[C++-sig] problem with python::dict[]

[David Abrahams]

harold fellermann <harold at imb-jena.de> writes:

> Hello,
>
> I got your address from
> http://mail.python.org/pipermail/c++-sig/2002-June/001311.html -- so I
> don't know whether you are the right person to ask.

"We" are the right people to ask.  You sent it to the appropriate
place: c++-sig at python.org.

> I think I have found an error in the boost.python's dict-interface.
>
> My following code-snippet runs into segmantation fault:
>
> #include <stdlib.h>
> #include <boost/python/dict.hpp>
>
> using namespace boost::python;
>
> int main()
> {
>    dict x[750];
>
>    return 0;
> }


Do you really mean to construct an array of 750 dicts?  I think if
you're going to do that from a program (as opposed to an extension
module) you'll need to call some things like PyInitialize() first.
See libs/python/test/embedding.cpp for an example.

> The problem seems to concern the garbage collector from the
> Python/C-API, as
> my debugger tells me, the program crashes in _PyObject_GC_New():
>
>
> (gdb) run
> Starting program: /home/tsb/harold/c_network/pytest
> [New Thread 1024 (LWP 25905)]
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 1024 (LWP 25905)]
> 0x0809a909 in PyErr_Occurred ()
> (gdb) bt
> #0  0x0809a909 in PyErr_Occurred ()
> #1  0x080addca in _PyObject_GC_New ()
> #2  0x08064edc in PyDict_New ()
> #3  0x4003b1f4 in boost::python::detail::dict_base::dict_base() ()
>     from /usr/local/lib/libboost_python.so.1.29.0
> #4  0x080c6c6c in main () at pytest.c:9
> #5  0x401744a2 in __libc_start_main () from /lib/libc.so.6
>
>
> I tried this with a couple of python-objects and all containers (dict,
> list, ...)
> crashed in exactly the same way. Interestingly the program behaves
> normal when
> I reduce the number of objects within my array to approx. 700.

Very interesting, but inconclusive.

> My configuration looks as follows:
> - python 2.2.1 (#1, Sep 10 2002, 17:49:17)
> - gcc 3.2
> - boost version 1.29.0
>
> Do you have any idea what is going on here? Is this a known bug,
> maybe even a nowadays fixed one? Or is it only a question of
> configuration?  Any help will be appreciated!

It's hard to imagine any bug in Boost.PYthon that would depend on the
size of the array being small; maybe one in the compiler or in Python
could do that.

This works on my system:

#include <stdlib.h>
#include <boost/python/dict.hpp>

using namespace boost::python;

void test()
{
    // Initialize the interpreter
    Py_Initialize();
    dict d[750];
}

int main()
{
    if (handle_exception(test))
    {
        if (PyErr_Occurred())
            PyErr_Print();
        return 1;
    }
    return 0;
}

HTH,
-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com