How to type cast an void pointer to array pointer in c?

Question

**The dynamically allocated functions malloc,calloc,realloc in the stdlib library returns the void pointer

I want to convert the void pointer retuned to an array pointer is it possible to do so **

void* x=malloc(6*sizeof(int));
int (*ptr)[3];

Can we typecast x and assign it to ptr?

Answer 1

You can implicitly convert x to ptr via the assignment:

int (*ptr)[3] = x;

or use an explicit cast:

int (*ptr)[3] = (int (*)[3]) x;

As x is a pointer to array of 6 ints, I am not sure why you want a pointer to the first 3 of these. gcc -Wall -Wextra... doesn't even generate a warning for out of bound access printf("%d\n", (*ptr)[4]); so why use aa plain int *ptr ?

int *ptr = malloc(6 * sizeof(int));

Answer 2

The 'normal' way to do this is

int *ptr = malloc(6*sizeof(int));

or maybe

int *ptr = malloc(3*sizeof(int));

since you dont seem to know if you want 3 or 6 ints

Answer 3

1D array of 6 int :

int* arr = malloc(6 * sizeof *arr);
...
arr[i] = something;
...
free(arr);

2D array of 2x3 int :

int (*arr)[3] = malloc( sizeof(int[2][3]) );
...
arr[i][j] = something;
...
free(arr);

In either case there is no need of a void* as a middle step.