Check if pointer is not initialized (very easy)

//well, I do not know if this is correct, I was trying to check if a pointer had not been started
//when I remembered to do that! and it worked

#include <stdio.h>

int main(void) {
    int* allval;
    if(allval == (int*)0) {
        printf("sim\n");
    }
    else {
        printf("nao\n");
    }

    allval = (int*)malloc(5 * sizeof(int));
    if(allval == (int*)0) {
        printf("sim\n");
    }
    else {
        printf("nao\n");
    }
    return 0;
}