How to initialize an "empty" sentinel terminated array?

Help
1

Hi. I’m trying to use a sentinel-terminated array as a stack or such. I want to do something like this:

var list: [20:0xffff]u16 = .{}; // sentinel-terminated array with 0xffff in index 0

That does not work, the compiler error is error: expected 20 array elements; found 0, which makes sense.

But then if I do this:

const print = @import("std").debug.print;

pub fn main() !void {
    var list: [20:0xffff]u16 = .{0xffff} ** 20;
    print("Len {}, ", .{list.len});

    list[0] = 1;

    for (list) |x| {
        print("{x} ", .{x});
    }
}

The program prints
Len 20, 1 ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff.
This makes little sense, because Zig documentation states that

The syntax [N:x]T describes an array which has a sentinel element of value x at the index corresponding to the length N.

2

var list: [20:0xffff]u16 = .{0x0000} ** 20; ?

3

I think I have some misconception about these sentinel terminated arrays.
The documentation also states that

    // The sentinel value may appear earlier, but does not influence the compile-time 'len'.
    const array = [_:0]u8 {1, 0, 0, 4};

    try expect(@TypeOf(array) == [4:0]u8);
    try expect(array.len == 4);
    try expect(array[4] == 0);

So it’s not really usable for what I want to do with it anyway.