> Investigating further, the simple hello world program will compile
> and link fine provided I dont have a line like
> #include "stdio.h"
> in it.

Personally, I've always used #include <stdio.h>
I don't know whether this should make loads of difference though.

> If I have that line the compiler barfs, gives a core dump and prints
> a backtrace.

What does it say exactly?  (For the "Hello world" example)

> This happens if I am logged in as root or as another user.
> 
> I have checked the permissions in /usr/include/stdio.h
> and the owner and group are bin. Root is listed in /etc/group as
> a member of bin.
> 
> This looks like a mess up in my file permissions etc.

I could be wrong, but I wouldn't have expected file permissions to be a
problem if you're root.  (Feel free to put me straight on that one,
because I haven't exactly tested it...)

HTH,
David.