[PyQt] SIP multiple inheritance with template base class

[Giuseppe Corbelli]

On 03/31/2018 12:57 PM, Phil Thompson wrote:
> On 30 Mar 2018, at 1:53 pm, Giuseppe Corbelli <corbelligiuseppe at mesdan.it> wrote:
>>
>> Hi all
>> for an ongoing project I am developing a Python interface for QCustomPlot.
>> You can find it at https://github.com/cowo78/QCustomPlot-PyQt5/tree/v2.0.0
>>
>> My first attempt with sip so look out for stupid mistakes.
>>
>> SIP 4.19.8, (Py)Qt 5.9.2 on linux/gcc 7.3
>>
>> I have the following hierarchy:
>>
>> template <DataType>
>> class QCPAbstractPlottable1D : public QCPAbstractPlottable, public QCPPlottableInterface1D /Abstract/
>> {
>> %TypeHeaderCode
>> #include <QCustomPlot/src/qcp.h>
>> #include "helper.h"
>> %End
>> { ... }
>>
>> typedef QCPAbstractPlottable1D<QCPBarsData> QCPAbstractPlottable1D_QCPBarsData;
>>
>> class QCPBars : public QCPAbstractPlottable1D_QCPBarsData
>> {
>> %TypeHeaderCode
>> #include <QCustomPlot/src/qcp.h>
>>
>> typedef QCPAbstractPlottable1D<QCPBarsData> QCPAbstractPlottable1D_QCPBarsData;
>> %End
>> ...
>> }
>>
>> Nevermind the helper.h include for a second. With this code the c++ generated for the QCPAbstractPlottable1D_QCPBarsData lacks a typedef.
>>
>> The typedef'ed template specialization produces sipQCustomPlotQCPAbstractPlottable1D_QCPBarsData.cpp which references the typedef itself (QCPAbstractPlottable1D_QCPBarsData) but it is not copied in the generated file. The helper.h just works around the issue by providing the relevant typedef.
>>
>> The full error can be reproduced by checking out branch v2.0.0 of https://github.com/cowo78/QCustomPlot-PyQt5.git and commenting out the #include "helper.h" directive.
>>
>> Something wrong in my approach or an obscure bug somewhere?
> 
> I'm not sure what the issue is that you are raising. Is it the fact that you have to provide the C++ typedef (and, if you do, it works Ok)? If you specify something in the .sip file it is assumed that this reflects something that is in the C++ code - and you need to provide it if it doesn't.

Well, I must admit the explanation wasn't that good.
The issue is that, even if I provide the typedefs, the generated code 
does not compile. The generated code for the explicit template 
specialization does not include the relevant typedef.

This is the compiler error:

sipQCustomPlotQCPAbstractPlottable1D_QCPBarsData.cpp:121:18: error: 
‘QCPAbstractPlottable1D_QCPBarsData’ in namespace ‘::’ does not name a type
          const  ::QCPAbstractPlottable1D_QCPBarsData *sipCpp;

Again, the error can be reproduced by checking out branch  v2.0.0 of 
https://github.com/cowo78/QCustomPlot-PyQt5.git and commenting out the 
#include "helper.h" directive in plottable1d.sip.

-- 
Giuseppe Corbelli