C错误：类型为'int *'和'unsigned int'的无效操作数为二进制'operator *'|

Question

So, I get this error in C function.

Variables:

int* first_array = (int*) malloc(0);
int first_array_length;

int* second_array = (int*) malloc(0);
int second_array_length;

// Setting up first array
set_up_array(first_array, &first_array_length);

And this is a function:

void set_up_array(int *arr, int *num)
{
    char lenght_msg[] = "Iveskite masyvo ilgi";
    char value_msg[] = "Iveskite masyvo elementa";

    *num = num_scan(0, MAX_SIZE, lenght_msg);
    arr = (int*) realloc(arr, num * sizeof(int)); // <-  error here 
    for (int i = 0; i < (*num); i++)
    {
        arr[i] =  num_scan(INT_MIN, INT_MAX, value_msg);
    }
}

Please, help!

Error:

invalid operands of types 'int*' and 'unsigned int' to binary 'operator*'|

Answer 1

Use *num instead of num in:

realloc(arr, num * sizeof(int));

num is a pointer to int , the value of the int pointee is *num .

And you should not cast the realloc return value.

http://c-faq.com/malloc/mallocnocast.html