[guerby]

On https://godbolt.org/ select Ada and compiler option "-O2"

    function Square(num : Integer) return Integer is
        tab : array (0..100) of integer;
    begin
        for i in 0..101 loop 
            tab(i):=i; 
        end loop;
        return tab(100);
    end Square;

The assembly code generated is :

    sub     rsp, 8    #,
    mov     esi, 11   #,
    mov     edi, OFFSET FLAT:.LC0     #,
    call    "__gnat_rcheck_CE_Index_Check"  #

Loop is not run and exeption handler is called directly.

Link : https://godbolt.org/z/qT4TsKPxz

[Animats]

Right, that's the extreme case, where the problem is detected at compile time. Unfortunately, it's not a user-visible error message at compile time.

Need to try an example where the size isn't known until run time.