C Wrapper Function, crashing Python?
Java and Swing
codecraig at gmail.com
Wed Oct 12 09:31:06 EDT 2005
Antoon,
I just saw that to. I updated the code like so...
static PyObject *wrap_doStuff(PyObject *self, PyObject *args) {
// this will store the result in a Python object
PyObject *finalResult;
// get arguments from Python
char *result = 0;
char *in= 0;
char *aString = 0;
char *bString = 0;
MY_NUM *a = (MY_NUM *) PyMem_Malloc((20 * sizeof(MY_NUM) + 1); //
the array will be 20 long
MY_NUM *b = (MY_NUM *) PyMem_Malloc((20 * sizeof(MY_NUM) + 1); //
the array will be 20 long
int ok = PyArg_ParseTuple(args, "sss", &in, &aString, &bString);
if (!ok) return 0;
// do work to get a and b
// count - returns an int; GetVal - returns a MY_NUM * (a pointer
to a MY_NUM array)
a = GetVal(aString, count(aString, ","));
b = GetVal(bString, count(bString, ","));
// make function call, which returns a char *
result = doStuff(in, a, b);
// save result in Python string
finalResult = PyString_FromString(result);
// free memory
PyMem_Free(a);
PyMem_Free(b);
free(aString);
free(bString);
free(result);
// return the result as a Python string
return finalResult;
}
..as you can see, i malloc'ed memory, and free'd the memory. However,
I still have python crashing (after only 3 successful calls to
doStuff). And yes, doStuff is a plain C function...nothing related to
Python.
Antoon Pardon wrote:
> Op 2005-10-12, Java and Swing schreef <codecraig at gmail.com>:
> > static PyObject *wrap_doStuff(PyObject *self, PyObject *args) {
> > // this will store the result in a Python object
> > PyObject *finalResult;
> >
> > // get arguments from Python
> > char *result = 0;
> > char *in= 0;
> > char *aString = 0;
> > char *bString = 0;
> > MY_NUM *a;
> > MY_NUM *b;
> > int ok = PyArg_ParseTuple(args, "sss", &in, &aString, &bString);
> > if (!ok) return 0;
> >
> > // do work to get a and b
> > // count - returns an int; GetVal - returns a char *
> > a = GetVal(aString, count(aString, ","));
> > b = GetVal(bString, count(bString, ","));
> >
> > // make function call, which returns a char *
> > result = doStuff(in, a, b);
> >
> > // save result in Python string
> > finalResult = PyString_FromString(result);
> >
> > // free memory
> > PyMem_Free(result);
> > PyMem_Free(a);
> > PyMem_Free(b);
> >
> > // return the result as a Python string
> > return finalResult;
> > }
> >
> > ...from python I can call this function 4 times...works fine. WHen I
> > call it for the fifth time python.exe crashes. im thinking some memory
> > problem in the wrapper function perhaps...but I am not sure. The
> > actually C function, doStuff can be called 5, 6,7...N times without a
> > problem
> > so i know its gotta be my wrapper.
> >
> > Any ideas? Thanks!
>
> Well assuming your doStuff is a C function that knows nothing of python.
> it might be the PyMem_Free(result).
> http://docs.python.org/api/memoryInterface.html says the following:
>
> void PyMem_Free(void *p)
> Frees the memory block pointed to by p, which must have been
> returned by a previous call to PyMem_Malloc() or PyMem_Realloc().
> Otherwise, or if PyMem_Free(p) has been called before, undefined
> behavior occurs. If p is NULL, no operation is performed.
>
> But your result wasn't allocated by a PyMem_Malloc, it was returned
> to you by a C function.
>
> --
> Antoon Pardon
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