En Fri, 02 May 2008 00:26:38 -0300, grbgooglefan <[EMAIL PROTECTED]>
escribió:
On Apr 22, 7:54 am, "Gabriel Genellina" <[EMAIL PROTECTED]>
wrote:
If you have a C function that receives a PyCObject, just include the
relevant headers (cobject.h) and you can retrieve the original pointer
using PyCObject_AsVoidPtr:
This works. But only once, means if I try to use this object second
time in Python function it causes crash.
What I am doing in my program is that I am putting STL map in a
structure & passing that structure as object to a Python function
alongwith other agurments of that Python function. This briefly as
below:
// In pyinterface.h file:---
typedef hash_map<char*,int> Elements;
typedef hash_map<char*,Elements*,StringHash,eqstr>
PerExchGroupsElementsTable;
typedef struct capsule {
PerExchGroupsElementsTable* refgrps;
} *pcapsule;
// In pyinterface.cpp file:---
numvars = // value set depending on number of variables of that python
function
PyObject *pTuple = PyTuple_New(numvars);
// Set variables as below:
for(nCtr = 0; nCtr < numvars; nCtr++){
slot = prul->pVarLst[nCtr].slot;
ndtyp = ordvars[slot].dtype;
switch(ndtyp){
case(INT_T):
PyTuple_SetItem(pTuple,nCtr,PyInt_FromLong(ordvars[slot].nvalue));
break;
case(FLOAT_T):
PyTuple_SetItem(pTuple,nCtr,PyFloat_FromDouble(ordvars[slot].fvalue));
break;
case(STRING_T):
PyTuple_SetItem(pTuple,nCtr,PyString_FromString(ordvars[slot].cvalue));
break;
default:
printf("\nUnknown data type [%d] for %s\n",ndtyp,prul-
pVarLst[nCtr].var);
bUnknownDataType = true;
break;
}
if(bUnknownDataType){
ret = -1;
break;
}
}
// Then set the C++ object as below:
if(ret == 0){
capsule grpob;
if(pGroups){
grpob.refgrps = pGroups; // pGroups is pointer to
PerExchGroupsElementsTable map & is global.
int ret = PyTuple_SetItem(pTuple,
(numvars-1),PyCObject_FromVoidPtr((void *)&grpob, NULL));
}
This look suspicious - what if !pGroups? You can't leave a tuple item
uninitialized - if you create a tuple with PyTuple_New(3), then you have
to fill the 3 items.
And beware of that local variable grpob - you're using a pointer to it,
and it won't be valid when execution goes out of this block. You must
ensure that nobody stores a reference to it.
And you should decref the tuple even if this block isn't executed.
PyObject *ptr = PyObject_GetAttrString(_pPyModule,fname);
if(PyErr_Occurred() || *ptr == NULL){
printf("PyObject_GetAttrString failed:%s",fname);
return;
}
if(!PyCallable_Check(*ptr)){
printf("%s not a callable Python code\n",fname);
Py_XDECREF(*ptr);
*ptr = NULL;
return;
}
All those *ptr should be ptr (the compiler should issue a lot of warnings,
I presume?)
What happens is that when Python function TSE581 gets called from my C
Program via PyObject_CallObject (as shown at top of this post), co1
function works fine & can access the map pointer properly.
But when next function like1 gets called, crash happens.
My queries are & things on which I need help are:
1) Is there anything wrong I am doing when I am passing the C-Object
from my C++ code->Python -> C++ code again?
I see nothing obviously wrong, except the above notes. If you get warnings
from the C++ compiler, try to fix all of them.
2) Am I missing to increase or decrease the reference count somewhere.
In case of error you exit early but without releasing some existing
objects. (Sometimes a goto statement *is* the right thing to do)
3) I dont want map pointer to be ever freed because it is Process
level data structure & requried at every execution of these Python
functions. How do I avoid its cleanup when it gets passed to Python &
Python cleans up those objects.
Python will do nothing with the pointer inside a PyCObject - unless you
want to, and pass a cleanup function as the second argument to the
PyCObject constructor.
--
Gabriel Genellina
--
http://mail.python.org/mailman/listinfo/python-list
