How to give condition to my for loop to stop my integer pointer after reading all elements of my int-CodePudding

#include<stdio.h>

#include<stdlib.h>

int main()

{ int a[3];

int *x=(int *) malloc (7*sizeof(int));

int *p=x;

scanf("%d %d %d",&a [0],&a[1],&a [2]); 
for(int i=0;i<3; i  )
{
if(i==0)
for(int j=0; j<3;j  )
    *p  =a[j];
else if (i==1)
    for (int j=0; j<3; j  ) 
    *p  =a[j] a[(j 1)%3];
else
    for(int j=0; j<3;j  )
    *p =a[j];

}
*(  p)= '\0';//id-001

int last=sizeof(x)/sizeof(x[0]); 
printf("%d\n", last); //My expected output is 7 but why I'm getting 2?
p=x;

for(int i=0;p!='\0';i  ){   //id-002
printf("%d ",x[i]);
p  ;
}
}

How should I need to change id-001 to stop my integer pointer?

How should I need to change id-002 my for loop condition to stop after reading stored value in heap array?

CodePudding user response：

int last=sizeof(x)/sizeof(x[0]);

This is incorrect since sizeof() only works for arrays who's size is known at compile time. In your case x is an allocated pointer so this is just dividing the size of a pointer (8 on x86_64) by the size of int (usually 4), hence you get 2.

I'm not sure what you exactly want to do with this program, but the termination condition here can be fixed:

for(int i=0;p!='\0';i ){

Here you're comparing the pointer with a NUL terminatior, not the value that the pointer points to. It should be changed to *p to check the value:

for(int i=0;*p!='\0';i ){

You don't need to advance the pointer again since it would've been advanced by the previous call to *p = something:

*( p) = '\0'; // id-001

So change this to *p = '\0'.

There seems to be a typo in this loop, it should be changed to *p = a[j];:

for (int j = 0; j < 3; j  )
  *p  = a[j];

There is a buffer overflow in the loop itself since p is advanced without any bounds checks. It's advanced a total of 9 times which is out of bounds for size 7.