Re: [dpdk-dev] [PATCH 1/4] vhost: handle VHOST_USER_SET_LOG_BASE request

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2015-12-07 13:41, Panu Matilainen:
> On 12/07/2015 01:28 PM, Thomas Monjalon wrote:
> > 2015-12-07 08:29, Panu Matilainen:
> >> On 12/07/2015 01:07 AM, Thomas Monjalon wrote:
> >>> 2015-12-02 15:53, Panu Matilainen:
> >> The vhost ABI break was announced for DPDK 2.2 in commit
> >> 3c848bd7b1c6f4f681b833322a748fdefbb5fb2d:
> > [...]
> >> So the ABI process was properly followed, except for actually bumping
> >> LIBABIVER. Bumping LIBABIVER is mentioned in
> >> doc/guides/contributing/versioning.rst but it doesn't specify *when*
> >> this should be done, eg should the first patch breaking the ABI bump it
> >> or should it done be shortly before the next stable release, or
> >> something else. As it is, it seems a bit too easy to simply forget.
> >
> > I thought it was not needed to explicitly say that commits must be atomic
> > and we do not have to wait to do the required changes.
> 
> The "problem" is that during a development cycle, an ABI could be broken 
> several times but LIBABIVER should only be bumped once. So ABI breaking 
> commits will often not be atomic wrt LIBABIVER, no matter which way its 
> done.

If the ABI version has already been changed, there should be a merge conflict.
I think it's better to manage a conflict than forget to update the version.

> For example libtool recommendation is that library versions are updated 
> only just before public releases:
> https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html#Updating-version-info

Interesting link. It makes me think that we do not manage ABI break when
downgrading the library (case of only new API keeping the ABI number).

> > In this case, I've missed it when reviewing the vhost patches breaking the
> > ABI.