c - Is `*((*(&array + 1)) - 1)` safe to use to get the last element of an automatic array?

Question

Suppose I want to get the last element of an automatic array whose size is unknown. I know that I can make use of the sizeof operator to get the size of the array and get the last element accordingly.

Is using *((*(&array + 1)) - 1) safe?

Like:

char array[SOME_SIZE] = { ... };
printf("Last element = %c", *((*(&array + 1)) - 1));

int array[SOME_SIZE] = { ... };
printf("Last element = %d", *((*(&array + 1)) - 1));

etc

Answer 1

No, it is not.

&array is of type pointer to char[SOME_SIZE] (in the first example given). This means &array + 1 points to memory immediately past the end of array. Dereferencing that (as in (*(&array+1)) gives undefined behaviour.

No need to analyse further. Once there is any part of an expression that gives undefined behaviour, the whole expression does.