I am testing a wrapper on Windows 64 and it seems to result in an null pointer access error ONLY when I insert a print statement in the C code.  I have tested the wrapper with Python 2.6 and Python 2.7a4.  In addition, I have compiled Python 2.6.5 source code and ONLY the release version results in an error.  I think the issue is with memcpy(obj->b_ptr, *pArgs, dict->size) (callbacks.c).  pArgs seem to be  corrupted.  However, I am only looking at the code for the first time and I might be off base.

The following is Python and C code to reproduce the bug.  To resolve, please comment printf statement in jfunc (C function).

Python Code:
from ctypes import *
def fcn(m,n,x,f):
    print "IN Python function fcn ................"
    print f[0]
    
m=3
n=1
pydlltest=cdll.pydlltest
pydlltest.jfunc.restype = POINTER(c_double)
evalstring = 'pydlltest.jfunc('
TMP_FCN=CFUNCTYPE(None,c_int,c_int,POINTER(c_double),POINTER(c_double))
tmp_fcn=TMP_FCN(fcn)
state=[TMP_FCN,tmp_fcn]
evalstring += 'tmp_fcn'
evalstring +=','
evalstring +='c_int(m)'
evalstring +=','
evalstring +='c_int(n)'
evalstring += ')'
print "evalstring=",evalstring
result = eval(evalstring)

C code:
#include <stdio.h>
__declspec(dllexport) double *jfunc(void (*fcn) (int,int,double [],double[]),int m,int n);

double *jfunc(void (*fcn) (int,int,double [],double []),int m,int n)
{
	double *fvec=NULL;
	double *xguess = NULL;
	int i = 0;
	int j = 0;
	/* comment the line below to fix the resulting null pointer access error */
	printf("In j func .................\n");
	fvec = (double *) malloc (m * sizeof (double));
	xguess = (double *) malloc (n * sizeof (double));
	for (i = 0; i < n; i++){
	   xguess[i] = 0.123;
	}
	(*fcn) (m, n, xguess, fvec);
	return fvec;
}