Broken ABI in networkmanager-qt

[Harald Sitter]

On Tue, May 17, 2016 at 11:06 AM, Jan Grulich <jgrulich at redhat.com> wrote:
> Hi,
>
> we decided to drop WiMAX support in nm-qt when it's compiled against NM 1.2.0,
> but this seems to break binary compatibility when nm-qt was previously build
> against older NM version. I didn't realize this before that this could happen
> and now I'm not sure how fix that.
>
> We could either:
> 1) Revert the change removing WiMAX support, but that would break ABI
> compatibility one more time.
>
> 2) Keep it as it is and let packagers know about this problem and ask them to
> rebuild everything using nm-qt (plasma-nm, plasma-workspace) in case they
> already have NM 1.2.0.
>
> What do you think is a better option?

I am not sure how 1) would be an issue, or how it would break ABI
again for that matter.
If you add the relevant ABI back you are doing an ABI addition on top
of the effectively new ABI, and adding things generally is a binary
compatible change to both the original ABI (which would be back again)
as well as the new semi-broken ABI as it would simply expand to again
contain the removed ABIs. That said 1) is the better option. If one
has built on top of nm-1.2, binary compatibility would be restored as
the previous ABIs are back. If one hasn't built on top of nm-1.2,
nothing would change and it would be as though the binary incompatible
change never happened.

2) would imply that we disregard the frameworks ABI stability promise
which probably wouldn't be very nice. This option would also at the
very least require a so-version bump to communicate the breakage
properly.

HS