Unable to get proper output, using void pointer to store and read dynamically allocated array.

NevemTeve · 06-22-2023, 02:38 PM

Your program is not unsalvable; please make an effort to understand the changes.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right);

static int cmp(const void *pa, const void *pb)
{
    int a= *(int *)pa;
    int b= *(int *)pb;
    if (a<b)       return -1;
    else if (a==b) return  0;
    else           return  1;
}

int main(){
    int *intvals = NULL; //array of integers
    int **vals= NULL;//array of pointers
    int total_elements;

    if (isatty(fileno(stdin))) {
        printf("How many elements in the array");
    }
    scanf("%d", &total_elements);

    intvals = malloc(total_elements*sizeof(int));
    vals = malloc(total_elements*sizeof(int *));
    for(int i= 0; i<total_elements; ++i) {
        vals[i]= &intvals[i];
        scanf("%d", vals[i]);
    }
    printf("unsorted:");
    for (int i=0; i<total_elements; ++i) {
        printf(" %d", *vals[i]);
    }
    fputc('\n', stdout);

    do_qsort((void **)vals, cmp, 0, total_elements-1);

    printf("sorted:");
    for (int i=0; i<total_elements; ++i) {
        printf(" %d", *vals[i]);
    }
    fputc('\n', stdout);

    free(vals);
    free(intvals);
    return 0;
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex);

static void swap(void **arr, int i, int j) {
    void *tmp= arr[i];
    arr[i]= arr[j];
    arr[j]= tmp;
}

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right){
    int pivotIndex;

    if (right<= left) return;
    else if (left+1==right) {
        if (cmp(ar[left], ar[right])>0) {
            swap(ar, left, right);
        }
        return;
    }

    pivotIndex = (left+right+1)/2;
    pivotIndex = partition(ar, cmp, left, right, pivotIndex);
    do_qsort(ar, cmp, left, pivotIndex-1);
    do_qsort(ar, cmp, pivotIndex+1, right);
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex){
       int idx, store; void *pivot = ar[pivotIndex]; void *tmp = ar[right];
       ar[right] = ar[pivotIndex];  ar[pivotIndex]= tmp;
       store = left;
       for(idx= left; idx<right;idx++){
           if(cmp(ar[idx], pivot) <=0){
                  tmp = ar[idx]; ar[idx]=ar[store]; ar[store]=tmp; store++;
           }
       }
       tmp= ar[right];  ar[right] = ar[store];  ar[store] = tmp;

       return store;
}

digitechroshni · 06-28-2023, 05:03 AM

There is an error in the code you provided. The error is in the line where you use the "scanf" function inside the first for loop:
scanf("%d", ((int *)arr)[i]);

The issue is with the argument you're passing to scanf. The scanf function expects the address of the variable where it should store the input value, using the & operator. However, in your code, you're not providing the address correctly.

To fix the error, you need to pass the address of the array element to scanf. You can do this by using the & operator before ((int *)arr)[i]. The corrected line should be:
scanf("%d", &((int *)arr)[i]);

I hope this work!
Happy coding!

ajiten · 07-02-2023, 07:18 AM

Quote:

Originally Posted by digitechroshni

There is an error in the code you provided. The error is in the line where you use the "scanf" function inside the first for loop:
scanf("%d", ((int *)arr)[i]);

The issue is with the argument you're passing to scanf. The scanf function expects the address of the variable where it should store the input value, using the & operator. However, in your code, you're not providing the address correctly.

To fix the error, you need to pass the address of the array element to scanf. You can do this by using the & operator before ((int *)arr)[i]. The corrected line should be:
scanf("%d", &((int *)arr)[i]);

I hope this work!
Happy coding!

Thanks. Request to tell error in my earlier code, that fails by giving: 'Segmentation Fault', after accepting input numbers. It is also stated below.
My main concern is that, am unable to find the reason for segmentation fault; inspite of trying hard to figure the same.

Code:

#include <stdio.h>
#include<stdlib.h>
//int partition(void **, int, int *, int, int , int);
int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex);
int cmp(const void *, const void*);
//void do_qsort(void **, int *(const void *, const void*), int, int);
void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right);
int selectPivotIndex(int, int);

int main(){
	void ** vals;//array of pointers
        int total_elements, *intvals;
	printf("How many elements--in the array: : ");
	scanf("%d", &total_elements);
	vals = malloc(total_elements*sizeof(int));

        intvals = malloc(total_elements*sizeof(int));
        for(int i=0; i<total_elements; i++) scanf("%d", &intvals[i]);
        vals = malloc(total_elements*sizeof(int *));
 
        for(int i=0; i<total_elements; i++) *(int *)vals[i]= &intvals[i];   //*vals[i] = &intvals[i];
        do_qsort(vals, cmp, 0, total_elements-1);
        for(int i=0; i<total_elements; i++) printf("%d\n", *(int *)vals[i]);

	/*for(int i=0; i<total_elements; i++) scanf("%d", (int *)vals+i);
        //for(int **p=(int **)vals, **end = p+total_elements; **p<total_elements; p++)
	for(int **p=(int **)vals; **p<total_elements; p++)
		scanf("%d", *p);
	do_qsort(vals, cmp, 0, total_elements-1);
        printf("correct");
        for(int i =0; i<total_elements; i++)
        	printf("Element #%d, is: %d", i, vals[i]);
        return 1;*/
}

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right){
	int pivotIndex;
        printf("q_sort");
        printf("entered do_qsort\n with left element index: %d, left element:%d, right element index: %d", left, (int *)(*ar+left), (int *)(*ar +right));// (int *)(*ar)[left], (int *)(*ar)[right]);
	if (right<= left) return;
        pivotIndex = selectPivotIndex(left, right);
	pivotIndex = partition(ar, cmp, left, right, pivotIndex);
	do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotIndex+1, right);
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex){
       int idx, store; void *pivot = ar[pivotIndex]; void *tmp = ar[right]; 
       ar[right] = ar[pivotIndex];  ar[pivotIndex]= tmp;
       store = left;
       for(idx= left; idx<right;idx++){
	       if(cmp(ar[idx], pivot) <=0){
	              tmp = ar[idx]; ar[idx]=ar[store]; ar[store]=tmp; store++;
	       }
       }
       tmp= ar[right];  ar[right] = ar[store];  ar[store] = tmp;

       return store;
}

int cmp(const void * a, const void *b)
{
      if ((int*)a<=(int*)b)  return 0;
      else return 1;
}

int selectPivotIndex(int left, int right)
{
      int median;
      median = (left+right)/2;
      if(median %2==0) median = median +1;
      return median;
}

Segmentation fault:

Code:

$ ./quicksort
How many elements--in the array: : 5
10
5
23
8
29
Segmentation fault (core dumped)

pan64 · 07-03-2023, 12:26 AM

you might want to try valgrind. It can easily identify it.
(it is not that difficult, just a few lines of additional code: https://valgrind.org/docs/manual/qui...ck-start.mcrun)

NevemTeve · 07-03-2023, 01:28 AM

You forgot compiler-option -W -Wall -Werror -pedantic
Now try to debug this version:

Code:

#include <stdio.h>
#include<stdlib.h>
//int partition(void **, int, int *, int, int , int);
int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex);
int cmp(const void *, const void*);
//void do_qsort(void **, int *(const void *, const void*), int, int);
void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right);
int selectPivotIndex(int, int);

int main(){
    void ** vals;//array of pointers
        int total_elements, *intvals;
    printf("How many elements--in the array: : ");
    scanf("%d", &total_elements);
    vals = malloc(total_elements*sizeof(int*));

        intvals = malloc(total_elements*sizeof(int));
        for(int i=0; i<total_elements; i++) scanf("%d", &intvals[i]);
        vals = malloc(total_elements*sizeof(int *));

        for(int i=0; i<total_elements; i++) vals[i]= &intvals[i];   //*vals[i] = &intvals[i];
        do_qsort(vals, cmp, 0, total_elements-1);
        for(int i=0; i<total_elements; i++) printf("%d\n", *(int *)vals[i]);

    /*for(int i=0; i<total_elements; i++) scanf("%d", (int *)vals+i);
        //for(int **p=(int **)vals, **end = p+total_elements; **p<total_elements; p++)
    for(int **p=(int **)vals; **p<total_elements; p++)
        scanf("%d", *p);
    do_qsort(vals, cmp, 0, total_elements-1);
        printf("correct");
        for(int i =0; i<total_elements; i++)
        printf("Element #%d, is: %d", i, vals[i]);
        return 1;*/
}

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right){
    int pivotIndex;
        printf("q_sort");
        printf("entered do_qsort\n with left element index: %d, left element:%d, right element index: %d",
             left, *(int *)ar[left], *(int *)ar[right]);
    if (right<= left) return;
        pivotIndex = selectPivotIndex(left, right);
    pivotIndex = partition(ar, cmp, left, right, pivotIndex);
    do_qsort(ar, cmp, left, pivotIndex-1);
    do_qsort(ar, cmp, pivotIndex+1, right);
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex){
       int idx, store; void *pivot = ar[pivotIndex]; void *tmp = ar[right];
       ar[right] = ar[pivotIndex];  ar[pivotIndex]= tmp;
       store = left;
       for(idx= left; idx<right;idx++){
           if(cmp(ar[idx], pivot) <=0){
                  tmp = ar[idx]; ar[idx]=ar[store]; ar[store]=tmp; store++;
           }
       }
       tmp= ar[right];  ar[right] = ar[store];  ar[store] = tmp;

       return store;
}

int cmp(const void * a, const void *b)
{
      if ((int*)a<=(int*)b)  return 0;
      else return 1;
}

int selectPivotIndex(int left, int right)
{
      int median;
      median = (left+right)/2;
      if(median %2==0) median = median +1;
      return median;
}

bigearsbilly · 07-19-2023, 04:15 AM

Quote:

request vetting of the reason why "scanf("%d", ((int *)arr+i));" works, when "scanf("%d", ((int *)arr)[i]);" fails.

As mentioned by others:
the square brackets array\[\] automatically dereferences the array's contents, whereas array + i does not.
So the with the [] you get back an int

Code:

#include <stdio.h>

int main(void)
{
        int array[] = { 0,1,2,3,4,5};
        printf("%d\n", array[3]);
        printf("%d\n", *(array +3));

return 0;
}

ajiten · 07-22-2023, 05:49 AM

Quote:

Originally Posted by NevemTeve

Your program is not unsalvable; please make an effort to understand the changes.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right);

static int cmp(const void *pa, const void *pb)
{
    int a= *(int *)pa;
    int b= *(int *)pb;
    if (a<b)       return -1;
    else if (a==b) return  0;
    else           return  1;
}

int main(){
    int *intvals = NULL; //array of integers
    int **vals= NULL;//array of pointers
    int total_elements;

    if (isatty(fileno(stdin))) {
        printf("How many elements in the array");
    }
    scanf("%d", &total_elements);

    intvals = malloc(total_elements*sizeof(int));
    vals = malloc(total_elements*sizeof(int *));
    for(int i= 0; i<total_elements; ++i) {
        vals[i]= &intvals[i];
        scanf("%d", vals[i]);
    }
    printf("unsorted:");
    for (int i=0; i<total_elements; ++i) {
        printf(" %d", *vals[i]);
    }
    fputc('\n', stdout);

    do_qsort((void **)vals, cmp, 0, total_elements-1);

    printf("sorted:");
    for (int i=0; i<total_elements; ++i) {
        printf(" %d", *vals[i]);
    }
    fputc('\n', stdout);

    free(vals);
    free(intvals);
    return 0;
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex);

static void swap(void **arr, int i, int j) {
    void *tmp= arr[i];
    arr[i]= arr[j];
    arr[j]= tmp;
}

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right){
    int pivotIndex;

    if (right<= left) return;
    else if (left+1==right) {
        if (cmp(ar[left], ar[right])>0) {
            swap(ar, left, right);
        }
        return;
    }

    pivotIndex = (left+right+1)/2;
    pivotIndex = partition(ar, cmp, left, right, pivotIndex);
    do_qsort(ar, cmp, left, pivotIndex-1);
    do_qsort(ar, cmp, pivotIndex+1, right);
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex){
       int idx, store; void *pivot = ar[pivotIndex]; void *tmp = ar[right];
       ar[right] = ar[pivotIndex];  ar[pivotIndex]= tmp;
       store = left;
       for(idx= left; idx<right;idx++){
           if(cmp(ar[idx], pivot) <=0){
                  tmp = ar[idx]; ar[idx]=ar[store]; ar[store]=tmp; store++;
           }
       }
       tmp= ar[right];  ar[right] = ar[store];  ar[store] = tmp;

       return store;
}

Compiled on onlinegdb.com.

On sample data of 10 values, in input; as: 15, 1, 30, 2, 70, 3, 65, 3, 4, 91
wanted to see the actual execution, by modifying the code as shown below:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right, int counter);

static int cmp(const void *pa, const void *pb)
{
    int a= *(int *)pa;
    int b= *(int *)pb;
    if (a<b)       return -1;
    else if (a==b) return  0;
    else           return  1;
}

int main(){
    int *intvals = NULL; //array of integers
    int **vals= NULL;//array of pointers
    int total_elements;

    if (isatty(fileno(stdin))) {
        printf("How many elements in the array: ");
    }
    scanf("%d", &total_elements);

    intvals = malloc(total_elements*sizeof(int));
    vals = malloc(total_elements*sizeof(int *));
    for(int i= 0; i<total_elements; ++i) {
        vals[i]= &intvals[i];
        scanf("%d", vals[i]);
    }
    printf("unsorted:");
    for (int i=0; i<total_elements; ++i) {
        printf(" %d", *vals[i]);
    }
    fputc('\n', stdout);

    do_qsort((void **)vals, cmp, 0, total_elements-1, 0);

    printf("sorted:");
    for (int i=0; i<total_elements; ++i) {
        printf(" %d", *vals[i]);
    }
    fputc('\n', stdout);

    free(vals);
    free(intvals);
    return 0;
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex);

static void swap(void **arr, int i, int j) {
    void *tmp= arr[i];
    arr[i]= arr[j];
    arr[j]= tmp;
}

void do_qsort(void **ar, int(*cmp)(const void *, const void *), int left, int right, int counter){
    int pivotIndex;
    printf ("\n ============ do_qsort() counter : %d, left: %d,  right: %d\n", counter, left, right);
    if (right<= left) return;
    else if (left+1==right) {
        if (cmp(ar[left], ar[right])>0) {
            swap(ar, left, right);
        }
        return;
    }
    
    pivotIndex = (left+right+1)/2;
    pivotIndex = partition(ar, cmp, left, right, pivotIndex);
    printf("\n counter: %d", counter);
    do_qsort(ar, cmp, left, pivotIndex-1, counter+1);
    do_qsort(ar, cmp, pivotIndex+1, right, counter+1);
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int pivotIndex){
       int idx, store; 
       int current_elements = right - left +1;
       void *pivot = ar[pivotIndex]; void *tmp = ar[right];
       ar[right] = ar[pivotIndex];  ar[pivotIndex]= tmp;
       store = left;
       printf("partition: current: left: %d, right: %d, current_elements: %d::", left, right, current_elements);
       for (int i=0; i<current_elements; ++i)
                    printf(" %d", (int *)ar[i]); //Unable to get any meaningful output of it, as shown below 
       for(idx= left; idx<right;idx++){
           if(cmp(ar[idx], pivot) <=0){ printf("\n idx: %d, store: %d, left: %d, right: %d", idx, store, left, right);
                  tmp = ar[idx]; ar[idx]=ar[store]; ar[store]=tmp; store++;
           }
       }
       tmp= ar[right];  ar[right] = ar[store];  ar[store] = tmp;

       return store;
}

Q.1. Have confusion as what is the output implied by the line #84, 85; i.e.

Code:

for (int i=0; i<current_elements; ++i)
                    printf(" %d", (int *)ar[i]);

as that gives output as shown below. Say, on the first iteration, it gives the output as: -1508742464 -1508742460 -1508742456 -1508742452 -1508742448 -1508742428 -1508742440 -1508742436 -1508742432 -1508742444;
which though are the set of 10 values in the array for each of the 10 iterations, but cannot link to the actual elements in the array.

Code:

main.c: In function ‘partition’:
main.c:85:31: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int *’ [-Wformat=]
   85 |                     printf(" %d", (int *)ar[i]);
      |                              ~^   ~~~~~~~~~~~~
      |                               |   |
      |                               int int *
      |                              %ls

How many elements in the array: 10
15
1
30
2
70
91
65
3
4
3
unsorted: 15 1 30 2 70 91 65 3 4 3

 ============ do_qsort() counter : 0, left: 0,  right: 9
partition: current: left: 0, right: 9, current_elements: 10:: -1508742464 -1508742460 -1508742456 -1508742452 -1508742448 -1508742428 -1508742440 -1508742436 -1508742432 -1508742444
 idx: 0, store: 0, left: 0, right: 9
 idx: 1, store: 1, left: 0, right: 9
 idx: 2, store: 2, left: 0, right: 9
 idx: 3, store: 3, left: 0, right: 9
 idx: 4, store: 4, left: 0, right: 9
 idx: 5, store: 5, left: 0, right: 9
 idx: 6, store: 6, left: 0, right: 9
 idx: 7, store: 7, left: 0, right: 9
 idx: 8, store: 8, left: 0, right: 9
 counter: 0
 ============ do_qsort() counter : 1, left: 0,  right: 8
partition: current: left: 0, right: 8, current_elements: 9:: -1508742464 -1508742460 -1508742456 -1508742452 -1508742432 -1508742428 -1508742440 -1508742436 -1508742448
 idx: 0, store: 0, left: 0, right: 8
 idx: 1, store: 1, left: 0, right: 8
 idx: 2, store: 2, left: 0, right: 8
 idx: 3, store: 3, left: 0, right: 8
 idx: 4, store: 4, left: 0, right: 8
 idx: 5, store: 5, left: 0, right: 8
 idx: 6, store: 6, left: 0, right: 8
 idx: 7, store: 7, left: 0, right: 8
 counter: 1
 ============ do_qsort() counter : 2, left: 0,  right: 7
partition: current: left: 0, right: 7, current_elements: 8:: -1508742464 -1508742460 -1508742456 -1508742452 -1508742436 -1508742428 -1508742440 -1508742432
 idx: 1, store: 0, left: 0, right: 7
 idx: 3, store: 1, left: 0, right: 7
 idx: 4, store: 2, left: 0, right: 7
 idx: 5, store: 3, left: 0, right: 7
 counter: 2
 ============ do_qsort() counter : 3, left: 0,  right: 3
partition: current: left: 0, right: 3, current_elements: 4:: -1508742460 -1508742452 -1508742428 -1508742436
 idx: 0, store: 0, left: 0, right: 3
 idx: 1, store: 1, left: 0, right: 3
 idx: 2, store: 2, left: 0, right: 3
 counter: 3
 ============ do_qsort() counter : 4, left: 0,  right: 2
partition: current: left: 0, right: 2, current_elements: 3:: -1508742460 -1508742428 -1508742452
 idx: 0, store: 0, left: 0, right: 2
 counter: 4
 ============ do_qsort() counter : 5, left: 0,  right: 0

 ============ do_qsort() counter : 5, left: 2,  right: 2

 ============ do_qsort() counter : 4, left: 4,  right: 3

 ============ do_qsort() counter : 3, left: 5,  right: 7
partition: current: left: 5, right: 7, current_elements: 3:: -1508742460 -1508742452 -1508742428
 idx: 5, store: 5, left: 5, right: 7
 idx: 6, store: 6, left: 5, right: 7
 counter: 3
 ============ do_qsort() counter : 4, left: 5,  right: 6

 ============ do_qsort() counter : 4, left: 8,  right: 7

 ============ do_qsort() counter : 2, left: 9,  right: 8

 ============ do_qsort() counter : 1, left: 10,  right: 9
sorted: 1 2 3 3 4 15 30 65 70 91

Q.2. How to remove the warning obtained on compilation, in onlinegdb.com?

NevemTeve · 07-22-2023, 06:24 AM

Code:

- printf(" %d", (int *)ar[i]);
+ printf(" %d", *(int *)ar[i]);

dugan · 07-22-2023, 11:03 AM

You can go to https://cdecl.org/ to check some of these.

The advice here should also help:

https://c-faq.com/decl/cdecl1.html

ajiten · 07-22-2023, 11:05 AM

Quote:

Originally Posted by NevemTeve

Code:

- printf(" %d", (int *)ar[i]);
+ printf(" %d", *(int *)ar[i]);

The reason it worked, must be that need to both type-cast the contents of array (being a pointer to a pointer to an integer), and the fact that ar[i] = *(ar+i); hence *ar[i] = **(ar +i).
But, that means that (int *)*ar[i] should work too.
But, that gives error:

Code:

main.c: In function ‘partition’:
main.c:85:42: warning: dereferencing ‘void *’ pointer
   85 |                     printf(" %d", (int *)*ar[i]);
      |                                          ^~~~~~
main.c:85:35: error: invalid use of void expression
   85 |                     printf(" %d", (int *)*ar[i]);
      |                                   ^

Please tell why?

astrogeek · 07-22-2023, 12:52 PM

Quote:

Originally Posted by ajiten

The reason it worked, must be that need to both type-cast the contents of array (being a pointer to a pointer to an integer), and the fact that ar[i] = *(ar+i); hence *ar[i] = **(ar +i).
But, that means that (int *)*ar[i] should work too...

You state that as if it were fact, but clearly it is not.

The error message is very precise, trust it.

This works because the pointer to void pointer is typecast before being dereferenced...

Code:

printf(" %d", *(int *)ar[i]);

This produces the error because the pointer to void pointer is first being dereferenced, then its value is being typecast...

Code:

printf(" %d", (int *)*ar[i]);

And the error tells you exactly that, and exactly where...

Code:

main.c:85:42: warning: dereferencing ‘void *’ pointer
   85 |                     printf(" %d", (int *)*ar[i]);
      |                                          ^~~~~~

The two expressions are not equivalent.

pan64 · 07-22-2023, 01:49 PM

the * itself is not a typecast but an operator. (int *) is a typecast.

ajiten · 07-22-2023, 02:51 PM

Quote:

Originally Posted by astrogeek

You state that as if it were fact, but clearly it is not.

The error message is very precise, trust it.

This works because the pointer to void pointer is typecast before being dereferenced...

Code:

printf(" %d", *(int *)ar[i]);

This produces the error because the pointer to void pointer is first being dereferenced, then its value is being typecast...

Code:

printf(" %d", (int *)*ar[i]);

And the error tells you exactly that, and exactly where...

Code:

main.c:85:42: warning: dereferencing ‘void *’ pointer
   85 |                     printf(" %d", (int *)*ar[i]);
      |                                          ^~~~~~

The two expressions are not equivalent.

Have confusion as what is the output given by the earlier code; i.e.

Code:

for (int i=0; i<current_elements; ++i)
                    printf(" %d", (int *)ar[i]);

i.e., on sample data of 10 values, in input as: 15, 1, 30, 2, 70, 3, 65, 3, 4, 91;
gives output on the first iteration as: -1508742464 -1508742460 -1508742456 -1508742452 -1508742448 -1508742428 -1508742440 -1508742436 -1508742432 -1508742444

NevemTeve · 07-22-2023, 03:55 PM

That happens, when you print a pointer (int *) as an int (%d).

pan64 · 07-22-2023, 04:21 PM

you ought to use printf "%p" for pointers, instead of %d (but you can try %x too, if you wish).
The pointer itself is the location (address) of the variable in the memory, therefore it is actually an integer (or long).
see for example here: https://www.man7.org/linux/man-pages/man3/printf.3.html