Re: libtool versioning and ABI

[Bob Friesenhahn]

On Thu, 6 Aug 2009, Michel Briand wrote:
> Personally I've always seen interface as a contract.
> A contract between a library writer and library user.

The API is the compile-time contract and the ABI is the run-time 
contract.

> Since it's a contract, ABI changes fall into the contract agreement. 
> So why bother with complex versionning and error-prone version 
> manipulations with substraction

This is supposed to make things easier.

> The difficult, and somehow messy, scheme of libtool versioning is
> boring and uneasy : developers do not understand this different way
> that overlap with the classical, natural and contractual scheme (X.Y.Z
> that one can still use with the -release flag) ; and this create
> additional work to handle package version (official, classical) in
> parallel with libtool -version-info scheme.

The goal is to allow libraries to be updated without needing to 
rebuild all applications which link against a library with that name. 
There is also a goal to allow incompatable libraries to live side by 
side so that applications which need different libraries can live on 
the same system.

> Or I'm completely wrong.... but the documentation lacks some clues
> about what is this all about ;)))

Libtool did not invent these issues.  Different operating systems 
provide varying capabilities and methods for dealing with library 
versions.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/