feature or useful bug?

Vassili Dzuba vassilidzuba at nerim.net
Tue Jun 24 11:00:00 PDT 2003


On Mon, 23 Jun 2003 18:06:37 -0600
Izzy <l at nowhere.no> wrote:

> Oh! So it's a _feature_ of the XML spec.  I have to admit, my knowledge of
> XML is limited.  Playing with ALFS profiles is the closest I've come to
> doing anything XML.  It is good to hear that I should be able to depend on
> this feature in the future.  I was worried some one would report it as a
> bug and render my profiles broken! :(
> I'm guessing the XML processor described above is part of nALFS.  Perhaps
> having it issue workings, at the users option, would be useful.

nALFS uses libxml2 to parse the profiles.
You can find it at http://xmlsoft.org/
>From that page :

"Libxml2 is the XML C parser and toolkit developed for the Gnome project.
 XML itself is a metalanguage to design markup languages, i.e. text language 
where semantic and structure are added to the content using extra "markup"
 information enclosed between angle brackets. HTML is the most well-known 
markup language. Though the library is written in C a variety of language 
bindings make it available in other environments.

Libxml2 is known to be very portable, the library should build and work
 without serious troubles on a variety of systems (Linux, Unix, Windows,
 CygWin, MacOS, MacOS X, RISC Os, OS/2, VMS, QNX, MVS, ...)

> On a related note, while experimenting with this feature, I HAVE found a
> bug!  Creating a circular reference causes nALFS to segfault and dump core. 
> I know, it was a stupid mistake on my part, but it should cause nALFS to
> insult me for being so stupid, not dump core for no obvious reason!
> Although this could be considered an insult :)
> To illustrate, here's a simple example that will cause the coredump I've
> discovered:
> <!-- start.xml -->
> <!DOCTYPE alfs [
> <!ENTITY segfault SYSTEM "segfault.xml">
> ]>
> <alfs version="3.0">
> &segfault;
> </alfs>
> ----------------- 8< -----------------------
> <!-- segfault.xml -->
> &segfault;
> -------------------- 8< --------------------
> ...Izzy

Well, I assumes it's a problem with libxml2 as entity resolution
is done at that level, I think.

Vassili Dzuba
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