pointer, malloc and realloc

1

Name entered was 6 char, not enough space to put null terminator

2

Array of char

3

Pointer to array of char

3.cpp(15) : error C2440: '=' : cannot convert from 'int' to 'int *' 4

Pointer to array name[] vs Pointer to variable age (wrong version)

4.cpp(14) : warning C4313: 'printf' : '%d' in format string conflicts with argument 1 of type 'int *' 5

Pointer to array name[] vs Pointer to variable age (correct version)

6

Access address and value pointed by pointer to array name[]Access address and value pointed by pointer to variable age

7

strlen()

8

nameptr points to an empty offset (with size 5 bytes)

allocate new memory using malloc, determine no of offset by strlen

name a z l a n

[0] [1] [2] [3] [4]

nameptr

9

char *strcpy(char *destination, const char *source); The argument order mimics that of an assignment: destination "=" source. The return value is destination

strcpy() – copy value from array to offset

name a z l a n

[0] [1] [2] [3] [4]

nameptr a z l a n

10

Null terminator

nameptr

a z l a n

[0] [1] [2] [3] [4]

\0

[5]

Use for loop to go to each offset

11

a z l a n

[0] [1] [2] [3] [4]nameptr

Go to the next offset

nameptr++a z l a n

[0] [1] [2] [3] [4]

[0] [1] [2] [3]

nameptr++ will makes nameptr point to the next offset

12

a z l a n

[0] [1] [2] [3] [4]name a z l a n

[0] [1] [2] [3] [4]nameptr

12ff5

8

12ff4

c

3631

50

3631

51

3631

52

3631

53

3631

54

12ff5

9

12ff5

a

12ff5

b

12ff5

c

&name = &name[0] = 12ff58

Line 16, create 1 byte x 5 offsetLine 17, copy string from name to nameptr

Check the address for each array name[] element and nameptr offset

13

a z l a n

[0] [1] [2] [3] [4]name

12ff5

8

12ff5

9

12ff5

a

12ff5

b

12ff5

c

&name = &name[0] = 12ff58

a z l a n

[0] [1] [2] [3] [4]tempptr

12ff4

c

3631

50

3631

51

3631

52

3631

53

3631

54

[0]

listptr12

ff40

3631

88

**listptr – pointer to pointer

14

[0]

ptr

12ff6

0

364d

68

[0]

3631

80

[0]

3631

50

[0]36

31b0

[1]

3631

b4

[2]

3631

b8

listptr

12ff5

4

realloc() – continue create a new offset, to point to other address

15

3631

e8

3631

ec

3631

f0

listptr

12ff1

4

a

[0]

ptr

3631

50

l

[1]

3631

51

i

[2]

3631

52

c

[0]

3631

b0

h

[1]

3631

b1

o

[2]

3631

b2

n

[3]

3631

b3

g

[4]

3631

b4

m

[0]

3632

20

u

[1]

3632

21

t

[2]

3632

22

h

[3]

3632

23

u

[4]

3632

24

[0] [1] [2]

when offset=0

when offset=1

when offset=2

Line 11-create new malloc, line 12-copy value from name[] to ptr, line 18-create new offset, line 15 and 19-offset points to where ptr points