[C++-sig] Re: Parameter translation python, C++
David Abrahams
dave at boost-consulting.com
Wed Aug 13 17:57:20 CEST 2003
Stefan Fleiter <sf.lists at web.de> writes:
> Hi,
>
>>>when I call a boost::python method from python
>>>with a parameter of type float and there is only
>>>a C++ Method with a parameter of type double
>>>I get an "unidentifiable C++ exception".
>
>>>C++-Code:
>>>--------------------------------------------------------
>>>void pybind(db::ExtCursor& cur, int column, float value)
>
> Sorry, this is a double, I had two shells open and copied this from
> the working version.
>
>> I can't believe your compiler lets you get away with this.
> No, g++ 3.2.3 would not do that. :-)
>
>>> py::class_< db::ExtCursor, boost::noncopyable >("ExtCursor",
>>> py::init< db::Connection& >())
>>> .def("bind", bind4, "bind value to query")
>>>}
>>>
>>>Python-Code:
>>>--------------------------------------------------------
>>>self._cCursor.bind(0, 2.3) // _cCursor is db::ExtCursor
>
>> Anyway, the exception is either:
>> 1. Actually a crash (most likely in your code), if you're running on
>> windows. Try #including libs/python/test/module_tail.cpp in your
>> module
> I do run Linux.
> I get the exception even if pybind is defined empty ( {} ).
>
>
>> 2. A regular C++ exception thrown by your code for which you've not
>> installed a translator.
> See above, an empty method can't throw an exception.
>
> And last but not least:
> If I change "double" to "float" everything is ok.
>
Honestly, I don't see how this could have anything to do with
Boost.Python. If it doesn't fail on the following code, I think it
has to be in your code. If it does, I think it has to be a compiler
bug.
#include <boost/python.hpp>
namespace db
{
struct ExtCursor
{
ExtCursor(int) {}
};
}
void pybind(db::ExtCursor& cur, int column, double value)
{
}
namespace py = boost::python;
BOOST_PYTHON_MODULE(foo_ext)
{
void (*bind4)(db::ExtCursor&, int, double) = &pybind;
py::class_< db::ExtCursor, boost::noncopyable >(
"ExtCursor", py::init< int >())
.def("bind", bind4, "bind value to query")
;
}
----------
from foo_ext import *
print ExtCursor(3).bind(0, 2.3)
--
Dave Abrahams
Boost Consulting
www.boost-consulting.com
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