int deserialize_students(const Student *dest, const int destCapacityMax)
{
    FILE *ptr_file;
    int i=0;


    ptr_file =fopen("output.txt","r");
    if (!ptr_file)
        return -1;

    if(destCapacityMax==0)
        return -2;

    while (!feof (ptr_file))
    {
        fscanf (ptr_file, "%d", &dest[i].id);    // UB?
        fscanf (ptr_file, "%s",  dest[i].name);
        fscanf (ptr_file, "%d", &dest[i].gender);
        i++;

        if(i==destCapacityMax)
            return 0;

    }
    fclose(ptr_file);
    return 0;
 }

Student students[5];
deserialize_students(students,5);

int func(const int *p) {
  int *q = (int*)p;
  *q = 5;
}

int func(const int *p) {
   fscanf(stdin, "%d", p);
}

warning: writing into constant object (argument 3) [-Wformat=]

int id;
fscanf (ptr_file, "%d", &id);
dest[i].id = id;       // here you get an error