Mailman 3 October 2010 - Cplusplus-sig

Using boost.python with Makefile (no bjam)
by Philipp Münzel Oct. 6, 2010

Oct. 6, 2010

Hi everyone, thanks to hints on this list I've now got a working build of boost.python. I built the hello world exmaple (using the jam-file) and ran the testsuite with success. Now I want to get used to boost.python by exporting a few functions of a C++ lib I'm working on. This lib uses make as buildtool. Therefore I want to know how to setup a Makefile for boost.python. To start from ground up, I just took the example source code from libs/python/example/tutorial/hello.cpp and tried to compile and link it as a shared library. Unfortunately, there remain undefined symbols, which is why it cannot be loaded as python module. My boost installation is under /usr/local and is built in system layout as static libraries (libboost_x.a). $ cat hello.cpp // Copyright Joel de Guzman 2002-2004. Distributed under the Boost // Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt // or copy at http://www.boost.org/LICENSE_1_0.txt) // Hello World Example from the tutorial // [Joel de Guzman 10/9/2002] #include <boost/python/module.hpp> #include <boost/python/def.hpp> char const* greet() { return "hello, world"; } BOOST_PYTHON_MODULE(hello_ext) { using namespace boost::python; def("greet", greet); } $ g++ -I/usr/local/include -I/usr/include/python -fpic -c -o hello.o hello.cpp $ g++ -shared -Wl,-soname,"libhello.so" -o libhello.so hello.o $ nm -u libhello.so U PyString_Type w _Jv_RegisterClasses U _Py_NoneStruct U _Unwind_Resume@@GCC_3.0 U _ZN5boost6python6detail11init_moduleEPKcPFvvE U _ZN5boost6python6detail12gcc_demangleEPKc U _ZN5boost6python6detail17scope_setattr_docEPKcRKNS0_3api6objectES3_ U _ZN5boost6python7objects15function_objectERKNS1_11py_functionE U _ZN5boost6python7objects21py_function_impl_baseD2Ev U _ZN5boost6python9converter19do_return_to_pythonEPKc U _ZN5boost6python9converter8registry5queryENS0_9type_infoE U _ZNK5boost6python7objects21py_function_impl_base9max_arityEv U _ZNK5boost6python9converter12registration25expected_from_python_typeEv U _ZTIN5boost6python7objects21py_function_impl_baseE U _ZTIPKc@@CXXABI_1.3 U _ZTIc@@CXXABI_1.3 U _ZTVN10__cxxabiv120__si_class_type_infoE@@CXXABI_1.3 U _ZTVN5boost6python7objects21py_function_impl_baseE U _ZdlPv@@GLIBCXX_3.4 U _Znwm@@GLIBCXX_3.4 U __cxa_atexit@@GLIBC_2.2.5 w __cxa_finalize@@GLIBC_2.2.5 U __cxa_guard_abort@@CXXABI_1.3 U __cxa_guard_acquire@@CXXABI_1.3 U __cxa_guard_release@@CXXABI_1.3 w __gmon_start__ U __gxx_personality_v0@@CXXABI_1.3 $ python >>> import libhello Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: ./libhello.so: undefined symbol: _ZNK5boost6python7objects21py_function_impl_base9max_arityEv So what is the big magic of bjam that when bjam links libboost_python.a I get no undefined symbols, but when i do it "by hand" i get these? Regards, Philipp

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How to compile Boost.Python for 32bit on 64bit Linux
by Philipp Münzel Oct. 5, 2010

Oct. 5, 2010

Hi everyone, I'm trying to build a Boost.Python 32bit static library on a 64bit Linux (Suse 11.3). Of course, I have the respective python-devel and python32 packages for my platform installed. I build my minimal work environment of boost-thread, -system and -python with this command: sudo ./bjam install -q --layout=system --with-system --with-thread --with-python toolset=gcc variant=release link=static threading=multi runtime-link=static address-model=32 As long as I don't include the --with-python option, I get the expected result: 32bit static libraries. But with --with-python, I get the following error: gcc.compile.c++ bin.v2/libs/python/build/gcc-4.5/release/address-model-32/link-static/runtime-link-static/threading-multi/numeric.o In file included from /usr/include/python2.6/Python.h:58:0, from ./boost/python/detail/wrap_python.hpp:142, from ./boost/python/detail/prefix.hpp:13, from ./boost/python/numeric.hpp:8, from libs/python/src/numeric.cpp:6: /usr/include/python2.6/pyport.h:685:2: error: #error "LONG_BIT definition appears wrong for platform (bad gcc/glibc config?)." "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -pthread -m32 -DBOOST_ALL_NO_LIB=1 -DBOOST_PYTHON_SOURCE -DBOOST_PYTHON_STATIC_LIB -DNDEBUG -I"." -I"/usr/include/python2.6" -c -o "bin.v2/libs/python/build/gcc-4.5/release/address-model-32/link-static/runtime-link-static/threading-multi/numeric.o" "libs/python/src/numeric.cpp" ...failed gcc.compile.c++ bin.v2/libs/python/build/gcc-4.5/release/address-model-32/link-static/runtime-link-static/threading-multi/numeric.o... ...failed updating 1 target... Apparently, my python headers in /usr/include/python2.6 make the assumption that on a 64bit platform one wants to build always 64bit libraries. How can I compile boost.python for 32bit without having to edit the respective header file and hard-coding the word size, which would render it unusable for a native build? Any help is appreciated. Regards, Philipp

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[python] base::get_override() exception set
by Trigve Siver Oct. 1, 2010

Oct. 1, 2010

Hi, when calling get_override() method while trying to find python overload and overload is not found exception in python is set. This is because PyObject_GetAttrString() is used for retrieving the attribute. If attribute is not found, PyObject_GetAttrString() set the exception. This is using python 3.1. I've created ticket https://svn.boost.org/trac/boost/ticket/4701 with patch. Could anyone look at this? Thanks Trigve

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