feature or useful bug?

Izzy Blacklock izzyb at ecn.ab.ca
Sun Jun 22 00:39:34 PDT 2003


I've been experimenting with building some new profiles and discovered an 
unexpected behavior.  I accidently created an entity with the same name as 
another.  This didn't produce an error or warning as I would have expected.  
Instead it silently chose the first occurrence of the entity and ignored the 
future occurrence.  Somehow I don't think this is a _feature_ (at least I 
don't recall seeing it documented anywhere), but it occurred to me that it 
could be very useful behavior. 

One thing I've been experimenting with is trying to build profiles in such a 
way that they can be used either on their own, or as building blocks for 
other profiles.  In this way, a number of profiles from a variety of sources 
can be used to build a system with the desired features.  My hope is to come 
up with a system that makes profiles easier to build for specific needs and 
more practice to share with others.  One problem that I've run into is how to 
make a small change to a profile for a specific need, without needing to 
duplicate and modify the original.

For instance, what if I want to load Grub instead of lilo (I don't, this is 
just an example) using Naven's LFS4.0 profile included with nALFS?  To avoid 
duplicating and modifying the whole profile, I would create an alternate for 
LFS-4.0.xml, so I could create an alternate for entities/system, so I could 
specify an alternate for chapter6/lilo.xml to either load grub instead or do 
nothing if I had an different profile loading grub.

If I take advantage of this _bug_, all I need to do is create an alternate for 
LFS-4.0.xml (which I'm doing already so I can load other profiles) and load 
an entity which override anything I need to change, before loading the 
standard profile entities.  Besides being simpler, this approach isn't likely 
going to need modifying when you change to the LFS-4.1 profile once it comes 
out.

So, why am I telling you all this?  Well, besides hoping it is usefull to 
others, I want to make sure that this _bug_ is considered a _feature_ in 
future development.  ie, I'd hate to see it get fixed! :)  It may be usefull 
however to cause a warning to be displayed unless a command line flag is set 
to ignore them.  That way, people wont get bitten if they accidently 
duplicate an entity name like originally happened to me.  It took my a little 
while to track down the problem when things weren't working as I expected! :(  

...Izzy

PS: I plan to eventually make my profiles available to anyone who is 
interested.  I'm currently working on an LFS-4.1 profile which uses this 
technique to override Naven's LFS-4.0 profile.  I'm installing a system with 
it right now. If all goes well, I'll make it available by request until I get 
around to putting up a web site it can call home.
 
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