Re: [dpdk-dev] Add DSO symbol versioning to supportbackwards compatibility

[Neil Horman <nhorman@tuxdriver.com>]

On Sat, Dec 20, 2014 at 04:01:35PM -0500, Neil Horman wrote:
> GI: [PATCH 1/4] compat: Add infrastructure to support symbol versioninBI
> develops and changes quickly, which makes it difficult for
> applications to keep up with the latest version of the library, especially when
> it (the DPDK) is built as a set of shared objects, as applications may be built
> against an older version of the library.
> 
> To mitigate this, this patch series introduces support for library and symbol
> versioning when the DPDK is built as a DSO.  Specifically, it does 4 things:
> 
> 1) Adds initial support for library versioning.  Each library now has a version
> map that explicitly calls out what symbols are exported to using applications,
> and assigns version(s) to them
> 
> 2) Adds support macros so that when libraries create incompatible ABI's,
> multiple versions may be supported so that applications linked against older
> DPDK releases can continue to function
> 
> 3) Adds library soname versioning suffixes so that when ABI's must be broken in
> a fashion that requires a rebuild of older applications, they will break at load
> time, rather than cause unexpected issues at run time.
> 
> 4) Adds documentation for ABI policy, and provides space to document deprecated
> ABI versions, so that applications might be warned of impending changes.
> 
> With these elements in place the DPDK has some support to allow for the extended
> maintenence of older API's while still allowing the freedom to develop new and
> improved API's.
> 
> Implementing this feature will require some additional effort on the part of
> developers and reviewers.  When reviewing patches, must be checked against
> existing exports to ensure that the function prototypes are not changing.  If
> they are, the versioning macros must be used, and the library export map should
> be updated to reflect the new version of the function.
> 
> When data structures change, if those structures are application accessible,
> apis that accept or return instances of those data structures should have new
> versions created so that users of the old data structure version might co-exist
> at the same time.
> 
> Note it was requested that this series be delayed until DPDK 2.0, so this is a
> repost, now that DPDK 1.8 has been tagged.
> 
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> CC: Thomas Monjalon <thomas.monjalon@6wind.com>
> CC: "Richardson, Bruce" <bruce.richardson@intel.com>
> CC: "Robert Love" <robert.w.love@intel.com>
> 
> 
Ping Thomas....