I sent Hans the plain TeX example, but I don't think he did anything with it. Feel free to write him yourself if you want, or let's just forget the whole thing. Sorry for the noise. So many more important things to spend time on ...
I can't run anything on Windows, so no, I can't confirm :(. There's nothing post-TL25(or pre-TL25) that would affect this, as far as I know. Nothing serious has changed in the xetex sources in years, apart from the JP devs making it work better with over-BMP chars. Anyway, Hans was using the released TL25 binary. Thanks for looking into it so carefully. Guess there's nothing to be done.
P.S. If you have any time/interest in looking into things, just glancing over the open bug list shows a variety of things that presumably affect people's real-life output. Stacking diacritics (182), all the rtl stuff, etc. Unfortunately almost all the bugs are reported from "nobody" so it's hard to tell what might be important, i.e., from the latex team. P.P.S. There's also #185, where Ross Alexander sent in patches to purportedly "fix" an observable minute line breaking difference with the other...
This runs under initex. And it shows that the problem is apparently Windows-specific, as Hans is running on Windows. i get the same results for pdftex and xetex in tl25 on x86_64-linux, as you did. What's different in Akira's build is not something I want to delve into ... \catcode`\{=1 \catcode`\}=2 \catcode`\^=7 \newlinechar=`^^J \font\tenrm=cmr10 \tenrm \def\space{ } % \setbox0\hbox{\romannumeral 3910725} \message{^^J[3910725: \the\wd0 \space cf. 32722.85156pt]^^J} % \setbox0\hbox{\romannumeral...
Hello anonymous - thanks for your reply. If I thought anyone would ever actually debug xetex again, I'd ask Hans or figure out how to reproduce it outside of ConTeXt. Or figure out exactly how to run it in ConTeXt. As it is, there are far, far, more important bugs already submitted, so I'm not inclined to spent more time on this obscurity ...
strange behavior with large \romannumeral
I got tired of looking at this, so I wrote the little bit of shell code to simplistically guess the type of the list parameter to XawListChange. I just committed it to TL, r74082. Maybe it will work in practice? But I won't be surprised if I overlooked something that makes it fail. The diff is attached, I hope.
Thanks for the investigations, Paul. That sort of -D + cast does not look like it could work for TL. I still don't see a plausible fix short of a configure test :(.