Bug#391240: debian-policy: Please elaborate on cleaning up files outside the build dir

[Ian Jackson <ian@davenant.greenend.org.uk>]

Frank Küster writes ("Bug#391240: debian-policy: Please elaborate on cleaning up files outside the build dir"):
> "writing to the home directory" also includes creation of dotfiles,
> which some programs do when used the first time (and they keep "copies"
> of the site-wide conffiles there, which are not subject to conffile
> updating).  The problem with the TeX font cache has actually caused a
> FTBFS bug, and I've documented it in the TeX policy draft (pending
> upload).  However, many packages create documentation without directly
> using TeX, and therefore won't find the information in the TeX policy. 

Surely cache data is OK if the cache is functioning properly ?
That is, if the data which ends up in the cache doesn't cause any
difference in behaviour other than a speed increase.

I don't understand the TeX problem at all, but wouldn't it be a bug in
TeX if it caches things in a way that makes it break in the future ?

Ian.