[XeTeX] XeTeX segmentation faults

[Musa Furber]

Somdeva offered

> %
>  %Diatop lets you put one character (or accent) above another
>   
> \def\diatop[#1|#2]{{\leavevmode\setbox1=\hbox{{#1{}}}\setbox2=\hbox{{#2 
> {}}}%
>  \dimen0=\ifdim\wd1>\wd2\wd1\else\wd2\fi%
>  \dimen1=\ht2\advance\dimen1by-1ex%
>  \setbox1=\hbox to1\dimen0{\hss#1\hss}%
>  \rlap{\raise1\dimen1\box1}%
>  \hbox to1\dimen0{\hss#2\hss}}}
>  %
>  %Redefinitions of \d{}
>  \def\d#1{\smash{\diatop[\raise-.55em\hbox{\hskip.125em.}|#1]}}
>  %

for putting a dot diacritic below letters.

The .125em in the last line ensures that the dot is placed in the right  
place for Hoefler Text.

Most of the time I use the above macro with italic text. Changing the  
.125em to -.125em puts the dot in a reasonable place. Unfortunately,  
Hoefler italics use slightly different letter forms at the end of  
words, which looks bad in the middle of words.

So I have two questions:

Is there any way to indicate that this is not the end of the word?

Is it possible to rewrite the \def\d#1... macro so that an \hskip of  
.125em is used for regular text and -.125em for italics?

Man thanks to you all,
Musa