[Boost-users] TypeError: No registered converter was able to extract a C++ pointer to type char from this Python object of type str

Subject: [Boost-users] TypeError: No registered converter was able to extract a C++ pointer to type char from this Python object of type str
From: Brian Ray (brianhray_at_[hidden])
Date: 2010-08-13 10:25:22

Hello:

I think I am experience a build problem here but not really sure;
nonetheless, below is a simple example that illustrates my problem.

Any idea what I might be doing wrong.  I am using boost_1_43_0 built
with gcc 4.2.1 on i686 running darwin. I am linking to the standard
2.5 python that comes with the distro.

Please note that the PyRun_SimpleString("import sys"); does not error
at all.  The error comes from when the call to import().  I am not
sure if this is  a clue or not but gdb seems not to know what line it
is on. I am guessing it is just confused because of all the inlines. I
suspect this is a linking issues of some sort. However I did check
that they are all linking to the correct location.  Why does it
convert the const char * to a str in the first place. Seems to be
thrashing around a bit.

-- Brian

///  contents of boost_python_issue.cpp
#include <boost/python.hpp>
using namespace boost::python;

int main(int argc, char **argv)
{
 Py_Initialize();
 try {
    PyRun_SimpleString("import sys");
    // This raises exception
    object sys = import("sys");
 } catch (boost::python::error_already_set) {
    PyErr_Print();
 }
 Py_Finalize();
}

// Compiled with 'g++  -I. -I/usr/include -I/usr/local/include
-I../../includes/python2_5_1 -g -L/usr/local/lib
boost_python_issue.cpp   -lboost_system  -lboost_python  -lm
-lpython2.5 -o boost_python_issue'

Output from gdb:

(gdb) break main
Breakpoint 1 at 0x100001319: file boost_python_issue.cpp, line 9.
(gdb) r
Starting program: /Project/zephyr/src/Composer/boost_python_issue
Reading symbols for shared libraries .++++++++..... done

Breakpoint 1, main (argc=1, argv=0x7fff5fbff6d8) at boost_python_issue.cpp:9
9                Py_Initialize();
(gdb) s
11           PyRun_SimpleString("import sys");
(gdb)
13           object sys = import("sys");
(gdb)
boost::python::str::str (this=0x7fff5fbff690, s=0x10000169d "sys") at
str.hpp:150
150         str(const char* s) : base(s) {} // new str
(gdb)
boost::python::detail::str_base::str_base (this=0x7fff5fbff690,
s=0x10000169d "sys") at libs/python/src/str.cpp:39
39                  ))
(gdb)
object [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/object_core.hpp:534
Line number 534 out of range; errors.hpp has 55 lines.
(gdb)
expect_non_null<PyObject> [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/errors.hpp:43
44          if (x == 0)
(gdb)
object [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/object_core.hpp:513
534         : object_base(expect_non_null((PyObject*)p))
(gdb)
object_base [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/object_core.hpp:513
513         : m_ptr(p)
(gdb)
boost::python::detail::str_base::str_base (this=0x7fff5fbff690,
s=<value temporarily unavailable, due to optimizations>) at
libs/python/src/str.cpp:40
40      {}
(gdb)
0x000000010000154d in boost::python::str::str (this=0x7fff5fbff690,
s=0x10000169d "sys") at str.hpp:150
150         str(const char* s) : base(s) {} // new str
(gdb)
boost::python::import (name=@0x7fff5fbff690) at libs/python/src/import.cpp:19
19        char *n = python::extract<char *>(name);
(gdb)
extract [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/extract.hpp:156
156     # else
(gdb)
boost::python::api::object_base::ptr () at
/Users/bray/sources/boost_1_43_0/boost/python/object_core.hpp:542
543         return m_ptr;
(gdb)
extract [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/extract.hpp:216
156         : base(o.ptr())
(gdb)
extract_pointer [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/extract.hpp:216
219               )
(gdb)
boost::python::converter::get_lvalue_from_python (source=0x1005cb1e0,
converters=@0x100409500) at
libs/python/src/converter/from_python.cpp:128
128         void* x = objects::find_instance_impl(source,
converters.target_type);
(gdb)
boost::python::objects::find_instance_impl (inst=0x1005cb1e0,
type={<boost::totally_ordered<boost::python::type_info,boost::python::type_info,boost::detail::empty_base<boost::python::type_info>,boost::detail::false_t>>
= {<boost::totally_ordered1<boost::python::type_info,boost::detail::empty_base<boost::python::type_info>
>> = {<boost::less_than_comparable1<boost::python::type_info,boost::equality_comparable1<boost::python::type_info,
boost::detail::empty_base<boost::python::type_info> > >> =
{<boost::equality_comparable1<boost::python::type_info,boost::detail::empty_base<boost::python::type_info>
>> = {<boost::detail::empty_base<boost::python::type_info>> = {<No
data fields>}, <No data fields>}, <No data fields>}, <No data
fields>}, <No data fields>}, m_base_type = 0x7fff885a066c "c"},
null_shared_ptr_only=false) at libs/python/src/object/class.cpp:485
485           if (Py_TYPE(Py_TYPE(inst)) != &class_metatype_object)
(gdb)
490           for (instance_holder* match = self->objects; match != 0;
match = match->next())
(gdb)
497       }
(gdb)
boost::python::converter::get_lvalue_from_python (source=0x1005cb1e0,
converters=@0x100409500) at
libs/python/src/converter/from_python.cpp:129
129         if (x)
(gdb)
132         lvalue_from_python_chain const* chain = converters.lvalue_chain;
(gdb)
133         for (;chain != 0; chain = chain->next)
(gdb)
135             void* r = chain->convert(source);
(gdb)
boost::python::converter::(anonymous namespace)::convert_to_cstring
(obj=0x1005cb1e0) at
libs/python/src/converter/builtin_converters.cpp:46
46            return PyString_Check(obj) ? PyString_AsString(obj) : 0;
(gdb)
47        }
(gdb)
boost::python::converter::get_lvalue_from_python (source=0x1005cb1e0,
converters=<value temporarily unavailable, due to optimizations>) at
libs/python/src/converter/from_python.cpp:136
136             if (r != 0)
(gdb)
132         lvalue_from_python_chain const* chain = converters.lvalue_chain;
(gdb)
133         for (;chain != 0; chain = chain->next)
(gdb)
140     }
(gdb)
0x00000001001a1128 in extract_pointer [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/extract.hpp:219
219               )
(gdb)
boost::python::import (name=<value temporarily unavailable, due to
optimizations>) at libs/python/src/import.cpp:19
19        char *n = python::extract<char *>(name);
(gdb)
boost::python::extract<char*>::operator char* () at
/Users/bray/sources/boost_1_43_0/boost/python/extract.hpp:138
138             return (*this)();
(gdb)
boost::python::converter::extract_pointer<char*>::operator() () at
extract.hpp:231
232           if (m_result == 0 && m_source != Py_None)
(gdb)
boost::python::converter::extract_pointer<char*>::operator() () at
extract.hpp:233
233               (throw_no_pointer_from_python)(m_source,
registered_pointee<Ptr>::converters);
(gdb)
boost::python::converter::throw_no_pointer_from_python
(source=0x1005cb1e0, converters=@0x100409500) at
libs/python/src/converter/from_python.cpp:256
256         (throw_no_lvalue_from_python)(source, converters, "pointer");
(gdb)
257     }
(gdb)
boost::python::converter::throw_no_pointer_from_python
(source=0x1005cb1e0, converters=@0x100409500) at
libs/python/src/converter/from_python.cpp:256
256         (throw_no_lvalue_from_python)(source, converters, "pointer");
(gdb)
boost::python::converter::(anonymous
namespace)::throw_no_lvalue_from_python (source=0x1005cb1e0,
converters=@0x100409500, ref_type=0x1001a8e55 "pointer") at
libs/python/src/converter/from_python.cpp:201
201       void throw_no_lvalue_from_python(PyObject* source,
registration const& converters, char const* ref_type)
(gdb)
215                   ));
(gdb)
boost::python::type_info::name () at
/Users/bray/sources/boost_1_43_0/boost/python/type_id.hpp:156
156     {
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
libs/python/src/converter/type_id.cpp:116
116           static mangling_map demangler;
(gdb)
121                 , compare_first_cstring());
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::end () at
/usr/include/c++/4.2.1/bits/stl_vector.h:349
349         inline bool
(gdb)
__normal_iterator [inlined] () at /usr/include/c++/4.2.1/bits/stl_iterator.h:654
817         { return __lhs.base() - __rhs.base(); }
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::end () at
/usr/include/c++/4.2.1/bits/stl_vector.h:331
331           { return iterator(this->_M_impl._M_start); }
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
libs/python/src/converter/type_id.cpp:121
121                 , compare_first_cstring());
(gdb)
lower_bound<__gnu_cxx::__normal_iterator<std::pair<const char*, const
char*>*, std::vector<std::pair<const char*, const char*>,
std::allocator<std::pair<const char*, const char*> > > >,
std::pair<const char*, const char*>,
boost::python::<unnamed>::compare_first_cstring> [inlined] () at
/usr/include/c++/4.2.1/bits/stl_algo.h:98
98            return __last - __first;
(gdb)
operator-<std::pair<const char*, const char*>*,
std::vector<std::pair<const char*, const char*>,
std::allocator<std::pair<const char*, const char*> > > > [inlined] ()
at /usr/include/c++/4.2.1/bits/stl_iterator_base_funcs.h:119
119                                  std::__iterator_category(__first));
(gdb)
__distance<__gnu_cxx::__normal_iterator<std::pair<const char*, const
char*>*, std::vector<std::pair<const char*, const char*>,
std::allocator<std::pair<const char*, const char*> > > > > [inlined]
() at /usr/include/c++/4.2.1/bits/stl_iterator_base_funcs.h:2948
Line number 2948 out of range; stl_iterator_base_funcs.h has 182 lines.
(gdb)
distance<__gnu_cxx::__normal_iterator<std::pair<const char*, const
char*>*, std::vector<std::pair<const char*, const char*>,
std::allocator<std::pair<const char*, const char*> > > > > [inlined]
() at /usr/include/c++/4.2.1/bits/stl_iterator.h:116
156           __i += __n;
(gdb)
lower_bound<__gnu_cxx::__normal_iterator<std::pair<const char*, const
char*>*, std::vector<std::pair<const char*, const char*>,
std::allocator<std::pair<const char*, const char*> > > >,
std::pair<const char*, const char*>,
boost::python::<unnamed>::compare_first_cstring> [inlined] () at
/usr/include/c++/4.2.1/bits/stl_algo.h:2952
2952          while (__len > 0)
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
libs/python/src/converter/type_id.cpp:121
121                 , compare_first_cstring());
(gdb)
123           if (p == demangler.end() || strcmp(p->first, mangled))
(gdb)
128                   );
(gdb)
132               if (status == -1)
(gdb)
143                       : keeper.p;
(gdb)
152                   if (cxxabi_cxa_demangle_is_broken()
(gdb)
cxxabi_cxa_demangle_is_broken [inlined] () at
/Users/bray/sources/boost_1_43_0/libs/python/src/converter/type_id.cpp:94
97          if (!was_tested) {
(gdb)
99              free_mem keeper(cxxabi::__cxa_demangle("b", 0, 0, &status));
(gdb)
100             was_tested = true;
(gdb)
101             if (status == -2 || strcmp(keeper.p, "bool") != 0) {
(gdb)
103             }
(gdb)
~free_mem [inlined] () at
/Users/bray/sources/boost_1_43_0/libs/python/src/converter/type_id.cpp:86
87                std::free(p);
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
libs/python/src/converter/type_id.cpp:152
152                   if (cxxabi_cxa_demangle_is_broken()
(gdb)
183                   p = demangler.insert(p, std::make_pair(mangled,
demangled));
(gdb)
331           { return iterator(this->_M_impl._M_start); }
(gdb)
183                   p = demangler.insert(p, std::make_pair(mangled,
demangled));
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::insert () at
/usr/include/c++/4.2.1/bits/vector.tcc:93
95            if (this->_M_impl._M_finish != this->_M_impl._M_end_of_storage
(gdb)
102             _M_insert_aux(__position, __x);
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::_M_insert_aux
(this=0x1001bfd40, __position={_M_current = 0x0}, __x=@0x7fff5fbff5a0)
at vector.tcc:245
245         _M_insert_aux(iterator __position, const _Tp& __x)
(gdb)
247           if (this->_M_impl._M_finish != this->_M_impl._M_end_of_storage)
(gdb)
260               const size_type __old_size = size();
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::size () at
/usr/include/c++/4.2.1/bits/stl_vector.h:400
400           { return size_type(this->_M_impl._M_finish -
this->_M_impl._M_start); }
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::_M_insert_aux
(this=0x1001bfd40, __position={_M_current = 0x0}, __x=@0x7fff5fbff5a0)
at vector.tcc:261
261               if (__old_size == this->max_size())
(gdb)
267               size_type __len = __old_size != 0 ? 2 * __old_size :
1;
(gdb)
88              if (__builtin_expect(__n > this->max_size(), false))
(gdb)
91              return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
(gdb)
275                   __new_finish =
(gdb)
__uninitialized_copy_a<std::pair<const char*, const char*>*,
std::pair<const char*, const char*>*, std::pair<const char*, const
char*> > [inlined] () at
/usr/include/c++/4.2.1/bits/stl_uninitialized.h:114
114                                                _Is_POD());
(gdb)
__uninitialized_copy_aux<std::pair<const char*, const char*>*,
std::pair<const char*, const char*>*> [inlined] () at
stl_uninitialized.h:254
254         { return std::uninitialized_copy(__first, __last, __result); }
(gdb)
uninitialized_copy<std::pair<const char*, const char*>*,
std::pair<const char*, const char*>*> [inlined] () at
stl_uninitialized.h:254
254         { return std::uninitialized_copy(__first, __last, __result); }
(gdb)
__gnu_cxx::new_allocator<std::pair<char const*, char const*>
>::construct () at /usr/include/c++/4.2.1/ext/new_allocator.h:107
107           { ::new(__p) _Tp(__val); }
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::_M_insert_aux
(this=0x1001bfd40, __position={_M_current = 0x0}, __x=@0x7fff5fbff5a0)
at vector.tcc:280
280                   ++__new_finish;
(gdb)
281                   __new_finish =
(gdb)
__uninitialized_copy_a<std::pair<const char*, const char*>*,
std::pair<const char*, const char*>*, std::pair<const char*, const
char*> > [inlined] () at
/usr/include/c++/4.2.1/bits/stl_uninitialized.h:114
114                                                _Is_POD());
(gdb)
__uninitialized_copy_aux<std::pair<const char*, const char*>*,
std::pair<const char*, const char*>*> [inlined] () at
stl_uninitialized.h:254
254         { return std::uninitialized_copy(__first, __last, __result); }
(gdb)
uninitialized_copy<std::pair<const char*, const char*>*,
std::pair<const char*, const char*>*> [inlined] () at
stl_uninitialized.h:254
254         { return std::uninitialized_copy(__first, __last, __result); }
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::_M_insert_aux
(this=0x1001bfd40, __position={_M_current = 0x0}, __x=<value
temporarily unavailable, due to optimizations>) at vector.tcc:293
293               std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
(gdb)
295               _M_deallocate(this->_M_impl._M_start,
(gdb)
std::_Vector_base<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::_M_deallocate
() at /usr/include/c++/4.2.1/bits/stl_vector.h:135
136             if (__p)
(gdb)
std::vector<std::pair<char const*, char const*>,
std::allocator<std::pair<char const*, char const*> > >::_M_insert_aux
(this=0x1001bfd40, __position={_M_current = 0x0}, __x=<value
temporarily unavailable, due to optimizations>) at vector.tcc:298
298               this->_M_impl._M_start = __new_start;
(gdb)
299               this->_M_impl._M_finish = __new_finish;
(gdb)
300               this->_M_impl._M_end_of_storage = __new_start + __len;
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
vector.tcc:103
103           return iterator(this->_M_impl._M_start + __n);
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
libs/python/src/converter/type_id.cpp:183
183                   p = demangler.insert(p, std::make_pair(mangled,
demangled));
(gdb)
185               }
(gdb)
~free_mem [inlined] () at
/Users/bray/sources/boost_1_43_0/libs/python/src/converter/type_id.cpp:86
87                std::free(p);
(gdb)
boost::python::detail::gcc_demangle (mangled=0x7fff885a066c "c") at
libs/python/src/converter/type_id.cpp:189
189       }
(gdb)
boost::python::converter::(anonymous
namespace)::throw_no_lvalue_from_python (source=<value temporarily
unavailable, due to optimizations>, converters=<value temporarily
unavailable, due to optimizations>, ref_type=0x1001a8e55 "pointer") at
libs/python/src/converter/from_python.cpp:215
215                   ));
(gdb)
handle<PyObject> [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/handle.hpp:75
75              : m_p(
(gdb)
boost::python::detail::manage_ptr<_object> (p=0x1005ad6b8) at handle.hpp:55
55        inline T* manage_ptr(T* p, ...)
(gdb)
57            return expect_non_null(p);
(gdb)
expect_non_null<PyObject> [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/errors.hpp:43
44          if (x == 0)
(gdb)
0x000000010018a81d in boost::python::converter::(anonymous
namespace)::throw_no_lvalue_from_python (source=<value temporarily
unavailable, due to optimizations>, converters=<value temporarily
unavailable, due to optimizations>, ref_type=0x1001a8e55 "pointer") at
libs/python/src/converter/from_python.cpp:215
215                   ));
(gdb)
boost::python::converter::(anonymous
namespace)::throw_no_lvalue_from_python (source=<value temporarily
unavailable, due to optimizations>, converters=<value temporarily
unavailable, due to optimizations>, ref_type=0x1001a8e55 "pointer") at
libs/python/src/converter/from_python.cpp:217
217           PyErr_SetObject(PyExc_TypeError, msg.get());
(gdb)
219           throw_error_already_set();
(gdb)
boost::python::throw_error_already_set () at libs/python/src/errors.cpp:61
61          throw error_already_set();
(gdb)
error_already_set [inlined] () at
/Users/bray/sources/boost_1_43_0/boost/python/errors.hpp:19
19        virtual ~error_already_set();
(gdb)
boost::python::throw_error_already_set () at libs/python/src/errors.cpp:61
61          throw error_already_set();
(gdb)
TypeError: No registered converter was able to extract a C++ pointer
to type char from this Python object of type str

Program exited normally.