SIP: Virtual pure method with std::function

[Phil Thompson]

On 06/04/2021 13:24, Julien Cabieces wrote:
> Hi,
> 
>> You need to provide the C++ signature in [] after the Python 
>> signature.
>> See the example in this section...
> 
> I change the signature in the sip file like this
> 
> virtual MyObject *doThings( const QString &filePath, const QUrl &url,
> SIP_PYCALLABLE / AllowNone / ) = 0 [MyObject * ( const QString &, const
> QUrl &, const ErrorCallback & )];
> 
> and define the ErrorCallback this way in my header
> 
> typedef std::function< void ( const QString & ) > ErrorCallback;
> 
> It fails later with this error
> 
> sip_corepart0.cpp:21379:193: error: unknown type name 'ErrorCallback'
> 
> my header file is included later (line 49811) in cpp file produced by
> sip, so it's normal it doesn't know yet the ErrorCallback type.
> 
> If I get rid of the typedef definition and put the std::function
> directly in the sip signature, sip fails with a syntax error. It looks
> like it comes from the parenthesis around "const QString &".
> 
> Any idea?

SIP doesn't implement a full C++ parser and there will be some 
constructs that it can't handle, in this case the arguments to the 
std::function template. (Maybe putting a dummy name after the void would 
work.)

A separate issue might be that SIP is being too aggressive when parsing 
the C++ signature and maybe it could/should not try to resolve 
ErrorCallback and leave it to the C++ compiler to determine if it has a 
proper definition.

For the moment I can't suggest anything other than not using 
std::function.

Phil