How exactly find out length of ADT vector in C which is type of uint64_t?

I am trying to find out how to find the length of an ADT array type of uint64_t in C.

The code I wrote:

char * uint64_t(char * uint64_t, const char *restrict sep);

int size = sizeof(uint64_t) / sizeof(uint64_t[0]);

printf("Size of  vektor:", %zu, sizeof(uint64_t[0]));

I am not able to change any variables because it is prohibited by its creator (my professor) of whole code I can only implement some functions.

>Solution :

You cannot find the size of an array passed as a pointer into a function.

The compiler has no way of knowing how big it is, either

• pass in the length as an arg
• have a sentinel value, 0, -1, MAX_INT etc

I have ignored the fact that your code very messsed up , I assume you are trying to do this

 void func(uint64_t *arr , const char *restrict sep){
    int size = sizeof(arr) / sizeof(arr[0]);
    printf("Size of  vektor: %d", size);
}