Re: Shared libs.

[Stephen Usher <Stephen.Usher@earth.ox.ac.uk>]

I've been following the shared lib discussion with some interest.

There is an easy way to solve the problem of local (to a process) variables.
Whatever you do you'll need stub routines to link to when you build the
executable, so why not get these to allocate all the variables in a block
and then pass a variable base pointer to the shared routine?

This would only have to be done once. The second, third and n'th time the
routine was called all that would be needed would be to pass the base
pointer to that shared routine.

The advantage is that this scheme is simple.. and hence it's likely to work.

The only problem you may have is if the program is pre-empted whilst inside
the shared routine, in which case we have to make sure that the routines are
fully re-entrant, say by using the current pid as a redirection pointer to
local variables or something (though this may need some help from the
kernel). Alternatively, you can make all the shared library calls atomic.
It's up to you.

Steve

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