[XeTeX] XeTeX terminates with inscrutable diagnostic "!Emergency stop"

[Ken Moffat]

On Mon, Jul 29, 2024 at 08:57:04AM -0700, Andy Black wrote:
> (Sorry, I don't know how to respond to an email when using the digest mode,
> so I'm sending a response this way.)
> 
> I have gotten this message with XeLaTeX on both Windows and Linux when TeX
> is trying to hyphenate a word that has a character not in the normal set of
> characters for the language of the document.
> 
> For example, the document is written in Spanish and is set to use the
> Spanish hyphenation rules.  There is a word in the prose being processed
> that has a saltillo character in it (U+A78C).  My guess is that when TeX
> tries to hyphenate this word, hyphenation fails and the result is this
> emergency stop message.  If one either adds a hyphenation exception for this
> word (via adding it to the list in \hyphenation{}) or if one encloses it
> within an \mbox{}, then one does not get the emergency stop.
> 
> For some reason, this does not seem to happen on MacOS X.
> 
> --Andy Black

Interesting - on Linux I am used to pretending that everything is in
English (e.g. for languages where polyglossia either has nothing
(Maltese), or (for e.g. Cyrillic languages) needs an OpenType
tag which the font lacks) and watching text overflow.

But I don't recall seeing that error re being unable to hyphenate.
(Hope I'm not pushing my luck!)

ĸen
-- 
Voluntary positions are like garden bindweed: untended, they will
fill any void you might have.           -- James Max