[Swig-devel] [PATCH] Passing None to the constructor of a class when %implicitconv is defined.

[Bo P. <be...@gm...>]

Dear SWIG developers,

I am writing to see if you could kindly have a look at the following
patch, which, instead of treating None always as NULL, passes NULL to
the constructor of a class when %implicitconv is defined. The
motivation of this patch is that I would like to make None a valid
input of a customized type but the way SWIG handles None makes it
impossible to pass None to the constructor of the class. I have
attached a simple example that demonstrates the current behavior. The
patch seems to work but I do not know any side effect of it.

Thank you very much.
Bo


Index: Lib/python/pyrun.swg
===================================================================
--- Lib/python/pyrun.swg        (revision 11674)
+++ Lib/python/pyrun.swg        (working copy)
@@ -1065,7 +1065,7 @@
 SWIGRUNTIME int
 SWIG_Python_ConvertPtrAndOwn(PyObject *obj, void **ptr,
swig_type_info *ty, int flags, int *own) {
   if (!obj) return SWIG_ERROR;
-  if (obj == Py_None) {
+  if (obj == Py_None && !(flags & SWIG_POINTER_IMPLICIT_CONV)) {
     if (ptr) *ptr = 0;
     return SWIG_OK;
   } else {


================== test.h ========
class Foo {
public:
Foo(int * i) : num(i == NULL ? 0 : 1) {}
private:
int num;
};

void func(Foo f)
{
}
============= test.i =================
%module test

%{
#include "test.h"
%}

%implicitconv Foo;

%include "test.h"

=============== command =============
% swig -c++ -python -shadow test.i
% g++ test_wrap.cxx -shared -o _test.so -fPIC -I/usr/include/python2.4

I get a module test with type Foo that cannot be implicitly converted:

>>> from test import *
>>> func(Foo(None))
>>> func(None)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
ValueError: invalid null reference in method 'func', argument 1 of type
'Foo'

For the last command, I would expect that None is passed to Foo(int *).