Content of array pointer is altered outside the loop

Question

I'm initializing the values of an array pointer inside a function by allocating it first, and then allocating its content (struct pointers) iterating over the reading of values.

Those are the definition of Richiesta and the content of the initializing function:

    typedef struct richiesta {
        int durata;
    } *Richiesta;

    void leggiParametri(Richiesta **richieste, int *n){
        // size
        scanf("%d", n);

        *richieste = calloc(*n, sizeof(struct richiesta));

        //printf("Inside loop:\n");
        for(int i = 0; i < *n; i++){
            Richiesta richiesta = malloc(sizeof(struct richiesta));
            printf("%d\t", richiesta);
            scanf("%d", &richiesta->durata);
            (*richieste)[i] = richiesta;
            printf("%d: %d\n", i, (*richieste)[i]->durata);
        }
        printf("Outside loop:\n");
        printf("%d: %d\n", 0, (*richieste)[0]->durata);
        printf("%d: %d\n", 1, (*richieste)[1]->durata);
    }

The main body:

    Richiesta *richieste = NULL;
    int n = -1;
    leggiParametri(&richieste, &n);

Giving the following input:

6
4
7
3
8
1
5
15

the output is:

-858131760  0: 4
-858127616  1: 7
-858127584  2: 3
-858127552  3: 8
-858127520  4: 1
-858127488  5: 5
Outside loop:
0: -858127520
1: 7

The problem occurs only for the first element of the array, in the for loop it contains the correct value read, while outside it contains that particular value, which corresponds to the address pointed to by the 5th element (printed as an integer). (the same thing happens even printing the array content inside either an other function or main body)

• What causes the problem?
• Why does it point to that specific value?
• And is there any way to make it work?

Also, uncommenting the line of printf("Inside loop:\n"); returns a segmentation fault when printing.

Answer 1

You did not allocate an array of pointers in this statement

*richieste = calloc(*n, sizeof(struct richiesta));

where the type specifier Richiesta as you wrote in a comment is an alias for the type struct richiesta. You allocated an array of structures.

So this assignment

(*richieste)[i] = richiesta;

does not make a sense.

It seems you mean

*richieste = calloc(*n, sizeof( Richiesta ));

Pay attention to that using a typedef for a pointer like this

typedef struct richiesta *Richiesta;

is a bad idea. This only confuses readers of the code.