard IO

<string.h> <cstring> Manipulating several kinds of string

<time.h> <ctime> Converting between time & date formats

<wchar.h> <cwchar>

<wctype> <cwctype> 18

C/C++ user-defined lib

Not C/C++ standard lib

Come from:

• Third-party

• User own

In common, include 2 parts

• .h files & .lib files: for developer

• .dll file (dynamic library): for end-user

error LNK2019: unresolved external symbol

Error caused when forget to add .lib file

19

C/C++ user-defined lib (cont.)

For using

• Include .h files

• Inform .lib files to compiler

• Copy all .dll file to (if any) :

o same folder with execute file, or

o to system32 (windows) – not recommend

20

Declare path to .lib

Import user-defined library Visual studio

21

Import user-defined library Visual studio

Declare .lib file

22

Outline

Preparation

Getting Start

OOP

Memory management


C/C++ files

Entry point

C/C++ libraries

Hello world!


23

Process

Source

.h/.c/.cpp preprocess

Preprocessed source

Compile

.o / .obj

(object file) Linker Executable/

lib

Tools: • Visual Studio: cl.exe (Press F7 / F5) • GNU GCC: gcc/ g++

24

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type

Array – Pointer - String


Function

Namespace

25

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type



Function

Namespace

26

Variable classification

Scope:

• Local variable

• Global variable

• Static variable

Storage class specifier

• auto

• static

• register

• extern

27

Global & local int mGlobalVar;

void Foo()

{

int localVar;

printf("Foo : %d %d\n",

localVar, mGlobalVar);

}

int main()

{

int localVar = 1;

printf("Main: %d %d\n",

localVar, mGlobalVar);

mGlobalVar = 1;

Foo();

return 1;

}

Global variable

• Available in all of program • Set default value to zero

Local variable • NO default value • Available inside block

Main: 1 0

Foo : 2280752 1

Command prompt

28

Auto variable

As default, a variable is a auto variable

int myVar auto int myVar

Go out of scope once the program exits from the current block

29

Static variable

Allocated when the program starts and is deallocated when the program ends.

Default value is zero (0)

#include <cstdio>

static int s_iGlobalStatic;

void Foo()

{

static int s_iLocalStatic;

printf("Foo: called %d\n",

s_iLocalStatic++);

}

int main()

{

int localVar = 1;

printf("Main: %d\n",

s_iGlobalStatic);

Foo();

Foo();

Foo();

return 1;

}

Main: 0

Foo: called 0

Foo: called 1

Foo: called 2

Command prompt

30

Register variable

Stored in a machine register if possible

Usually used in “for iterator” for improve performance

int main()

{

int sum = 0;

for (register int i = 0;

i < 100;

i++)

{

sum += i;

}

printf("Sum = %d\n", sum);

return 1;

}

31

Extern variable

Specify that the variable is declared in a different file.

Compiler will not allocate memory for the variable

Avoid duplicate declaration

Share (global) variable for multiple .cpp files

#include <cstdio>

extern int m_iExternVar;

int main()

{

printf("Value = %d\n",

m_iExternVar);

return 1;

}

main.cpp

int m_iExternVar = 100;

Extern.cpp

Value = 100

Command prompt

32

Constant

Variable's value is constant

To prevent the programmer from modifying

int const k_Hello = 0;

int main()

{

k_Hello = 10;

}

error C3892: 'k_Hello' : you cannot assign to a variable that is const

Error

33

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type



Function

Namespace

34

Primitive data type (32bits processor)

Type Size Range

void n/a

char 1 byte unsigned char: -128 … 127 signed char: 0…255

short 2 bytes unsigned short: 0 … (216 -1) signed short: -215 … (215 – 1)

int 4 bytes -231 … (231 – 1)

unsigned int: 0 … (232 -1) signed int: -231 … (231 – 1)

long 4 bytes -231 … (231 – 1)

unsigned long: 0 … (232 -1) signed long: -231 … (231 – 1)

long long 8 bytes -263 … (263 – 1)

unsigned long long: 0 … (264 -1) signed long long: -263 … (263 – 1)

bool 1 byte True /false (non-zero / zero)

float 4 bytes

double 8 bytes 35

New type definition

Use typedef

36

typedef int Mytype;

typedef int MyArr[5];

Mytype var1;

MyArr arr;

sizeof operator

0 Return size (in byte) of a type, data structure, variable

int sizeInt = sizeof(int);

int sizeLong = sizeof(long);

char a;

int sizeA = sizeof(a);

Return 4

Return 4

Return 1

37

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type



Function

Namespace

38

Array

Used to store consecutive values of the same data types

int b[4] = {1, 2, 3, 4};

n-dimensions array

int b[<s1>][<s2>]…[<sn>] si MUST BE constant

Index of array is counted from 0 to (si-1) C/C++ do not handle out-of-range exception

int b[4] = {1, 2, 3, 4};

for (int i = 0; i < 4; i++)

{

printf("%d\n", b[i]);

}

printf("%d\n", b[10]);

b[10] = ?

39

Array Assignment

40

int a[4] = {1, 2, 3, 4};

int a[] = {1, 2, 3, 4};

int a[4];

a[0] = 1;

a[1] = 2;

a[2] = 3;

a[3] = 4;

int a[4] = {1};

a[0], a[1], a[2], a[3] = ?

int a[4];

memset(a, 0, 4*sizeof(int));

Array Assignment 2D Array

41

int a[3][2];

a[0][0] = 1;

a[0][1] = 2;

a[1][0] = 3;

a[1][1] = 4;

a[2][0] = 5;

a[2][1] = 6;

int a[3][2] = {1, 2, 3, 4, 5, 6};

int a[3][2];

memset(a, 0, 6*sizeof(int));

int a[][2] = {1, 2, 3, 4, 5, 6};

Same as 1D. Why?

int a[3][2] = {

{1, 2},

{3, 4},

{5, 6}

};

Pointer

Computer's memory is made up of bytes.

Each byte has a number, an address, associated with it.

0x01 0x02 0x03 0x01 0x05 0x06 0x07 0x08

When storing a variable, such as int i = 1

0x00 0x00 0x00 0x01

0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08

i

o i = 1

o &i = 0x01 & operator: get address of a variable

42

http://augustcouncil.com/~tgibson/tutorial/addressDef.html

Pointer (cont.)

For storing address of a variable, use a special type: pointer

int *pi; char *pc; float *pf;

Pointer of a integer variable

Pointer of a char variable

Pointer of a float variable

int *pi = &i;

43

int* pi;

pi = &i;

0x10 0x00 0x00 0x00

0xF1 0xF2 0xF3 0xF4 0xF5 0xF6 0xF7 0xF8

i

&i

Pointer (cont.)

Pointer is also a variable it’s stored in memory

int i = 10;

int *p i = 10 0x2f00002c

0x2f00aabb p p = &p =

*p =

*p : get value at address pointed by p

44

0x2f00002c

0x2f00aabb

10

= &i;

= 0x2f00002c

Pointer (cont.)

Type of pointer notify that how to get the value pointed by pointer

int i = 0x3f20cc01;

char *p1 = (char *)&i;

short *p2 = (short *)&i;

int *p3 = &i;

p1 is pointed to char-block. *p1 =

p2 is pointed to short-block. *p2 =

p3 is pointed to int-block. *p3 =

P1 P2

0x01 0xcc 0x20 0x3f

0xF1 0xF2 0xF3 0xF4 0xF5 0xF6 0xF7 0xF8

i Little Endian

P3

45

0x01

0xCC01

0x3f20cc01

Pointer (cont.) sizeof operator

Size of pointer is not belong to type of pointer Size of pointer depend on processor (16 bits, 32 bits, 64

bits) • For windows 32 bits: size of pointer is 4 bytes

int main()

{

char c = 0;

char *p = &c;

printf("size = %d", sizeof(p));

}

46

Pointer pointer operator

Note: each step is a distance k bytes belongs to type of pointer:

• byte: 1 byte

• Short: 2 byte

• ….

Operator

desc Example

+ move forward n steps p += 10;

- move backward n step p -= 1;

++ move forward 1 step p++;

-- move backward 1 step p--;

0x01 0xcc 0x20 0x3f 0x00 0x10 0xaa

0x01 0x02 0x03 0x04 0x05 0x06 0x07

p1 p1+1 p1+5

0x01 0xcc 0x20 0x3f 0x00 0x10 0xaa

0x01 0x02 0x03 0x04 0x05 0x06 0x07

p2 p2+1 p2+3

char *p1; short *p2;

(p1+1) (p2 + 1) *(p1+1) *(p2+1) &(p1+1) &(p2+1)

47

Pointer pointer operator - Practice

48

char a[6] = {10, 20, 30, 40, 50, 60};

char *p = a;

a

0x001cff08

p 0x001cff04

a = ?

&a = ?

*a = ?

p = ?

&p = ?

*p = ?

p + 1 = ?

(*p) + 1 = ?

*(p + 1) = ?

&p + 1;

&a + 1

a++; a = ?

p++; p = ?

Pointer to pointer

Recall that, a pointer variable is a variable.

To store address of a pointer variable, we use pointer-to-pointer variable.

49

int iVar = 10;

int *p1 = &iVar;

int **p2 = &p1;

iVar = 10

p1 = 0x100

p2 = 0x200

0x200

0x100

0x300

*p1 == ?

*p2 == ?

*(*p2) == ?

p

nx4 bytes

Pointer Dynamic allocation

Static allocation: int a = 10;

int array[1000];

• Variable will be allocated in stack limited size • Number of elements of array is const • Can not clean up when they become useless

Dynamic allocation • User pointer • Allocation a block of memory in heap high capacity • Clean up easily

Alloc n-int elements in heap

int *p = new int[n];

p

Free memory block pointed by p

50

delete p;

How about “p” after deleting?

Pointer Dynamic allocation (cont.) There two way for dynamic allocation

51

• Using stdlib.h

• Using malloc/free

Old C style

• Using new/delete

• Using new[] / delete[]

C++ style

int main()

{

char *i = (char*) malloc (100);

// some code here

free(i);

}

int main()

{

char *i = new char[100];

// some code here

delete []i;

}

Pointer Dynamic allocation (cont.)

Use delete for new, Use delete[] for new[]

52

struct A

{

public:

static int count;

int val;

A()

{

printf("Created %d\n",

val = count++);}

~A()

{

printf("Deleted %d\n",

val);}

};

int A::count = 0;

int main()

{

A *cA = new A[10];

delete cA;

return 1;

}

Delete cA[0] only

int main()

{

A *cA = new A[10];

delete []cA;

return 1;

}

Delete all cA

Pointer-to-pointer dynamic allocation

In common, used for allocation an 2D-array

53

int **p;

p = new int*[2];

*(p+0) = new int;

*(p+1) = new int;

p 0x900

0x500

= 0x500

0x200

0x200

0x300

0x300

int **p = new int*[3];

p[0] = new int[4];

p[1] = new int[4];

p[2] = new int[4];

*(*(p + i) +j ) p[i][j]

Pointer vs. Array

In common, pointer could be used like array

int main()

{

int *p

p[0] = 1;

*(p + 1) = 12;

p[2] = 5

}

P

0x2f330000

0x2f330004

0x2f330008

0x2f0A0000

stack

heap

*p = *(p+0) = p[0]

*(p + n) = p[n]

54

new int [3];

= 0x2f330000

1

12

5

=

Pointer vs. Array

Array is a pointer pointed to itself

A pointer can point to an array addr.

int main()

{

char a[3] = {1, 2, 3, 4};

printf ("0x%x 0x%x %d\n", a, &a, *a);

int *p = new int[3];

p[0] = 1; p[1] = 2; p[2] = 3;

printf ("0x%x 0x%x %d\n", p, &p, *p);

int *p2 = (int*)a;

printf("value of p2 = 0x%x\n", *p2);

}

0x14fd64 0x14fd64 1

0x591398 0x14fd60 1

Value of p2 = 0x04030201

Command prompt

55

Pointer vs. Array

char a[3] = {1, 2, 3};

char *p = new char[3];

p[0] = 10; p[1] = 20; p[2] = 30;

printf ("a = 0x%x p = 0x%x\n", a, p);

printf ("a+1 = 0x%x p+1 = 0x%x\n", a+1, p+1);

printf ("&a = 0x%x &p = 0x%x\n", &a, &p);

printf ("&a+1= 0x%x &p+1 = 0x%x\n", &a+1, &p+1);

a = 0x26FE6C p = 0x0E1AF0

a+1 = 0x26FE6D p+1 = 0x0E1AF1

&a = 0x26FE6C &p = 0x26FE70

&a+1= 0x26FE6F &p+1 = 0x26FE74

Command prompt

10 20 30

1 a

0x0E1AF0

p

0x0E1AF1

0x0E1AF2

0x0E1AF3

0x0E1AF4

0x26FE70

0x26FE71

0x26FE72

0x26FE73

0x26FE74

0x26FE6C

2 0x26FE6D

3 0x26FE6E

0x26FE6F

&p + 1

&a + 1

56

a + 1

p + 1

Due to stack limited, can not create a too big array

Pointer vs. Array

int main()

{

char arr[1034996];

}

int main()

{


}

FAIL OK

0 Can not delete an array int main()

{

char arr[100];

delete arr;

}

int main()

{


delete p;

}

FAIL OK

Memory block of array is freed automatically when out-of-scope

Dynamic memory MUST be clean manually by call “delete” 57

Pointer vs. Array 2D array int arr[2][3]

pointer-to-pointer int **p = new int*[2];

p[0] = new int[3];

p[1] = new int[3];

[0][0] [0][1] [0][2]

[1][0] [1][1] [1][2]

p[1]

p[0] p p[0][0] p[0][1] p[0][2]

p[1][0] p[1][1] p[1][2]

0 2D array & 2D pointer could use in the same way

arr[2][2] = 5 p[2][2] = 10

58

[0][0] [0][1] [0][2] [1][0] [1][1] [1][2]

Block 0 Block 1

*(*(p + i) +j ) p[i][j]

C/C++ String

59

String

No standard string in C/C++

Use char*, or char[] instead

String in C/C++ is array of byte, end with ‘\0’

char *st = "String";

S t r i n g \0 st

60

String allocation

Static allocation


char st2[] = "String";

Dynamic allocation char *st3 = new char[6];

st3[0] = 's';

st3[1] = 't';

st3[2] = 'i';

st3[3] = 'n';

st3[4] = 'g';

st3[5] = '\0';

61

String allocation (cont.)

62

char* GetString1()

{


return st;

}

char* GetString2()

{

char st[] = "String";

return st;

}

char* GetString3()

{

char *st = new char[6];

strcpy(st, "String");

return st;

}

int main()

{

printf("Say: %s", GetString1());



}

What are different?

Memory utility functions

MUST #include <string.h>

void * memcpy ( void * destination, const void * source, size_t num )

Copies the values of num bytes from the location pointed by source directly to the memory block pointed by destination

int memcmp ( const void * ptr1, const void * ptr2, size_t num )

Compare the C string pointed by source into the array pointed by destination, including the terminating null character

63

Memory utility functions

size_t strlen ( const char * str )

• Returns the length of str • The length of a C string is determined by the terminating null-character • This should not be confused with the size of the array that holds the

string

char * strcpy ( char * destination, const char * source )

• Copies the C string pointed by source into the array pointed by destination, including the terminating null character

int strcmp ( const char * str1, const char * str2 )

• Compares the C string str1 to the C string str2.

http://www.cplusplus.com/reference/clibrary/cstring/ 64

http://www.cplusplus.com/reference/clibrary/cstring/

Constant pointer vs. pointer to constant

Constant pointer: • Address of memory stored is constant • Value at address which “pointed to” could be changed

65

Pointer to constant: • Value at address which “pointed to” is constant • Address of memory stored could be changed

char char_A = 'A';

const char * myPtr = &char_A;

*myPtr = 'J'; // error - can't change value of *myPtr

char char_A = 'A';

char char_B = 'B';

char * const myPtr = &char_A;

myPtr = &char_B; // error - can't change address of myPtr

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type



Function

Namespace

66

Enum

Use for set up collections of named integer constants

In traditional C way:

Alternate approach

#define SPRING 0

#define SUMMER 1

#define FALL 2

#define WINTER 3

enum {SPRING, SUMMER, FALL, WINTER};

0 1 2 3 67

Enum (cont.) Declaration

Values of enum constants

enum MyEnum {SPRING, SUMMER, FALL, WINTER};

enum MyEmum x; // C style

MyEnum y; // C++ style

int main()

{

y = MyEnum::SPRING;

y = FALL;

y = 1; // ILLEGAL

}

enum MyEnum {SPRING = 0, SUMMER = 10, FALL = 11, WINTER = 100};

int main()

{

y = MyEnum::SPRING;

printf("%d", y);

} 68

Union

Allow same portion of memory to be accessed as different data type

union MyUnion

{

int iValue;

char cValue;

char aValue[4];

};

int main()

{

MyUnion mine = {0x01020304};

printf("iValue: 0x%x\n", mine.iValue);

printf("iValue: 0x%x\n", mine.cValue);

printf("iValue: 0x%x 0x%x 0x%x 0x%x\n",

mine.aValue[0],

mine.aValue[1],

mine.aValue[2],

mine.aValue[3]);

}

0x04 0x03 0x02 0x01

iValue 0x01020304

0x04

0x04 0x03 0x02 0x01

cValue

aValue

Memory block

sizeof(mine) = ?

69

Struct

Define a structure type and/or a variable of a structure type.

struct T_MyStruct

{

int val1;

char val2;

char val3[5];

};

struct T_MyStruct myStruct;

val1

val2

val3

T_MyStruct

70

Struct

Using struct: typedef struct T_MyStruct

{

int val1;

char val2;

char val3[5];

}MyStruct;

MyStruct myStruct;

int main()

{

myStruct.val1 = 10;

myStruct.val2 = 100;

myStruct.val3[0] = 1000;

} 71

Data Structure alignment

Is the way data is arranged and accessed in computer memory.

Consist two issue:

• Data alignment:

oPut data at memory offset equal to multiple word size

• Structure padding:

o Insert some meaningless bytes between the of last data structure and start of next

72

Data Structure alignment

0 Before compile, total memory of T_MyStruct is 8 byte

struct T_MyStruct

{

char val1;

short val2;

int val3;

char val4;

};

• char: 1 byte aligned

• short: 2 byte aligned

• int : 4 byte aligned

• …

val1 val2 val3 val4

0 1 3 7

pad1

val2 val3 val4

0 1 2 3 4 8 9 10 11

val1

4 bytes block 4 bytes block 4 bytes block

pad2

4 bytes alignment

sizeof(T_MyStruct) == 12 bytes 73

VS Struct member alignment

74

GCC alignment

75

struct test_t

{

int a;

char b;

int c;

}__attribute__((aligned(8)));

struct test_t

{

int a;

char b;

int c;

}__attribute__((__packed__));

http://www.delorie.com/gnu/docs/gcc/gcc_62.html

8 byte alignment

smallest possible alignment

http://www.delorie.com/gnu/docs/gcc/gcc_62.html

Struct - function

C++ only, not available in C

Beside variable, struct also has had function

Struct alignment is not effected to struct-function

Function is not counted when calculate struct size

typedef struct T_MyStruct

{

int val1;

char val2;

char val3[12];

void SayHello();

}MyStruct;

void MyStruct::SayHello()

{

printf("Hello world");

}

int main()

{

MyStruct myStruct;

myStruct.SayHello();

}

76

Struct constructor / destructor

C++ only, not available in C

Two special function of struct

• Constructor: automatically call when a instant of struct is created

• Destructor: automatically call when a instant of struct is destroy


{

int val1;

T_MyStruct();

~T_MyStruct(); }MyStruct;

T_MyStruct::T_MyStruct()

{

printf("Created\n");

}

T_MyStruct::~T_MyStruct()

{

printf("Destroy\n");

}

int main()

{

MyStruct myStruct;

}

constructor

destructor

Created

Destroy

Command prompt

77

Struct and static member

Static function & static variable

Static variable is not counted is struct alignment and struct size


{

int val1;

static char val2;

static void SayHello() {}

}MyStruct;

int main()

{

MyStruct myStruct;

printf("%d", sizeof(myStruct));

MyStruct::SayHello();

}

78

Struct and Access privilege C++ only, not available in C Three access privilege methods

• public: visible for all • private: visible inside struct only • protected: visible inside struct and

retrieved struct (OOP)

• Default is public o For example: valx is public

79

struct MyStruct

{

int valx;

public:

int val1;

private:

int val2;

protected:

int val3;

};

int main()

{

MyStruct mine;

mine.val1 = 0;

mine.valx = 0;

mine.val2 = 0;

mine.val3 = 0;

}

Fatal Error, val2 is private

Fatal Error, val3 is protected

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type



Function

Namespace

80

C/C++ function

<return-type> function_name([<type> <param>], […])

void foo() {}

void foo(int a, int b, char c)

{}

int foo()

{

return 1;

}

No return function

Required return

81

Default parameters

#include <cstdio>

void foo(int a,

int b = 1 ,

int c = 2 );

void foo(int a, int b, int c)

printf("%d %d %d\n",

a, b, c);

}

void main()

{

foo(0);

foo(0, 10);

foo(0, 10, 100);

}

Set default value

Use b, c as default value

No default value

Use b, c as default value

0 1 2

0 10 2

0 10 100

Command prompt

82

void foo(int a, int b = 1, int c )

{

printf("%d %d %d\n", a, b, c);

}

Default parameters (cont.)

ERROR

error C2548: 'foo' : missing default parameter for parameter 3

When a parameter is set default value, the rest of next parameters MUST BE set default value too

RULES

83

Variable number of parameters

#include <cstdio>

#include <cstdarg>

int sum(int num_param, ... )

{

int sum = 0, val = 0;

va_list marker;

va_start(marker, num_param);

for (register int i = 0; i < num_param; i++)

{

val = va_arg(marker, int);

sum += val;

}

va_end(marker);

return sum;

}

void main()

{

printf("%d\n", sum(1, 10));

printf("%d\n", sum(3, 1, 2, 3));

} 84

Parameter classification

Value parameter

Reference parameter

Constant parameter

Const Reference parameter

Pointer parameter

85


Pass-by-value

A copy of parameter is made Value parameter

Reference parameter

Constant parameter


Pointer parameter

void foo(int n)

{

n++;

}

void main()

{

int x = 2;

foo(x);

printf("%d\n", x);

}

x = 2

2 x 2 x

2 n

2 x

3 n 2 x

foo 86


Pass-by-reference Actually parameter itself is passed Use reference operator “&”

Value parameter

Reference parameter

Constant parameter


Pointer parameter

void foo(int &n)

{

n++;

}

void main()

{

int x = 2;

foo(x);

printf("%d\n", x);

}

x = 3

2 x 2 x

n

x 3

n 3 x

foo 87


Pass-by-value A copy of parameter is made and

strict as const.

Value parameter

Reference parameter

Constant parameter


Pointer parameter

void foo(int cont n)

{

n++;

}

void main()

{

int x = 2;

foo(x);

printf("%d\n", x);

}

Fail, can not modified

const value

2 x 2 x

2 n

2 x

3 n

foo 88


Pass-by-ref

Actually parameter itself is passed but avoid modify

Void the overhead of creating a copy

Value parameter

Reference parameter

Constant parameter


Pointer parameter

void foo(int const &n)

{

//todo

}

89


In common, Pass-by-value

A copy of parameter is made Value of parameter is an address of a memory block

Value parameter

Reference parameter

Constant parameter


Pointer parameter

void foo(int *n)

{

//todo

}

Value of parameter will not be change,

but memory block which pointed by parameter could be modified.

90

Pointer Parameter

#include <cstdio>

void foo(int *A, int *B)

{

int *tmp = A;

A = B;

B = tmp;

}

void main()

{

int A[] = {1, 2, 3};

int B[] = {10, 11};

printf("0x%x 0x%x\n", A, B);

foo(A, B);


}

A’

B’

A’

B’

A

B

A

B

Copy value (addr. of data)

foo

0x29faa8 0x29faa0

0x29faa8 0x29faa0

Command prompt

91

Pointer Parameter

#include <cstdio>

void foo(int *A)

{

A[2] = 10;

}

void main()

{

int A[] = {1, 2, 3};

printf(“%d\n", A[2]);

foo(A);

printf(“%d\n", A[2]);

}

A’

A

foo 1

2

3 A’[2] = 10 10

A

A[2] = 3

A[2] = 10

Copy value (addr. of data)

92

Pointer reference parameter

A special case of pointer parameter Value of pointer parameter (address of block memory) could be changed Pass-by-reference CAN NOT work with array directly

#include <cstdio>

void foo(int *&A, int *&B)

{

int *tmp = A; A = B; B = tmp;

}

void main()

{

int arr1[] = {1, 2, 3};

int arr2[] = {10, 11};

int *A = arr1;

int *B = arr2;


foo(A, B);


}

A

B

A

B

A

B

A

B

foo

0x31fc90 0x31fc88

0x31fc88 0x31fc90

Command prompt

93

Function overloading

C++ only

Allow multiple functions with the same name, so long as they have different parameters.

void Todo(int a)

{}

void Todo(int a, int b)

{}

94

Function Prototype

In C/C++, functions MUST BE declare before using. To solve this problems

• Keep all functions in correct order • Use prototype inside .cpp file • Use prototype inside header (.h) file -> recommend

#include "header.h"

void Todo1()

{

Todo2();

}

void Todo2(){}

int main(){}

Main.cpp

void Todo1()

{

Todo2();

}

void Todo2()

{}

int main()

{}

Error error C3861: 'Todo2': identifier not found

Main.cpp header.h

void Todo1();

void Todo2();

95

Extern function

Sometimes, we need to use a function in another module (.cpp file)

Header file is too complicated to use (caused error when used)

#include <cstdio>

extern void TodoExtern();

int main()

{

TodoExtern();

return 1;

}

Main.cpp

#include <cstdio>

void TodoExtern()

{

printf("TodoExtern\n");

}

Extern.cpp

96

Extern “C”

Name mangling: • Aka “name decoration”

• The way of encoding additional information in a name of function, struct, class…

In C++: • For adapting overload, class/struct functions, name of

function will be “encoding”

int f (void) { return 1; }

int f (int) { return 0; }

int __f_v (void) { return 1; }

int __f_i (int) { return 0; } 97

Extern “C”

For mixing “C” and “C++” source (Object C also) use extern "C"

Extern “C” talk to compiler that use C style for its scope • No “name mangling” • No overloading

Extern “C” is also “extern” function could be implement in another module

#include <stdio.h>

void ExternC()

{

printf("ExternC\n");

}

Ansi_c.c extern "C"

{

void ExternC();

void Todo()

{

printf("%d", i);

}

}

C_plusplus.cpp

98

Extern “C” in practice

#ifdef __cplusplus

extern "C" {

#endif

// your code here

#ifdef __cplusplus

}

#endif

__cplusplus: default C++ preprocessor definition

99

Pointer to function

A variable store address of a function

Advantage

• Flexible

• User for event handling mechanism

// C

void DoIt (float a, char b, char c){……}

void (*pt2Function)(float, char, char) = DoIt;

// using

pt2Function(0, 0, 0);

100

Inline function

Macro: preprocessor replaces all macro calls directly with the macro code

101

#define NEXT(a) (a+1)

int main()

{

printf("%d", NEXT(1));

}

int main()

{

printf("%d", (a + 1));

}

Inline function (cont)

Like macro, but obeys C/C++ syntax

102

inline int Next(int x)

{

return x + 1;

}

int main()

{

printf("%d", Next(1));

}

For OOP, Inline function is allowed to set access privilege

Improve performance (for short/simple inline functions)

NOTE: The compiler is not forced to inline anything at all

Why performance is

improved?

Outline

Preparation

Getting Start

OOP

Memory management



Primary data type



Function

Namespace

103

Namespace

A abstract container uses for grouping source code.

In C++, a namespace is defined with a namespace block

namespace maths {

void sin() {}

void cos() {}

void add() {}

}

namespace matrix {

void mult() {}

void add() {}

}

104

Using namespace

For using methods, variables, … of a namespace:

<namespace>::<methods/variables>

namespace maths {

void sin() {}

void cos() {}

void add() {}

}

namespace matrix {

void mult() {}

void add() {}

}

void main()

{

maths::sin();

matrix::add();

} 105

Using namespace

Use using namespace for shorten way.

namespace maths {

void sin() {}

void cos() {}

void add() {}

}

namespace matrix {

void mult() {}

void add() {}

}

using namespace maths;

using namespace matrix;

void main()

{

sin();

mult();

}

106

Namespace – ambiguous call

More than two definition of add functions

• maths::add()

• matrix::add()

ambiguous call fatal error.

In this case, MUST BE specify namespace.

namespace maths

{

void add();

}

namespace matrix

{

void add();

}

using namespace maths;

using namespace matrix;

void main()

{

add();

}

error C2668: 'matrix::add' : ambiguous call to overloaded function .\main.cpp(8): could be 'void matrix::add(void)' .\main.cpp(3): or 'void maths::add(void)'

107

Outline

Preparation

Getting Start

OOP

Memory management


Class & Object

Inheritance

Polymorphism



Outline

Preparation

Getting Start

OOP

Memory management


Class & Object

Inheritance

Polymorphism



Class As same as struct Default access is private

110

class MyClass

{

public:

MyClass();

~MyClass();

protected:

int GetVal() {return m_Var;}

void Todo();

private:

int m_Var;

void SayHello();

};

void MyClass::Todo()

{

//some code here

}

Class name

Access methods

Constructor

Destructor

Function (methods)

Inline methods

Class variable (property)

Function implementation

Class (cont)

In traditional, code of class is divided into 2 parts

• Declaration: in .h file

• Implementation: in .cpp file

111

#ifndef __CCLASS_H__

#define __CCLASS_H__

class CClass

{

public:

CClass();

~CClass();

private:

void Toso() ;

};

#endif

Any_name.h #include "Any_name.h" void CClass::Todo()

{

…

}

CClass::~CClass()

{

…

}

Any_name.cpp

How to use class

112

MyClass objA; //or MyClass objA()

objA.SayHello();

• Create a object directly • Access class methods,

properties by using dot

• Create a object through pointer. • Two ways to use methods,

properties o (*objA). C style o objA-> C++ style

• Supported polymorphism

MyClass *ObjB = new MyClass;

//or MyClass *ObjB = new MyClass();

(*objA).SayHello();

objA->SayHello();

Recommend!

MyClass *ObjB = new MyClass;

objA->SayHello();

Access methods

Aka Encapsulation

• Public: allow access inside & outside class

• Protected: allow access inside class & in derived class

• Private : allow access inside class only

113

http://en.wikipedia.org/wiki/Encapsulation_(object-oriented_programming)

Constructor

Should be public

Called when an instance is created

A class could define a set of constructors (constructor overloading)

114

class MyClass

{

public:

MyClass();

MyClass(MyClass* A);

MyClass(const MyClass& A);

MyClass(int val);

}

Default constructor

Copy constructor.

Copy constructor

Definition:

• A constructor with the same name as the class

• Used to make a deep copy of objects (be careful if class content pointer properties)

115

If no user-defined constructor is defined, compiler defines one.

X (const X& copy_from_me)

X (X* copy_from_me)

X (X& copy_from_me)

X (const X&copy_from_me, int = 10, float = 1.0 )

Must be set default value

Copy constructor (cont.)

Invoked when

• When a object is created from another object of the same type

• When an object is passed by value as parameter to function

• When a object is return from a function

116

class ABC

{

public:

ABC(){}

ABC(ABC *A){printf("here1\n");}

ABC(const ABC &A)

{

printf("here2\n");

}

};

void Foo1(ABC A){}

ABC Foo2()

{

ABC a;

return a;

}

int main()

{

ABC *A = new ABC();

ABC B(A);

Foo1(A);

Foo2();

}

Copy constructor (cont)

A default copy constructor is created automatically, but it is often not what you want.

117

Image(Image *img) {

width = img->width;

height = img->height;

data = new int[width*height];

for (int i=0; i<width*height; i++)

data[i] = img->data[i];

}

Image(Image *img) {

width = img->width;

height = img->height;

data = img->data;

}

Automatic generated copy constructor User-defined (expected) copy contructor

Explicit constructor

"nonconverting" Explicit constructor syntax is required.

118

class A {

public:

explicit A(int) {}

};

void f(A) {}

void g()

{

A a1 = 37;

A a2 = A(47);

a1 = 67;

f(77);

}

Without explicit With explicit

Destructor

Automatically invoked when an object is destroy: • Out of scope • Or manually free (use

pointer)

Use for collect class memory

119

class MyClass

{

char m_Var;

int m_pData;

public:

MyClass(char id) {

m_Var = id;

m_pData = new int[100];

};

~MyClass() {

delete m_pData;

cout<<"Destroyed "<<m_Var<<endl;

}

};

int main()

{

cout << "---Alloc A---"<<endl;

MyClass *A = new MyClass('A');

cout << "---Free A---"<<endl;

delete A;

cout << "---Create B---"<<endl;

MyClass B('B');

cout << "---End---"<<endl;

return 1;

}

---Alloc A---

---Free A---

Destroyed A

---Create B---

---End---

Destroyed B

Command prompt

“this” pointer

A special pointer point to class instance itself

Used inside class, for access class methods, properties

120

class MyClass

{

char m_Var;

public:

MyClass(char id) {m_Var = id;};

~MyClass() {}

MyClass* Todo1(int val)

{

if (this->m_Var == val)

{

return this;

}

return 0;

}

void Todo2()

{

this->Todo1('A');

}

};

Member initialization

121

class MyClass

{

private:

int m_iVar1;

float m_fVar2;

char * m_pVar3;

public:

MyClass();

}

MyClass::MyClass():

m_iVar1(10),

m_fVar2(1.3f),

m_pVar3(0)

{

}

Setup value of properties

Outline

Preparation

Getting Start

OOP

Memory management


Class & Object

Inheritance

Polymorphism



Inheritance

Code reuse:

• Composition: create objects of existing class inside the new class

• Inheritance: create a new class as a type of an existing class

123

Existing class

New class

class NewClass

{

public:

ExistingClass *m_member;

};

Base class

Derive class Hierarchy model

class Derive: public Base

{

};

Inheritance syntax

124


{

public:

Derive():Base() {}

void Todo();

};

void Derive::Todo()

{

this->protectedFunc();

this->publicFunc();

this->privateFunc();

Base::Todo();

}

class Base

{

public:

Base() {}

void publicFunc() {}

void Todo() {}

protected:

void protectedFunc() {}

private:

void privateFunc() {}

};

FAIL: cannot access private member

Access base’s method (same name)

Constructor init

Inheritance access

Base access Inherit access Derive access

Public

Public

Public

Protected Protected

Private Private

Public

Protected

Protected

Protected Private

Private

Public

Private private Protected

Private

125

Inheritance access Example

126

class CAnimal

{

public:

void Drink();

protected:

void Run();

private:

void Eat();

};

class CRabbit: private CAnimal

{

public:

CRabbit()

{

Run();

Eat();

Drink();

}

};

void main()

{

CRabbit rab;

rab.Drink();

rab.Eat();

rab.Run();

} Why?

Constructor – Destructor – Inheritance

127

Animal

Mammal

Lion

Lion *theLion = new Lion()

Lion()

Animal()

Mammal()

delete theLion;

~Lion()

~Mammal()

~Animal()

Multiple inheritance A class could be inherit from multiple base class

128

Human

StreetMusician

Musician Worker

class Human{};

class Musician

{

public:

Musician(int instrument, int year){}

};

class Worker

{

public:

Base2(int level){}

};

class StreetMusician: public Human,

protected Musician,

private Worker

{

public:

StreetMusician(): Human(),

Musician(1, 1),

Worker(10) {}

};

Inheritance Ambiguous access

CBase1::Hello() CBase2::Hello()

129

class CBase1

{

public:

void Hello();

};

class CBase2

{

public:

void Hello();

};

class CDerive: CBase1, CBase2

{

public:

CDerive(): CBase1(), CBase2()

{

Hello();

}

};

Ambiguous access of 'Hello‘

How to solve?

Outline

Preparation

Getting Start

OOP

Memory management


Class & Object

Inheritance

Polymorphism



Polymorphism

Implemented in C++ with virtual functions

• Virtual function

• Pure virtual function

• Pure virtual class (abstract class / base class)

Use for improved code organization

Extensible

131

Function call binding

Binding:

• Connecting a function call to a function body

Early binding:

• Binding is performed before the program is run by compiler, linker

Late binding:

• Binding occurs at runtime, based on the type of the object

• Aka Dynamic binding or Runtime binding

For C++, to cause late binding, use keyword “virtual”

132

Overriding vs. Overloading

Overriding: override a base’s virtual or non-virtual methods

Overloading: several methods with the same name which differ from parameters

133

class Animal

{

public:

virtual void Eat(){}

void Run(){}

};

class Cat: public Animal

{

public:

//overiding

void Eat(){}

void Run(){}

//overloading

void Jump();

void Jump(int distance);

};

Virtual Overriding vs. non-virtual Overriding

Obj is a Animal pointer, but really a Cat instant

Without virtual (early binding), Animal:Run was called instead of Cat::Run

134

class Animal

{

public:

virtual void Eat()

{

cout<<“Animal:Eat"<<endl;

}

void Run()

{

cout<<“Animal:Run"<<endl;

}

};

class Cat: public Animal

{

public:

void Eat()

{

cout<<“Cat:Eat"<<endl;

}

void Run()

{

cout<<“Cat:Run"<<endl;

}

};

int main()

{

Animal *obj = new Cat();

obj->Eat();

obj->Run();

}

Cat:Eat

Animal:Run

Command prompt

Virtual destructor

When obj is freed, both itself and base MUST BE deleted

It’s ok for obj1, but problem for obj2

135

class Base

{

public:

~Base()

{

cout<<"Destroy Base"<<endl;

}

};


{

public:

~Derive()

{

cout<<"Destroy Derive"<<endl;

}

};

int main()

{

Derive *obj1 = new Derive();

Base *obj2 = new Derive();

cout<<"--Free obj1--"<<endl;

delete obj1;


delete obj2;

}

--Free obj1--

Destroy Derive

Destroy Base

--Free obj2--

Destroy Base

Command prompt

Virtual destructor (cont)

To solve this problem, use virtual destructor

136

class Base

{

public:

~Base()

{

cout<<"Destroy Base"<<endl;

}

};


{

public:

~Derive()

{

cout<<"Destroy Derive"<<endl;

}

};

int main()

{

Derive *obj1 = new Derive();

Base *obj2 = new Derive();


delete obj1;


delete obj2;

}

virtual

--Free obj1--

Destroy Derive

Destroy Base

--Free obj2—

Destroy Derive

Destroy Base

Command prompt

Pure virtual function Pure virtual class

Pure virtual function:

• Virtual function with no body

Pure virtual class:

• Class content pure virtual function

CAN NOT create an instance of pure virtual class directly

Derive class of pure virtual class MUST implements all pure virtual functions

137

class Base

{

public:

virtual void Todo() = 0;

};


{

void Todo() {}

}

Outline

Preparation

Getting Start

OOP

Memory management


Class & Object

Inheritance

Polymorphism




Another way to make a function call

Define function of operator such as : +, -, *, /, …

WARNING: Not recommend to use. It’s easy to read, but hard to debug !

139

Operator overloading example

140

class Integer

{

public:

int i;

Integer(int ii) : i(ii) {}

const Integer operator+(const Integer& rv)

{

return Integer(i - rv.i);

}

Integer& operator+=(const Integer& rv)

{

i *= rv.i;

return *this;

}

};

int main()

{

Integer ii(1), jj(2), kk(3);

kk += ii + jj;

cout << "Value = " << kk.i << endl;

}

This implementation make user confused

Outline

Preparation

Getting Start

OOP

Memory management


Class & Object

Inheritance

Polymorphism



Static function

Allow user invokes without creating an instance

Declaration with static keyword

No need to create object, but must be declared class name

142

class MyClass

{

public:

static void Todo();

};

void MyClass::Todo()

{

//implemetation

}

int main()

{

MyClass::Todo();

}

Static variable

Same as static function

Value of static variable MUST BE set outside class declaration.

143

class MyClass {

public:

static int s_Var;

};

int MyClass::s_Var = 99;

int main()

{

printf("%d",

MyClass::s_Var);

}

Lazy initialization

0 The tactic of delaying the creation of an object, calculation of a value, or some other expensive process until the first time it is need.

144

class ExpensiveRes

{

public:

ExpensiveRes() {}

void todo1();

static ExpensiveRes* GetInstance();

private:

static ExpensiveRes* s_Instance;

};

ExpensiveRes* ExpensiveRes::s_Instance = 0;

ExpensiveRes* ExpensiveRes::GetInstance()

{

if (!s_Instance)

{

s_Instance = new ExpensiveRes();

}

return s_Instance;

}

int main()

{

ExpensiveRes::GetInstance()->todo1();

ExpensiveRes::GetInstance()->todo1();

}

Outline

Preparation

Getting Start

OOP

Memory management


Recall pointer

Memory leak

145

Question?

What does “memory leak” mean ?

• How is memory structure ?

What does its consequences ?

Why does “memory leak” happen ?

How to detect and solve?

146

What does “memory leak” mean ?

First, How is memory structure ?

147

How is memory structure ? STACK vs HEAP

148

Run-time storage

Code segment: • where the compiled program sits in

memory

Global area: • store global variables

Stack segment: • where parameters and local variables are

allocated

Heap segment: • where dynamically allocated variables are

allocated

149

Text segment (Code segment)

Stack segment

Heap Segment

Global area

Stack

Where parameters and local variables are allocated

Limited size Stack overflow

Memory use in stack is temporary and auto release

Fast processing/low size

150

Parameters

Return Address where to begin execution

when function exits

Dynamic link pointer to caller's stack

frame

Static link pointer to lexical parent

(for nested functions)

Return value

Local variables

“Concept” Stack frame


Stack frame

Heap Segment

Global area

Stack frame

Heap

Large pool of memory

Dynamic allocation

Stays allocated until specifically deallocated leak !

Must be accessed through a pointer

Large arrays, structures, or classes should be stored Heap why?

Large & dynamic

151

Parameters

Return Address where to begin execution

when function exits

Dynamic link pointer to caller's stack

frame

Static link pointer to lexical parent

(for nested functions)

Return value

Local variables

“Concept” Stack frame


Stack frame

Heap Segment

Global area

Stack frame

Heap vs Stack

int _array[10]; stored in stack

152

Stack

_array int *_array = new int[n]

• Pointer _array is stored in Stack

• Data of array is stored in Heap

_array 0x00FF

Stack

10

Heap

0x00FF

0x0005

Value of: ● _array : address where int “point” into in heap (0x00FF) ● (*_array): value at it's address on heap (10) ● (&_array): address of the memory which used for stored pointer _array in stack (0x0005)

FAQ

Why we use

• Classname *Obj = new Classname();

instead of

• Classname Obj;

153

Memory leak overview

154

What does memory leaking mean?

Definition: • Particular type of unused memory, unable to release

Common: • Refer to any unwanted increase in memory usage

* usually for heap memory

155

void Leak()

{

int *A = new int[1000];

// some code here

// ...

// without delete A

//

return;

}

4000 bytes

Return without free A → Leak

What does its consequences ?

Application gets slow fps

Application is crashed

Device has been freeze, restarted

156

Why does “memory leak” happen?

First, Let's see some examples

157

Example 0 Forget to release resources

– No GC mechanic supported

Button is pressed

Save current floor

On target floor ?

Wait until lift is idle

Go to required floor

Release memory used to save current floor

True

Finished Memory

Leaking here

158

C/C++ Example 1

● Leak memory caused by lacking of release dynamic memory

…

delete a[];

return;

Solution

Leak !

159

C/C++ Example 2

void leak()

{

int **list = new int*[10];

for (int i = 0; i < 10; i++)

{

list[i] = new int;

}

delete list;

return;

}

Allocation a series, delete only one unit

Leak ! for (int i = 0; i < 10; i++)

{

delete list[i];

}

delete list;

Solution

160

C/C++ Example 3

Leak memory when using pointer-return-type

delete []str;

Avoid to call directly GenString()

Solution

161

char* GenString()

{

char *a = new char[10];

a[9] = '\0';

return a;

}

void Leak()

{

char *str = GenString();

printf("%s\n", str);

printf("%s\n", GenString());

}

C/C++ Example 4 Leak memory when using pointer as a

parameter

Stack

Heap

A

LEAK!

Leak!

Well control with reference variables Check if a pointer is allocated memory yet!

Solution

162

C/C++ Example 5

void main()

{

Classname *A = new A();

...

...

//free A

A = NULL;

}

163

Misunderstand free memory method in C/C++

Stack

Heap

A

NULL

LEAK!

Keep in mind we are using C/C++ Use MACRO for safe deallocating #define SAFE_DEL(a) {if(a){delele a;a = 0;}}

Solution

Example 6

164

class CB {

public:

CB(){

m_iVal = 0;

}

~CB(){}

int m_iVal;

};

class CA {

public:

CA(){

m_pB = 0;

}

~CA(){

delete m_pB;

m_pB = 0;

}

CB *m_pB;

};

int main()

{

CB *B = new CB;

CA *A = new CA();

A->m_pB = B;

delete(A);

printf("%d", B->m_iVal);

}

B

A m_pB

Access violation reading location

….

Try to remove

delete m_pB

Example 6 (cont.)

165

class CB {

public:

CB(){

m_iVal = 0;

}

~CB(){}

int m_iVal;

};

class CA {

public:

CA(){

m_pB = 0;

}

~CA(){

delete m_pB;

m_pB = 0;

}

CB *m_pB;

};

int main()

{

CA *A = new CA();

A->m_pB = new CB()

delete(A);

}

A m_pB

Leak

Delete or not?

Use manual delocate m_pB

Solution

C/C++ Example 7 class cA()

{

public :

cA() {m_pdata = new int[100];}

virtual ~cA() {delete[] m_pdata;}

int *m_pdata;

};

class cB: public cA()

{

public

cB():cA() {m_pdata2 = new int[100];}

~cB() {delete []m_pdata2;}

int *m_pdata2;

}

void main()

{

cA *A = new cB();

delete A;

}

● Memory leak caused by

misunderstanding finalization

method

Without “virtual”, in this case, m_pdata is not deleted → leak

Be careful with “virtual” for

finalization method

Solution

166

What are reasons of memory leak?

Forget/ misunderstand C/C++ mechanism

Out-of-Control (logic)

167

Current Solutions

For “Forget/ misunderstand C/C++ mechanism”

• Semi-automatic memory management

oReference Counting

• Automatic memory management

oTracing Garbage Collection (GC): Java , C #

No GC mechanic for C/C++

168

Current Solutions - Disadvantage

Garbage collectors generally can do nothing about logical memory leaks

169

0

1

2

n

..

.

Alloc

Alloc

Alloc

Alloc

Which is really needed? A

B

D

E

Z

Do I alloc some- where without

release?

Somethings else is pointed

to an object

C/C++ How to avoid, detect?

Rule:

• Remember to release dynamic data (pointer)

• Keep our resource in well controlled

Detect

• By phenomenon on device ? not exactly

• By review source ? too hard

• By tool

oVC++ memory leak debugging

oExternal tool

170

Too hard

C/C++ How to solve?

Depend on kind of memory leak

Experience: Improve C/C++ skill

Organize source and keep it in control

• Such as a document about resource ?!?

171

Detect Memory Leak

172

Debug in Visual studio

173

VLD Tool 0 http://www.codeproject.com/KB/applications/visualleakdetector.aspx

174

http://www.codeproject.com/KB/applications/visualleakdetector.aspx

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 175

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

Bit processing

STL introduction

GNU GCC/G++ 176

Forward declaration

Declaration of a identifier which not completed definition

For C/C++, aka function prototype (for function)

177

int first(int x) {

if (x == 0)

return 1;

return second(x-1);

}

int second(int x) {

if (x == 0)

return 0;

return first(x-1);

}

int second(int x);

int first(int x) {

if (x == 0)

return 1;

return second(x-1);

}

int second(int x) {

if (x == 0)

return 0;

return first(x-1);

}

Forward declaration

178

ClassA.h ClassB.h

#ifndef _CLASSA_H_

#define _CLASSA_H_

class ClassA

{

public:

ClassA();

ClassB* m_pB;

};

#endif

#ifndef _CLASSB_H_

#define _CLASSB_H_

class ClassB

{

public:

ClassB();

ClassA* m_pA;

};

#endif

ClassA.cpp ClassB.cpp

#include "ClassA.h"

ClassA::ClassA(){}

#include "ClassB.h"

ClassB::ClassB(){}

Class forward declaration

#include "ClassB.h" #include "ClassA.h"

class ClassB; class ClassA;

Must be pointer

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

Bit processing

STL introduction

GNU GCC/G++ 179

Standard IO

stdio.h

int printf ( const char * format, ... );

• Format: %[flags][width][.precision][length]specifier

• Write data to stdout and store

180

printf ("Characters: %c %c \n", 'a', 65);

printf ("Decimals: %d %ld\n", 1977, 650000L);

printf ("Preceding with blanks: %10d \n", 1977);

printf ("Preceding with zeros: %010d \n", 1977);

printf ("Some different radixes: %d %x %o %#x %#o \n", 100, 100, 100, 100, 100);

printf ("floats: %4.2f %+.0e %E \n", 3.1416, 3.1416, 3.1416);

printf ("Width trick: %*d \n", 5, 10);

printf ("%s \n", "A string");

Standard IO

stdio.h

int scanf( const char * format, ... );

• Format: %[flags][width][.precision][length]specifier

• Reads data from stdin and store

181

int n;

scanf ("%d",&n);

Standard IO

<iostream>

std::cout

• an object of class ostream that represents the standard output stream

182

cout << "Hello there.\n";

cout << "Here is 5: " << 5 << "\n";

cout << "The manipulator endl writes a new line to the screen." << endl;

cout << "Here is a very big number:\t" << 70000 << endl;

cout << "Here is the sum of 8 and 5:\t" << 8+5 << endl;

cout << "Here's a fraction:\t\t" << (float) 5/8 << endl;

cout << "And a very very big number:\t" << (double) 7000 * 7000 << endl;

cout << "I am a C++ programmer!\n";

Standard IO

0 <iostream>

std::cin

• an object of class istream that represents the standard input stream

183

int input = 0;

cout << "Enter a number here: ";

cin >> input;

cout << "You entered the number " << input << ".\n";

File <stdio.h>

184

FILE * fopen ( const char * filename, const char * mode ); Open file

int fclose ( FILE * stream ); Close a file

size_t fwrite ( const void * ptr, size_t size, size_t count,

FILE * stream );

Write block of data to stream

size_t fread ( void * ptr, size_t size, size_t count, FILE *

stream );

Read a block data from stream

int fscanf ( FILE * stream, const char * format, ... ); Read formatted data from stream

int fprintf ( FILE * stream, const char * format, ... ); Write formatted output to stream

int fseek ( FILE * stream, long int offset, int origin ); Reposition stream position indicator Origin: • SEEK_SET : beginning of gfile • SEEK_END: end of file • SEEK_CUR: current position

long int ftell ( FILE * stream ); Get current position in stream

void rewind ( FILE * stream ); Set position indicator to the beginning

http://www.cplusplus.com/reference/clibrary/cstdio/fopen/

File <stdio.h>

185

#include <stdio.h>

int main ()

{

FILE * pFile;

pFile = fopen ("myfile.txt","w");

if (pFile!=NULL)

{

fprintf (pFile, "example");

fclose (pFile);

}

return 0;

}

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 186

Function template

special functions that can operate with generic types

Can be adapted to more than one type or class without repeating code

A set of needed functions will be created when compile slow down compiling process

187

template <class identifier> function_declaration;

template <typename identifier> function_declaration;

Function template Example 1

188

template <class T> T GetMax (T a, T b)

{

return (a>b?a:b);

}

int main ()

{

int i=5, j=6, k;

long l=10, m=5, n;

k=GetMax<int>(i,j);

n=GetMax<long>(l,m);

cout << k << endl;

cout << n << endl;

return 0;

}

Function template Example 2

189

template <class U, class V> U GetMax (U a, V b)

{

return (a>b?a:b);

}

int main()

{

cout << GetMax<float, int>(10.5, 12.5) <<endl;

cout << GetMax<float>(10.5, 12.5) <<endl;

return 1;

}

Class template

A class can have members that use template parameters as types

190

template <class T>

class mypair

{

T values [2];

public:

mypair (T first, T second)

{

values[0]=first; values[1]=second;

}

};

int main()

{

return 1;

mypair<int> Pair1(100, 200);

mypair<char> Pair2('A', 'B');

}

template <class T> class mypair

{

T a, b;

public:

mypair (T first, T second) {a=first; b=second;}

T getmax ();

};

template <class T> T mypair<T>::getmax ()

{

T retval;

retval = a>b? a : b;

return retval;

}

int main ()

{

mypair <int> myobject (100, 75);

cout << myobject.getmax();

return 0;

}

Class template

Function member outside the declaration of the class template, we must always precede that definition with the template <...> prefix

191

Template prefix

Return type

Class prefix

Class template. Template specialization

Define a different implementation for a template when a specific type is passed as template parameter

192

// class template:

template <class T>

class mycontainer

{

T element;

public:

mycontainer (T arg)

{

element=arg;

}

T increase () {return ++element;}

};

// class template specialization:

template <>

class mycontainer <char>

{

char element;

public:

mycontainer (char arg)

{

element=arg;

}

char uppercase ()

{

if ((element>='a')&&(element<='z'))

element+='A'-'a';

return element;

}

};

Class template

New code will be generated while compiling, DO NOT split a template class into two parts: .h, and .cpp

Easy to use, but not easy to debug/read

193

Mixin

We can implement inheritance delaying the definition of the base.

194

template <class Base>

class Mixin : public Base {};

class Base {};

Mixin issue

If the client never calls Todo there is no error message!

195

template <class Base>

class Mixin : public Base

{

public:

void Todo() {Base::Do();}

};

class Base

{};

C++ meta programming

Is writing programs that represent and manipulate other programs (e.g. compilers, program generators, interpreters) or themselves (reflection).

In C++, meta programming base on: Template

196

Example: Factorial

N! = 1 x 2 x 3 x … x N

197

template<int n> struct Factorial

{

enum {RET=Factorial<n-1>::RET*n};

};

// Note: template specialization

template<> struct Factorial<0>

{

enum{RET=1};

};

int main()

{

printf("%d", Factorial<10>::RET);

return 1;

}

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 198

Type casting

0 Convert from specific type to another type

char a = 10;

int b = (int) a;

bool c = a;

float d = float(a);

Explicit casting c-like casting notation

Implicit casting

Explicit casting Functional notation

199

Numeric overflow

void main()

{

int a = 200;

char c = a;

}

c = -56 ?

200

Float to int casting

void main()

{

float f = 2.7;

int i = f;

}

i is equal

to or ?

201

Bool & bool casting

Bool have two values:

• True

• False

In C/C++:

• False is zero

• True is non-zero

void main()

{

int i = 10;

bool b = i;

bool c = !i;

}

b = true

c = false

202

C++ type casting

Beside basic implicit and explicit type casting, C++ also supported:

• dynamic_cast<>

• static_cast<>

• const_cast<>

• reinterpret_cast<>

203

const_cast<>

Used to add to or remove the const-ness or volatile-ness of the expression

204

struct One

{

void funct1() { cout<<"Testing..."<<endl;}

} ;

void funct2(const One& c)

{

//will generate warning/error, if without const_cast

One &noconst = const_cast<One&> (c);

noconst.funct1();

}

void main()

{

One b;

funct2(b);

}

reinterpret_cast<>

Allows any integral type to be converted into any pointer type and vice versa

Can be used for conversions such as char* to int*, or One_class* to Unrelated_class*, which are inherently unsafe.

Can not cast away the const, volatile

205

reinterpret_cast<> Example

206

// Returns a hash code based on an address

unsigned short Hash( void *p )

{

unsigned int val = reinterpret_cast<unsigned int>( p );

return ( unsigned short )( val ^ (val >> 16));

}

int main()

{

int a[20];

for ( int i = 0; i < 20; i++ )

cout << Hash( a + i ) << endl;

}

static_cast<>

0 Allows casting 0 a pointer of a derived class to its base class and vice versa 0 int to enum 0 Reference of type &p to &q 0 Object type P to Object type Q 0 Pointer to a member to pointer to a member with the same hierarchy. 0 Any expression to void 0 Primary data type

0 This cast type uses information available at compile time to perform the required type conversion

0 No runtime safety check

207

static_cast<>

208

#include <iostream.h>

#include <stdlib.h>

enum color {blue, yellow, red, green, magenta};

int main()

{

int p1 = 3;

cout<<"integer type, p1 = "<<p1<<endl;

cout<<"color c1 = static_cast<color> (p1)"<<endl;

color c1 = static_cast<color> (p1);

cout<<"enum type, c1 = "<<c1<<endl;

return 0;

}

integer type, p1 = 3

color c1 = static_cast<color> (p1)

enum type, c1 = 3

Press any key to continue . . .

Command prompt

dynamic_cast<>

209

Enable Run-Time Type Info first

dynamic_cast<>

Used with pointers and references to objects for class hierarchy navigation

Requires the Run-Time Type Information (RTTI)

If the pointer being cast is not a pointer to a valid complete object of the requested type, the value returned is a NULL pointer

Used for polymorphism class

210

dynamic_cast<>

Type conversion from base class pointer to a derived class pointer is called downcast.

Type conversion from derived class pointer to a base class pointer, is called upcast.

From a class to a sibling class in class hierarchy: crosscast

211

Class Base

Class Derive1

Class Derive2

Base

Derive1

Derive2

downcast

upcast

dynamic_cast<> upcast

Always successful

212

Base

Derive1

Derive2

Why?

Derive class always “contents” valid complete base class

dynamic_cast<> upcast – multiple conversion with

multiple inheritace

CAN NOT cast directly from Derived3 to base.

Do step by step:

• Derived3 Derived2 Base

• Or Derived3 Derived1 Base

213

Base

Derived 1 Derived 2

Derived 3

dynamic_cast<> downcast

Available for polymorphism class only

214

Base

Derive

Funct2()

Funct3() class Base1 {

public:

virtual void funct1(){};

};

class Derived1:public Base1 {

public:

virtual void funct2(){};

};

dynamic_cast<> downcast (cont.)

215

Base

Derive

Funct2()

Funct3()

Base* Test1 = new Derived;

Base* Test2 = new Base;

Test1

Test2

Derived* Test3 = dynamic_cast<Derived*>(Test1);

Derived* Test4 = dynamic_cast<Derived*>(Test2);

successful

fail

dynamic_cast<> crosscast

Crosscast Base2 Derived1

216

Base2 Base

Derived 1 Derived 2

Derived 3

Base2 *p1 = new Derived3;

Derived1 *p2 = dynamic_cast<Derived1*>(p1);

Base2 *p1 = new Base2;

Derived1 *p2 = dynamic_cast<Derived1*>(p1);

Fail

OK

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 217

Exception Handling

Improved error recovery is one of the most powerful ways you can increase the robustness of your code

218

throw type;

//type: user defined type or principle

type

Throw exception try

{

// code that may generate exceptions

}

catch(type1 id1)

{

// handle exceptions of type1

}

Catch(...)

{

// catch any exception

}

Handling & catching exception

Exception example

219

class DivByZeroEx {};

void div(int num1, int num2)

{

if (num2 == 0) throw (DivByZeroEx ());

}

void main()

{

try

{

div(1, 0);

}

catch (DivByZeroEx ex)

{

printf(" DivByZero Exception ");

}

catch (...)

{

printf("Unkown exception");

}

}

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 220

Endian

big-endian and little-endian refer to which bytes are most significant in multi-byte data types

For example, storing number 1025 in memory (4 bytes)

221

0000.0001 0000.0100 0000.0000 0000.0000

0000.0100 0000.0001 0000.0000 0000.0000

Little endian

Big endian

Endian - Example

Important notes: Avoid to save/load a short/int/long array. Use char (byte) array instead.

222

int main()

{

char num[4] = {0x00,

0x11,

0x22,

0x33};

int *val = (int*)num;

printf("val = 0x%x", *val);

}

val = 0x33221100

Command prompt

Windows 32 bits

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 223

STL

Standard template library Powerful library for container and algorithms Some basic types:

• Vector • Deque • List • ….

Some basic methods • push • pop • insert • copy • erase • …

224

STL

Container

• Vector, deque, set, list, map, hash …

Iterator:

• an object used for selecting the elements within a container and present them to the user

225

STL example

226

#include <cstdio>

#include <list>

using namespace std;

int main()

{

list<int> m_List;

m_List.push_back(10);

m_List.push_back(20);

//travel list

list<int>::iterator i = m_List.begin();

for (i = m_List.begin(); i != m_List.end(); i++)

{

printf("%d\n", *i);

}

return 0;

}

STL and memory management

227

class Element

{

int ID;

public:

Element(int id)

{

printf("Created %d at 0x%x\n", id, this);

ID = id;

}

~Element()

{

printf("Destroy %d at 0x%x\n", ID, this);

}

};

int main()

{

Element e1(0), e2(1);

list<Element> m_List;

//add to list

m_List.push_back(e1); m_List.push_back(e2);

//clear list

printf("-----Before clear-----\n");

m_List.clear();

printf("-----After clear-----\n");

return 0;

}

Created 0 addr 0x22cce8

Created 1 addr 0x22cce4

-----Before clear-----

Destroy 0 addr 0xc91a38

Destroy 1 addr 0xc91a48

-----After clear-----

Destroy 1 addr 0x22cce4

Destroy 0 addr 0x22cce8

Command prompt

???

Copy of Elements are created and stored in list

STL and memory management

228

class Element

{

int ID;

public:

Element(int id)

{

printf("Created %d at 0x%x\n", id, this);

ID = id;

}

~Element()

{

printf("Destroy %d at 0x%x\n", ID, this);

}

};

int main()

{

list<Element*> m_List;

Element *e0 = new Element(0);


//add to list

m_List.push_back(e0); m_List.push_back(e1);

//clear list


m_List.clear();


return 0;

}

Created 0 addr 0xa719c0

Created 1 addr 0xa81a18



Command prompt

Memory leak here

list

Item 0

Item 1

e0

e1

STL and memory management (cont)

229

int main()

{

list<Element*> m_List;



//add to list

m_List.push_back(e0);

m_List.push_back(e1);

//clear list


list <Element*>::iterator i;

for (i = m_List.begin(); i != m_List.end(); i++)

{

delete *i;

}

m_List.clear();


return 0;

}

Free data of each element pointer

Created 0 addr 0xb61a28

Created 1 addr 0xb71a70


Destroy 0 addr 0xb61a28

Destroy 1 addr 0xb71a70


Command prompt

Outline

Preparation

Getting Start

OOP

Memory management


Forward declaration


Template

Type casting

Exception handling

Endian

STL introduction

GNU GCC/G++ 230

GNU GCC

GNU compiler collection include front ends for C, C++, Object-C, …

In windows, using through Cygwin or MinGW

See http://gcc.gnu.org

Read more • makefile • Cygwin • Bash-script • Batch-script

231

http://gcc.gnu.org/

Example

232

@echo off

cls

SET CYGWIN=c:\cygwin\

SET CYGWIN_BIN=%CYGWIN%\bin

SET PATH=%PATH%;%CYGWIN%;%CYGWIN_BIN%

del *.o >nul

if exist main.exe (del main.exe)>nul

%CYGWIN_BIN%\make

if exist main.exe (call main.exe)

make.bat all: main.o MyClass1.o

g++ main.o MyClass1.o -o main.exe

main.o: main.cpp

g++ -c main.cpp

MyClass1.o: MyClass1.cpp

g++ -c MyClass1.cpp

makefile

#include <cstdio>

#include "MyClass1.h"

MyClass::MyClass()

{

printf("Hello\n");

}

MyClass1.cpp #include "MyClass1.h"

int main()

{

MyClass *c = new MyClass();

return 1;

}

main.cpp

#ifndef __MYCLASS_H__

#define __MYCLASS_H__

class MyClass

{

public:

MyClass();

};

#endif

MyClass1.h

Introduction

Design patterns can speed up the development by providing test, proven development paradigm

Allow developers to communicate using well-know, well understood names for software interactions.

See http://sourcemaking.com/designed_patterns for more detail

234

http://sourcemaking.com/designed_patterns


Example Singleton Design Pattern

To Ensure a class has only one instance, and provide a global point of access to it

235

class ExpensiveRes

{

public:

ExpensiveRes() {}

static ExpensiveRes* GetInstance();

private:

static ExpensiveRes* s_Instance;

};

ExpensiveRes* ExpensiveRes::s_Instance = 0;

ExpensiveRes* ExpensiveRes::GetInstance()

{

if (!s_Instance)

{

s_Instance = new ExpensiveRes();

}

return s_Instance;

}

int main()

{

ExpensiveRes::GetInstance();

}

Reference

0 From Java to C – Mihai Popa – Gameloft 0 Thinking in C++, 2nd Edition - Bruce Eckel, President, MindView, Inc. 0 http://en.wikipedia.org 0 http://www.learncpp.com 0 http://msdn.microsoft.com 0 http://www.cplusplus.com 0 http://en.allexperts.com 0 http://www.desy.de/gna/html/cc/Tutorial/tutorial.html 0 http://aszt.inf.elte.hu/~gsd/halado_cpp/ 0 http://www.codeguru.com/forum/showthread.php 0 http://www.uow.edu.au/~nabg/ABC/ABC.html 0 http://pages.cs.wisc.edu/~hasti/cs368/CppTutorial/ 0 http://www.devmaster.net 0 http://enel.ucalgary.ca/People/Normal/enel1315_winter1997/ 0 http://www.cantrip.org 0 http://sourcemaking.com/designed_patterns

236

http://en.wikipedia.org/

http://www.learncpp.com/



http://msdn.microsoft.com/

http://msdn.microsoft.com/

http://www.cplusplus.com/

http://www.cplusplus.com/

http://en.allexperts.com/



http://www.desy.de/gna/html/cc/Tutorial/tutorial.html

http://www.desy.de/gna/html/cc/Tutorial/tutorial.html

http://aszt.inf.elte.hu/~gsd/halado_cpp/

http://aszt.inf.elte.hu/~gsd/halado_cpp/

http://www.codeguru.com/forum/showthread.php

http://www.codeguru.com/forum/showthread.php

http://www.uow.edu.au/~nabg/ABC/ABC.html

http://pages.cs.wisc.edu/~hasti/cs368/CppTutorial/

http://www.devmaster.net/

http://enel.ucalgary.ca/People/Normal/enel1315_winter1997/

http://www.cantrip.org/


Technology

Getting Started Cpp