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From: Rich Johnson (rjohnson_at_[hidden])
Date: 2006-01-26 19:26:50

On Jan 26, 2006, at 11:58 AM, Noel Yap wrote:

> Hmm, I've been thinking about this problem but from a different
> perspective.
> First, some definitions:
> - patch release: the new component is link and load compatible with
> the old one; clients might need to relink or reload
> - minor release: the new component is compile compatible with the old
> one; clients might need to recompile
> - major release: the new component isn't compatible with the old one;
> clients might need to modify code
> Given the above, a mapping can be made of changes to source to one of
> the above. I suppose if a component developer follows the above, one
> could write a class that could easily figure out whether or not a
> certain M.m.p update is backwards compatible with another.
> Also, what really counts are changes to header files. More
> specifically, changes to published header files (ie header files that
> are installed so as to be usable by other components).

I LIKE the crispness of your functional definitions. They suggest
that there may exist an algorithm determining the ''order'' of a change:
- Any change in the interface base class is _at least_ a minor release.
- Any change in an implementation derived class is _at most_ a patch
- Any change in the semantics of the base class interface is _at
least_ a major release.
- Version stamp can probably be generated by configuration control
(i.e. CVS);
- Version stamp can probably be used as a _signature_ of the module's

FWIW, a "compiler compatibility" is probably required when dealing
with separately compiled modules.

Applying the definitions to dynamically loaded libraries where we're
_always_ relinking; we come up with:
- if patch release; accept
- if minor release; reject (you _might_ scoot by with some changes;
but why risk it?)
- if major release; reject
- if compiler incompatible; reject (of course).

Dynamically loaded modules could supply a ''well known'' C function
to access their version stamp (or otherwise determine compatibility)
prior to instantiating any dynamically allocated objects.

Now you've got me thinking....

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