addAddr

        pub fn addAddr(t: *@This(), addr: usize, note: []const u8) void {
            if (!enabled) return;

            if (t.index < size) {
                t.notes[t.index] = note;
                const addrs = &t.addrs[t.index];
                const st = captureCurrentStackTrace(.{ .first_address = addr }, addrs);
                if (st.return_addresses.len < addrs.len) {
                    @memset(addrs[st.return_addresses.len..], 0); // zero unused frames to indicate end of trace
                }
            }
            // Keep counting even if the end is reached so that the
            // user can find out how much more size they need.
            t.index += 1;
        }