[PyQt] SIP default exception handler

[Sébastien Petitdemange]

Hi,

We have tested your snapshot code and it works as expected. In fact, we
had a rather "obscure" problem where our exceptions were thrown in our
library, but it was not seen by your specific catch route. After a lot
of research, we saw that the Python (distutils) Makefile hides by
default the library symbols, except the "init<Module>" function. It
seems that this filtering also affect weak symbols with default values,
and we believe that this avoided the try ... catch block to properly
identify in run-time the good exception type id. The solution we found
was to specify export_all=True in the Module Makefile.

However, we have also seen a problem with dynamic parameter allocation.
In the example below, the /Out/ std::string buffer parameter is created
by sip. However, inside of our /Default/ exception handler or even the
catch (...) handler, the object is not deleted.

Do you have an idea of what could be happening?

Thanks again,

SEB


In the sip file:
================

class SerialLine : HwSerialLine
{
...
        virtual void read( std::string& buffer /Out/, int max_len,
                           double timeout=HwSerialLine::TimeoutDefault );
...
};

The generated code:
===================

extern "C" {static PyObject *meth_Espia_SerialLine_read(PyObject *,
PyObject *);}
static PyObject *meth_Espia_SerialLine_read(PyObject *sipSelf, PyObject
*sipArgs)
{
    int sipArgsParsed = 0;
    bool sipSelfWasArg = (!sipSelf || sipIsDerived((sipSimpleWrapper
*)sipSelf));

    {
        std::string * a0;
        int a1;
        double a2 = HwSerialLine::TimeoutDefault;
        Espia::SerialLine *sipCpp;

        if
(sipParseArgs(&sipArgsParsed,sipArgs,"Bi|d",&sipSelf,sipType_Espia_SerialLine,&sipCpp,&a1,&a2))
        {
            a0 = new std::string();

            Py_BEGIN_ALLOW_THREADS
            try
            {
            (sipSelfWasArg ? sipCpp->Espia::SerialLine::read(*a0,a1,a2)
: sipCpp->read(*a0,a1,a2));
            }
            catch (Exception &sipExceptionRef)
            {

                Py_BLOCK_THREADS
#line 18 "../common/sip/Exceptions.sip"
        const char *detail = sipExceptionRef.getErrMsg().c_str();
        PyErr_SetString(sipException_Exception, detail);
#line 528 "siplimaEspiaSerialLine.cpp"

                return NULL;
            }
            catch (...)
            {
                Py_BLOCK_THREADS

                sipRaiseUnknownException();
                return NULL;
            }
            Py_END_ALLOW_THREADS

            return sipConvertFromNewType(a0,sipType_std_string,NULL);
        }
    }

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

    return NULL;
}


Sébastien Petitdemange wrote:
> Phil Thompson wrote:
>> On Thu, 29 Oct 2009 10:08:33 +0100, Sébastien Petitdemange
>> <sebastien.petitdemange at esrf.fr> wrote:
>>> Hi,
>>>
>>> We are developing a C++ library that uses a single exception class
>>> (Exception) for throwing errors.
>>>
>>> When wrapping the library with sip, we use the -e command line to
>>> activate the try/catch code on each C++ call.
>>>
>>> However, our C++ code does not include the "throw(Exception)" modifier
>>> on each class method, because virtually any method can throw this
>>> exception, and it would be quite heavy to add it on every declaration.
>>>
>>> In this scenario, sip (v4.7.9) just include a default try {} catch (...)
>>> { sipRaiseUnknownException }, so Python reports "Exception: Unknown".
>>>
>>> Is there a way to specify a default exception handler to sip, so the
>>> generated code in this case would like something like:
>>>
>>>   try {
>>>       // C++ call
>>>   } catch (OurDefaultException& e) {
>>>       ...
>>>       sipRaiseClassException(sipclass_OurDefaultException ... );
>>>   } catch (...) {
>>>       sipRaiseUnknownException();
>>>   }
>> I've added support for a /Default/ exception annotation in tonight's
>> snapshot. Untested - let me know if it's not quite right.
>>
>> Phil
>>
> 
> Thanks a lot, I'll test that and let you know.
> 
> SEB
> 
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