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Dereferencing double pointer to pass to recursive function


By : jamie p
Date : October 18 2020, 06:10 PM
Hope that helps To answer the question as asked:
void tree_input() takes a pointer to a pointer as an argument, and node_s->left is a pointer. So all you have to do is get a pointer to the pointer by using the address-of operand.
code :
tree_input(value, &(*tmproot)->left);


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Dereferencing a double pointer just once?


By : fohinni
Date : March 29 2020, 07:55 AM
To fix the issue you can do Trace the execution with gdb, then you will see that the last line *iPtr2=iPtr1 doesn't change anything. (it's kind of like iPtr1=iPtr1)
On iPtr2 = &iPtr1;, the iPtr2 already points to the address where iPtr1 THE POINTER lies NOT THE ADDRESS iPtr1 points to.

Dereferencing a double-level pointer results in different behaviour from dereferencing a single-level pointer


By : Wissem BL Maraghni
Date : March 29 2020, 07:55 AM
like below fixes the issue They are very different things. An int** is a pointer to a pointer to an int. If you dereference it, you get an int*. An int* is a pointer to an int. If you dereference it, you get an int.
In the first example, you pass an int** with value 0x4df73c as the first argument to work. You then dereference this, which should give you an int*. That is, 0x4df73c is the address of an address and doing *pointer has gotten you the second addess. You then do pointer arithmetic with this int* by adding (offset/sizeof(int)), which works out how many ints there are with offset bytes. So when you add this value, your int* will move along to point at the int at that offset. You then return this int* and all is well.
code :
return (int*) (*pointer + offset);

dereferencing pointer that was cast to double pointer


By : Cat Z
Date : March 29 2020, 07:55 AM
it helps some times I am having some trouble understanding these two lines of code.
code :
Free = *((T**)Free);
Free = (T *) *Free;

Dereferencing double pointer


By : Ville Leinonen
Date : March 29 2020, 07:55 AM
With these it helps This program should produce multiple compiler warnings. Fixing them goes long way toward fixing the problem, and clearing out any misunderstandings.
The type of b is an array of pointer-to-pointer-to-int. That's why the two assignment below are invalid:
code :
*(b+0)= &val1; 
*(b+1) = &val2; 
printf("%d\n", b[0][0]); 
int **b[3];
...
*(b+2) = &val3;
int *b[3];
...
*(b+2) = val3;

Dereferencing pointer to a pointer doesn't work when I pass it to a function. Why? (C)


By : netslayer
Date : September 27 2020, 02:00 AM
like below fixes the issue The error is that this 2D-array is laid out as 4 x 4 = 16 integers. But your function expects a pointer to pointers.
It's right that at the calling site the address of matrix is provided as the argument. But unlike some commenter said, it's not a pointer to int but a pointer to an int-array.
code :
void test_matrix(int (*matrix)[4])
{
    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            printf("%d ", *(*(matrix + i) + j));
        }
    }
}
void test_matrix(int matrix[][4])
{
    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            printf("%d ", matrix[i][j]);
        }
    }
}
*(*(matrix + i) + j)

matrix[i][j]
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