String to int conversion...

[kavi12_nc]

Hello everybody!

Please have look on this code.

struct record{
int num,password;
char name[10];
};

struct record person[10]; //array of structure
main(){
func1();
}

void func1(){
char *no,*p;
int j,true_id=0;
no=malloc(sizeof(char*));
printf("\nperson.num: %c ",person[1].num);
no=person[1].num; //assignes to array member value
printf("\nno: %c ",no); //statement 1
printf("strtol: %ld",strtol(no,&p,0)); //statment 2 // use of strtol
free(no);
}

As the pointer 'no' can get number in string format, it should return long integer value of that number but i am getting here 0.

The o/p result of statment 1 is '1'.
And the o/p result of statment 2 is 0.?

how will the strtol behave?

[sk_seeker]

This is a buggy program. Here is why:

1.
no = malloc(sizeof(char*)); // 4 bytes of characters

Memory space of 4 bytes (32 bit machine) is being allocated by malloc.
Let us say that the address returned by malloc is 1000.

2.
printf("\nperson.num: %c ",person[1].num);

The array of structures is global initialized data. So, all the structre values are initialized to zero. So, person[1].num will be zero. From the Ascii table, the ASCII code for 0 is 0 (NULL). So, 0 is printed.

3.
no=person[1].num;

This is a bug. Remember that no stores the address returned by malloc?? The above libe just wipes out the address and stores 0 in no i.e. we lost the malloc'ed address i.e. we have created a memory leak!!!

4.
printf("\nno: %c ",no);
This statment will print the Ascii equivalent of zero i.e. zero (NULL).
I do not know how you can get 1 as the answer here. Are you sure you tried this program out??

5.
printf("strtol: %ld",strtol(no,&p,0));
Strtol(Ascii(0)) == Strtol(0) == 0

6.
free(no);
This is another bug as there is nothing to free as the malloc'ed address i.e. 1000, has already been overwritten to 0.

Hope that helps.

[kavi12_nc]

thank you. I found more bugs in addition with pointed out by u.

I'll come back soon with proper code n' query.

[kavi12_nc]

struct record{
int num,password;
char name[10];
};

struct record person[2]={1,6,"ka", 2, 5, "123"};; //array of structure

void func1();

void main(){
clrscr();
func1();
getch();
}

void func1(){
char *no,*p;
int j,true_id=0;
//no=malloc(sizeof(char*));
printf("\nperson.num: %d ",person[1].num);
printf("\nperson.password: %d ",person[1].password);
printf("\nperson.name: %s ",person[1].name);
no=&person[1].name; //assignes to array member value
printf("\nno: %s",no); //statement 1
printf("\nstrtol: %ld",strtol(no,&p,0)); //statment 2 // use of strtol
//free(no);
}


here is the repaired code. Though my string"123" get changed to "kavita", the strtol returns the same no.(I was expecting to change the long int value as my string changed)???