I don't see how the code assumes anything about the placement of the array. Indeed, it works just fine for static arrays: $ cat test.c #include <stdio

I don't see how the code assumes anything about the placement of the array. Indeed, it works just fine for static arrays: $ cat test.c #include <stdio.h> int arr[5]; int main(int argc, char *argv[]) { printf("%lu, %ld\n", sizeof(arr) / sizeof(*arr), (&arr)[1] - arr); } $ gcc test.c && ./a.out 5, 5 Not saying it's "a good way to program" - it's needlessly obfuscated compared to the standard sizeof alternative. But it doesn't rely on anything tricky.