C++ :: Vulnerable Recursive Programming On Define

I've been studying "algorithm" by myself by book. And there's this part - vulnerable point of "define" syntax on recursive programming.

Code:

int max_arr2(int arr[], int arr_len) {
int (arr_len == 1)
return arr[0];
else
return max(arr[arr_len-1], max_arr2(arr, arr_len-1);
.
.

This book says, " function 'max_arr2' is just recursive function, without any problem. but if max() is defined like this,

#define max(x,y) ((x)>(y) ? (x):(y))

and if array is just declined, it will take very long time."

I typed this code and run, and actually it really takes long time.