[HarfBuzz] HB_CLOSURE_MAX_STAGES (was: harfbuzz: Branch 'master')

[Richard Wordingham]

On Wed, 1 Aug 2018 17:31:06 -0700
Behdad Esfahbod <behdad at behdad.org> wrote:

> On Mon, Jul 30, 2018 at 6:21 PM, Richard Wordingham <
> richard.wordingham at ntlworld.com> wrote:  
> 
> > On Mon, 30 Jul 2018 17:04:42 -0700
> > Behdad Esfahbod <behdad at behdad.org> wrote:

> > > It's impossible to hit that limit...  Ok, it would be impossible
> > > if we increase it to 32.  I'll do that.  

> > That'll probably work, but I'm now intrigued.  Why have a limit that
> > will never be hit?  Are you just catering for HarfBuzz's logic
> > simply going badly wrong in very unusual circumstances?

> Yes, simply as defense against malicious fonts and how the subsetter's
> glyph-closure routine can be tricked to collect (way) more glyphs than
> shaper can actually reach.

But if the limit is never hit, then the defence is never used, and so
it may as well not be there.  Or is it meant to initimidate
designers of malicious fonts who study Harfbuzz?

Richard.