realloc question

I've been playing with pointers and dynamic memory allocation for the last couple of days. Did I get the code below right? I want ptr1 and ptr2 to point to the same memory location. I suppose the address of the memory "block" might change after the call to realloc, so I put the address in ptr1 to ptr2 again. Is that correct?

Code:

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int *ptr1, *ptr2;

ptr1 = (int *)malloc(sizeof(int));
ptr2 = ptr1;

/* some code here*/

ptr1 = realloc(ptr1, 3);

ptr2 = ptr1; // Necessary?

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Yes it's necessary after realloc()... as you correctly discerned, the address can/will change.

Also beware of your malloc() calls... sizeof(int) will allocate only 4 bytes (the size of an integer variable) or as few as 2 bytes if you are in India.

Yes it is necessary.