Subject: Re: Is setup.exe _supposed_ to delete the cygwin dll before attempting to run shell scripts?
From: Brian Dessent <[email-masked]>
To: [email-masked]
Date: Fri, 24 Sep 2004 15:06:46 -0700

Igor Pechtchanski wrote:

> It'll work for simple programs, but not for packages where preremove
> scripts erase files that are needed to run some programs from that
> package.  One example (not necessarily a perfect one) that comes to mind
> right away is the base-files package, where the preremove script will
> currently erase /etc/profile (so any script executing "bash -l" will not
> get the expected results).  I'm sure there are better examples...
> 
> FWIW, this is probably somewhat similar to the issue of circular
> dependencies of postinstall scripts -- there is no good general solution
> if we assume monolithic scripts.

Wouldn't the "proper" way to do this be to build the dependency tree
then remove packages in depth-first order, running each preremove before
removing each package list?

Example:

Dependency tree:

  A
 / \
B   C
     \
      D

So lets say you want to remove and then upgrade new versions of A, B, C,
and D.

You first get the depth-first order: D, C, B, A.

Then you run: preremove(D), remove-files(D), preremove(C),
remove-files(C), preremove(B), remove-files(B), preremove(A),
remove-files(A)

To install you do the same thing, except you'd do breadth-first and
you'd do postinstall(X) after each install-files(X).  (I know this is
not the current method, where all postinstalls are run in a batch at the
end.)

Brian

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