[XeTeX] xetex crash: interaction between interchar and linebreaklocale mechanisms

Mike Maxwell mmaxwell at umd.edu
Sat Sep 9 21:39:51 CEST 2023

Back in 2018, I was trying to use LuaTeX to typeset multiple scripts. 
(We needed its capability to tell you where on the page bounding boxes 
were.)  LuaTeX worked ok for some scripts, but failed for example for 
Tamil, where glyphs don't always appear in the same order on the page as 
their underlying characters do.  This sort of issue arises with many 
Indic scripts, and something similar would probably happen with Burmese, 
which in some ways is an even more complex script than other Indic ones.

At the time, I recall the LuaTeX developers saying they were not 
interested in solving this issue, and that instead script-specific 
libraries should be developed.  (I'm going by memory here, I don't have 
links to that discussion, although see here: 

Since that time, Khaled Hosny has conducted an "experiment" (his term) 
in using HarfBuzz in LuaTeX 
(https://tug.org/TUGboat/tb40-1/tb124hosny-harfbuzz.pdf, as reported in 
2019), and Kai Eigner also did similar work 
(https://github.com/tatzetwerk/luatex-harfbuzz).  The LuaTeX wikipedia 
page says LuaTeX "includes" the HarfBuzz engine (and links to the above 
two reports).

I haven't tried LuaTeX in recent years, but it sounds like if you ran 
Burmese through it and used the HarfBuzz shaper instead of the 
default(?) shaper, it might work for Burmese.

I'll be interested to hear what you find.

     Mike Maxwell

On 9/9/2023 2:29 PM, Andrew Goldstone wrote:
> Thanks--it turns out that xelatex still segfaults if I attempt to 
> combine ucharclasses and \XeTeXinterwordspaceshaping=2 in a longer 
> document. I do think this is a bona fide xetex bug but don't have the 
> knowledge of the xetex source to trace it further.
> As for lualatex it seemed to have more trouble than xelatex with the 
> complex ligatures in Burmese. The lineation issues are a lower priority 
> for my colleague than simply being able to typeset his mixed-script 
> text, so I'll help him to a workaround with xetex, if no other 
> suggestions for fixes are forthcoming.
> All best,
> Andrew
> Sat, Sep 9, 2023 at 5:37 AM Ulrike Fischer <news3 at nililand.de 
> <mailto:news3 at nililand.de>> wrote:
>     Am Wed, 6 Sep 2023 10:40:16 -0400 schrieb Andrew Goldstone:
>      > I believe this is the same issue as was raised on StackExchange
>     in 2019
>      >
>     https://tex.stackexchange.com/questions/503498/trouble-with-stacked-consonants-burmese-script <https://tex.stackexchange.com/questions/503498/trouble-with-stacked-consonants-burmese-script>
>      > but I couldn't find any further discussion of a fix for the crash.
>     I don't think that there is a fix and the xetex development is
>     rather stale. Personally I would try with lualatex.
>     -- 
>     Ulrike Fischer
>     http://www.troubleshooting-tex.de/ <http://www.troubleshooting-tex.de/>

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