[SOLVED] Checking size of allocated memory

Checking size of allocated memory

I'm writing a program which accepts the size of an array as an argument which should then dynamically allocate memory for that size.

I want my program to return the size of the memory which was allocated. Currently I'm using argv to read the input value and then mmap for the dynamic allocation. I also use a for loop to display what number is saved in each index of the array.

I know allocating could be done with malloc, but I'm not able to use it. I guess I need to start at the last element and check all cells until I get a SEGFAULT signal.

Thanks for your help.

EDIT: Short code without libraries etc...

input = (atoi(argv[1]));
int* arr = mmap(0, input, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, fd, 0);

for (i = 0; i < input; i++) {
    arr[i] = i + 1; 
}

Solution

You can't check the amount of allocated space in C or check the size of arrays. You need to save it as a variable explicitly by yourself.