Unicode of Death 2.0

Manish Goregaokar via Unicode unicode at unicode.org
Fri Feb 16 12:44:29 CST 2018

FWIW I dissected the crashing strings, it's basically all <consonant,
virama, consonant, zwnj, vowel> sequences in Telugu, Bengali, Devanagari
where the consonant is suffix-joining (ra in Devanagari, jo and ro in
Bengali, and all Telugu consonants), the vowel is not Bengali au or o /
Telugu ai, and if the second consonant is ra/ro the first one is not also
ra/ro (or ro-with-line-through-it).



On Thu, Feb 15, 2018 at 10:58 AM, Philippe Verdy via Unicode <
unicode at unicode.org> wrote:

> That's probably not a bug of Unicode but of MacOS/iOS text renderers with
> some fonts using advanced composition feature.
> Similar bugs could as well the new advanced features added in Windows or
> Android to support multicolored emojis, variable fonts, contextual glyph
> transforms, style variants, or more font formats (not just OpenType); the
> bug may also be in the graphic renderer (incorrect clipping when drawing
> the glyph into the glyph cache, with buffer overflows possibly caused by
> incorrectly computed splines), and it could be in the display driver (or in
> the hardware accelerator having some limitations on the compelxity of
> multipolygons to fill and to antialias), causing some infinite recursion
> loop, or too deep recursion exhausting the stack limit;
> Finally the bug could be in the OpenType hinting engine moving some points
> outside the clipping area (the math theory may say that such plcement of a
> point outside the clipping area may be impossible, but various mathematical
> simplifcations and shortcuts are used to simplify or accelerate the
> rendering, at the price of some quirks. Even the SVG standard (in constant
> evolution) could be affected as well in its implementation.
> There are tons of possible bugs here.
> 2018-02-15 18:21 GMT+01:00 James Kass via Unicode <unicode at unicode.org>:
>> This article:
>> https://techcrunch.com/2018/02/15/iphone-text-bomb-ios-mac-
>> crash-apple/?ncid=mobilenavtrend
>> The single Unicode symbol referred to in the article results from a
>> string of Telugu characters.  The article doesn't list or display the
>> characters, so Mac users can visit the above link.  A link in one of
>> the comments leads to a page which does display the characters.
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