Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <[email protected]> · Thu, 9 Jan 2020 11:50:55 -0800

On 1/9/20 11:10 AM, J. Lewis Muir wrote:
> On 01/09, Michael Davidsaver via Tech-talk wrote:
>> On 1/9/20 12:47 AM, Wang Xiaoqiang via Tech-talk wrote:
>>> I assume this ABI checking can be one additional step in the CI script, using tools like abi-compliance-checker. It could then be used as a guideline in development. e.g. attached is a generated report of pvAccess library between 7.0.2 and 7.0.3.
>>
>> I usually give a small sigh when I read "ABI compatibility" because it's
>> actually not as well defined and clear cut as you might think.  (especially
>> wrt. c++)
>>
>> When this has come up in the past, it has been difficult to convince those
>> arguing in favor of the difficulty.
> 
> Certainly I agree that maintaining ABI compatibility with C++ is much
> harder than with C, but I still think it's doable. 

I'm sorry, but I can't help but chuckle at your reply, which is _exactly_
what has been said in every previous discussion.

I concede that MS with it's army of devs., or Qt which it's history,
can design and maintain ABI compatible libraries.

The question has never been if it were possible, but rather who would do
this work for Base?

Thus my challenge (which you have chosen not to quote)

> Please identify all ABI changes made between 3.14.12.7 and 3.14.12.8
> and note those which are "incompatible".

> Microsoft has many
> C++ libraries, and they've managed to do it.  KDE and Qt similarly have
> managed to do it.  There are resources that attempt to explain changes
> you can and cannot make if you want to maintain ABI compatibility such
> as [1], [2], and [3] which I found just now with a web search.  And then
> there are the analysis tools to help catch mistakes.  I'm not saying it
> would be trivial, but so far I haven't seen evidence that it would be
> extremely difficult.
> 
> Lewis
> 
> [1]: https://www.youtube.com/watch?v=PHrXGHDd9no
> [2]: https://events.static.linuxfound.org/sites/events/files/slides/Binary_Compatibility_for_library_devs.pdf
> [3]: https://community.kde.org/Policies/Binary_Compatibility_Issues_With_C%2B%2B
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System