Question: Why kilo allocating 9 bytes memory for a non-printable character?

[KiYugadgeter]

I am reading kilo code for learning C language.
In line551, allocating 9 bytes memory for one non-printable character.
Why 9 bytes memory need for a non-printable character?

And nonprint variable is only initialized to 0 at line 543, and it is not assigned to other value.
So I think nonprint is not useful at line 551.
What's the meaning of this?

row->render = malloc(row->size + tabs*8 + nonprint*9 + 1);

[h4child]

I don't know!
But this already been removed https://github.com/practicalswift/openemacs/commit/469aadcb984ab693fe4a3cf9925790d0cf621f66 FORK

[dirkf]

The author probably intended to display non-printing characters something like <CTRL-D>. However ? is actually meant to be used, so the correct width is 1.