Re: [9fans] SO for plan9?

["Douglas A. Gwyn" <DAGwyn@null.net>]

Tom Duff wrote:
> Shared libraries are the work of the devil,
> the one true sign that the apocalypse is
> at hand.  Seriously, they're good for two
> things, first for plug-in features, which
> in plan 9 are often better handled by 9P
> servers (obviously not always, for example
> if there's an otherwise unachievable latency
> or throughput requirement), and second for
> giving third parties permission to break your
> code after you've shipped it.  I am stunned
> and amazed that anybody that pays salary to
> customer service reps would ever consider
> using shared libraries.

The two usual selling points are that installed
applications benefit from bug fixes in the shared
libraries (e.g. the standard C runtime library),
and that it saves a *lot* of disk space, especially
when big libraries are involved, as in X11.

There are a lot of things wrong with shared libraries
(or sometimes just with particular implementations);
for one thing they make it fairly easy to break
security; suppose a privileged process checks that
you are allowed to perform some action then invokes
a usually innocuous library function that you have
prearranged in your substitute shared library (easy
to do in Plan 9 where you own your name space) to
perform some other action that you would not normally
have been permitted to do.  I've seen this in set-UID
root UNIX programs (just found another yesterday) on
systems such as Solaris where you can affect the
runtime library directory search order (LD_*_PATH);
it is easy to make such a program fire up a /bin/sh
with inherited UID 0, which allows you to do anything
at all!