On Thursday 03 January 2008, grbgooglefan wrote:
> I have a following C++ code which uses PyObject_CallObject to evaluate
> expressions dynamically. This code sets the input parameters for the
> function also dynamically. After calling this function 4 times (with
> these shown values), PyObject_CallObject causes application to crash
> in frame_dealloc.
> 1) Can some one please help me understand why is this crash happening
> in frame_dealloc & how to solve it?
> 2) Is there anything wrong I am doing about incrementing or
> decrementing the reference counts of the object passed to
> PyObject_CallObject?
Yes.
> 3) Is it because of the big value (2299265.500000) I am trying to
> convert from double to float using PyFloat_FromDouble?
>
> //========================= code reduced for readability
> ===============
> switch(ndtyp){
> case(INT_T):
> {
> printf("PyInt_FromLong val %d, var %s
> \n",inputVar.nionum,pEvalFunc->pExprVarsArray[nCtr].szVarName);
> val = PyInt_FromLong(inputVar.nionum);
> break;
> }
> case(LONG_T):
> {
> printf("PyLong_FromLong val %ld, var %s
> \n",inputVar.lionum,pEvalFunc->pExprVarsArray[nCtr].szVarName);
> val = PyLong_FromLong(inputVar.lionum);
> break;
> }
> case(FLOAT_T):
> {
> printf("PyFloat_FromDouble val %f, var %s
> \n",inputVar.fionum,pEvalFunc->pExprVarsArray[nCtr].szVarName);
> val = PyFloat_FromDouble(inputVar.fionum);
> break;
> }
> case(DOUBLE_T):
> {
> printf("PyFloat_FromDouble val %f, var %s
> \n",inputVar.dionum,pEvalFunc->pExprVarsArray[nCtr].szVarName);
> val = PyFloat_FromDouble(inputVar.dionum);
> break;
> }
> case(STRING_T):
> {
> printf("PyString_FromString val %s, var %s
> \n",inputVar.ioString,pEvalFunc->pExprVarsArray[nCtr].szVarName);
> val = PyString_FromString(inputVar.ioString);
> break;
> }
> default:
> printf("Unknown data type [%d] for %s\n",ndtyp,pEvalFunc-
>
> >pExprVarsArray[nCtr].szVarName);
>
> }
> if(!val){
> ret = -1;
> printf("Failed to convert %d %s to PyObject\n",ndtyp,pEvalFunc-
>
> >pExprVarsArray[nCtr].szVarName); fflush(stdout);
>
> Py_XDECREF(pTuple);
> break;
> }
> PyTuple_SetItem(pTuple, nCtr, val);
> Py_XDECREF(val);
Don't do this - PyTuple_SetItem() steals a reference to val.
> }
> // all variables are set, call Python function
> Py_XINCREF(pTuple);
Why do this?
> PyObject *pResult = PyObject_CallObject(pEvalFunc-
>
> >pPyEvalFunction,pTuple);
>
> Py_XDECREF(pTuple);
Why do this?
> if(PyErr_Occurred()){
> PyErr_Print();
> } else {
> char* plevel = NULL;
> if(NULL != (plevel = PyString_AsString(pResult))){
> ret = 0;
> sprintf(szEvalResult,"%s",plevel);
> }
> }
> Py_XDECREF(pResult);
pTuple will now have the same number of references as when you started the
above code, so you may want to Py_DECREF() it.
Phil
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