[PyKDE] Ivalid cast (PyKDE-snapshot20050316, GCC 4)

[Jim Bublitz]

On Friday 18 March 2005 11:27, Akos Polster wrote:
> I'm getting this error while compiling PyKDE-snapshot20050316 on
> Linux with GCC 4.0:
>
> sip/kdecore/kurl.sip: In function ‘PyObject*
> slot_KURL_List___add__(PyObject*, PyObject*)’:
> sip/kdecore/kurl.sip:348: error: invalid cast of an rvalue expression of
> type ‘QValueList<KURL>’ to type ‘const KURL::List&’
>
> The environment is:
>
>  - Python 2.4.0
>  - sip snapshot-20050317
>  - QT 3.3.4
>  - PyQt snapshot-20050311
>  - KDE 3.4.0
>  - GCC 4.0.0 20050310 (Red Hat 4.0.0-0.33)

Here's the code in question with the failing line indicated:

sip/kdecore/kurl.sip
============

        KURL::List           operator + (const KURL::List&);
%MethodCode
//returns (KURL.List)
//takes listToAdd | (KURL.List)
    Py_BEGIN_ALLOW_THREADS
==>>    sipRes = new KURL::List((const KURL::List&)((*sipCpp) + *a0));
    Py_END_ALLOW_THREADS
%End


Here's the generated C++ code:

kdecore/sipkdecorepart0.cpp
==================

static PyObject *slot_KURL_List___add__(PyObject *sipSelf,PyObject *sipArg)
{
==>> KURL::List *sipCpp = reinterpret_cast<KURL::List *>(sipGetCppPtr(
                   (sipWrapper *)sipSelf,sipClass_KURL_List));

	if (!sipCpp)
		return 0;

	int sipArgsParsed = 0;

	{
		const KURL::List * a0;

		if (sipParseArgs(&sipArgsParsed,sipArg,"J1",sipClass_KURL_List,&a0))
		{
			KURL::List *sipRes = 0;

#line 345 "sip/kdecore/kurl.sip"
//returns (KURL.List)
//takes listToAdd | (KURL.List)
    Py_BEGIN_ALLOW_THREADS
    sipRes = new KURL::List((const KURL::List&)((*sipCpp) + *a0));
    Py_END_ALLOW_THREADS
#line 19720 "sipkdecorepart0.cpp"

			return sipNewCppToSelf(sipRes,sipClass_KURL_List,SIP_SIMPLE|SIP_PY_OWNED);
		}
	}

	/* Raise an exception if the arguments couldn't be parsed. */
	sipNoMethod(sipArgsParsed,sipNm_kdecore_List,sipNm_kdecore___add__);

	return 0;
}

note that sipCpp is  of type KURL::List.

Here's the class declaration for KURL::List:

kdelibs-3.4.0/kdecore/kurl.h
==================

class KURL
{
  ...
  class KDECORE_EXPORT List : public QValueList<KURL>

And from Qt,  the copy constructor being used requires a 'const':

    QValueList ( const QValueList<T> & l )

I don't see where the cast is in error (but then my C++ skills aren't that 
great). 

I don't have gcc 4.0 to test against, so I have no way of pursuing this much 
farther. The easiest workaround would be to comment out the code fragment 
shown above from sip/kdecore/kurl.sip (you lose the + operator for 
KURL::List). The cast is there because it won't compile without it on gcc 3.3 
- it can't find a  "non-const" copy ctor to use, which is what sip generates 
without the cast.

Jim