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Re: Help with Qwt and PyQt-Qwt, C++ symbols

On 1 Jan 2018, at 22:49, Gudjon I. Gudjonsson <gudjon@gudjon.org> wrote:
> Hi Dima
> Thanks a lot. This is very helpful.
>> This generates the attached report. I guess the proposed patch changes
>> the layout of the vtable, so calls to virtual functions past the vtable
>> changes would break.
>> I can't tell what problem you're trying to solve since I can't tell how
>> you're trying to build PyQt-Qwt. What build errors are you seeing? How
>> can I see them? Can PyQt-Qwt be updated to live with the unpatched qwt?
> There are two problems.
> 1. I need do understand better if an update of the library (change in the symbols table)
>    requires a bump in the abi version or not.
>    You seem to have solved that problem.
> 2. I need to make PyQt-Qwt compile and work with the qwt library.
> The best solution is to fix the PyQt-Qwt code (SIP) but I haven't found out how to do that
> but by patching qwt, it works perfectly.
> Now I am updating Qwt to version 6.1.3 and if I want to add the patch, the time is right to do it
> but I want to be sure that the patch doesn't make problems for other users of the library.
> I hope this explains my problem :)

This whole patch seems extremely suspicious to me, and I'm wondering whether
there's an A/B problem here. You're trying to write a wrapper for a library, so
why do you need to patch the library itself to add pointless dummy
implementations for what are currently pure virtual functions (I would assume
the library authors made them pure virtual for a good reason)?


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