Deprecation of stuff

[David Woodhouse]

On Mon, 2019-09-02 at 08:38 +0200, Richard Levitte wrote:
> The dispute in PR https://github.com/openssl/openssl/pull/7853 has
> made it quote obvious that we have some very different ideas on when
> and why we should or shouldn't deprecate stuff.
> 
> What does deprecation mean?  Essentially, it's a warning that at some
> point in the future, the deprecated functionality will be removed.  I
> believe that part of the issue surrounding this is uncertainty about
> when that removal will happen, so let me just remind you what's
> written in our release strategy document:
> 
>   * No existing public interface can be removed until its replacement
>     has been in place in an LTS stable release. The original interface
>     must also have been documented as deprecated for at least 5 years.
>     A public interface is any function, structure or macro declared in
>     a public header file.
> 
> Ref: https://www.openssl.org/policies/releasestrat.html
> 
> I'd like to get this thread started with the following four questions,
> for as many of us to answer as possible:
> 
> 1. Why should we deprecate stuff
> 
> 2. Why should we not deprecate stuff
> 
> 3. When should we deprecate stuff
> 
> 4. When should we not deprecate stuff
> 
> Cheers,

(I know -project won't accept my mail; you can choose to include it in
a reply if you see fit).


I'd note that the question of *versioning* mechanisms is a very very
special case of "when to deprecate stuff". So much so as to almost make
it a completely separate question altogether.

My own favourite application is littered with checks on
OPENSSL_VERSION_NUMBER, and the occasional call to SSLeay() to check
for things that were fixed at runtime without an ABI change.

http://git.infradead.org/users/dwmw2/openconnect.git/blob/HEAD:/openssl.c
http://git.infradead.org/users/dwmw2/openconnect.git/blob/HEAD:/openssl-dtls.c

A change to the versioning scheme is very much more than just another
thing that's been deprecated; it's a change to the very mechanism by
which we handle those deprecations. Changing that (and by extension,
rapidly deprecating it) requires a lot more work on the part of
application authors who want their code to build against whatever
version of OpenSSL may be present on the platforms they need to
support.



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