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Date: Wed, 25 Feb 2009 19:02:47 -0500 (EST)
From: Daniel Eischen <deischen@freebsd.org>
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Cc: kan@freebsd.org, freebsd-hackers <freebsd-hackers@freebsd.org>
Subject: Re: How to change an interface?
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On Wed, 25 Feb 2009, Xin LI wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi,
>
> Just wanted to confirm that the following procedure to change an
> existing interface:
>
> - Remove the symbol in question from all previous FBSD_1.* namespaces
> with their corresponding Symbol.map files;
>
> - Add the new symbol into latest FBSD_1.* namespace, say, FBSD_1.1 for
> now, into corresponding Symbol.map files;
>
> - Create a new file containing the compatibility shims with prefix __
> and suffix of something indicating its obsoleteness, e.g. _44bsd.  For
> instance, for function foo(), the shim function would be called
> __foo_44bsd();
>
> - At the tail of the shim file, add glues for the old symbols like this:
>
> __sym_compat(foo, __foo_44bsd, FBSD_1.0);
>
> - Double check to make sure that new .so would work with old binaries.
>
> Is that correct?

Yes, I believe that is correct.  I also think that
the awk script that processes the Symbol.map files
will also warn you if the symbol is multiply declared.

-- 
DE