November 2001 - Boost-users - lists.preview.boost.org

"referenced symbol not found" when loading modules
by dlrubin＠yahoo.com 25 Nov '01

25 Nov '01

I'm getting a "refernced symbol not found" error when loading modules compiled with Boost. I tried using boost using this example code: #include <stdio.h> #include <string> #include <boost/python/class_builder.hpp> namespace { std::string greet() { return "hello, world"; } int square(int number) { return number * number; } } namespace python = boost::python; BOOST_PYTHON_MODULE_INIT(example) { try { // Create an object representing this extension module. python::module_builder this_module("example"); // Add regular functions to the module. this_module.def(greet, "greet"); } catch(...) { python::handle_exception(); // Deal with the exception for Python } } and when I try importing into python, here's the error I get: Python 2.1.1 (#5, Nov 22 2001, 14:04:45) [GCC 2.95.2 19991024 (release)] on sunos5 Type "copyright", "credits" or "license" for more information. >>> import example Traceback (most recent call last): File "<stdin>", line 1, in ? ImportError: ld.so.1: python: fatal: relocation error: file ./example.so: symbol handle_exception__Q25boost6pythonv: referenced symbol not found Any suggestions? thanks, Daniel

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Introducing Me
by Paul Grenyer 24 Nov '01

24 Nov '01

Dear All I don't know if this is the appropriate thing to do here (I'm sure the moderator will filter me out if it isn't), but I failed to introduce myself on other lists and with hindsight I think it would have been better if I had. I've been programming in C++ for about 18 months, since I left university and started working. I was introduced to the C++ standard library and boost libraries a few months ago by a member of the ACCU. I have just started a new job writing distributed software using the C++ standard library and the ATL and I'm making as much use of boost as possible. Previous to that I was writing windows software to control dot markers and laser markers using the MFC. So, I am very new to boost and am not expecting to be able to contribute much for a while and I'll no doubt need the odd nudge in the right direct. Thanks Paul Paul Grenyer pjgrenyer(a)iee.org

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Re: [boost] how to get a *real* copy of a boost-python object that supports virtual function
by Phil Austin 24 Nov '01

24 Nov '01

(I'm posting to both boost and boost-users, but I'm assuming we're supposed to move this kind of discussion to Boost-Users(a)yahoogroups.com?) dkottowk(a)yahoo.com writes: [snip] > my question is, how do i get a copy of PyGenome_Callback, > which also is a copy of the python-side of the object ? I'd also be interested in a pointer to an elegant way to do this, as well as an example of a from_python function that converts PyObject* to PyGenome_Callback. Brute force does work for me -- i.e. if you need the derived class and can't construct the object in Python code, you can call the derived constructor from the C++ side like this: PyObject* theMod=PyImport_ImportModule("mymodule"); PyObject* theDict=PyModule_GetDict(theMod); py::ref theRef(theDict); py::dictionary modDict(theRef); py::ref constructor=bDict.get_item(py::string("theObject").reference()); PyObject* theInstance=PyObject_CallObject(constructor.get(),0); This was ugly enough so that I added a python wrapper around my extension to construct the derived objects I needed in Python and pass them back to C++. Phil

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boost tokenizer
by pjgrenyer＠iee.org 23 Nov '01

23 Nov '01

Dear All I'm using the boost tokenizer to tokenise lines similar to this one: first_initial |23|1| This gives me: first initial 23 1 but what I actually want is: first_initial 23 1 Does anyone know how to get it to ignore the underscore? Thanks Paul

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passing data to a thread
by d33pmind＠yahoo.fr 23 Nov '01

23 Nov '01

How can I pass data to a thread ? Why does the boost::thread's constructor takes a boost::function0<void> as parameter, instead of a boost::function1<void> which would have allowed to pass it a pointer to a thread safe structure ? Julien.

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core dump when invoking jam
by d33pmind＠yahoo.fr 23 Nov '01

23 Nov '01

On a Linux Mandrake 8.1 (i586), I succesfully built jam, but when I invoke it I got no output except a core dump. Has anyone encountered the same problem ? I compiled it with gcc 3.0.1, and modified gcc-tools.jam to use gcc- 3.0.1 and g++-3.0.1 instead of gcc and g++ (which are 2.96). Thanks. Julien.

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What's safe_bool?
by mr_lilirong＠yahoo.com 23 Nov '01

23 Nov '01

Hi, The following code is excerpted from Boost.Function. I just don't unstanding it. Why use "safe_bool"? What's the advantage? Can any one explain it to me? Thanks. // code from <boost/function/function_base.hpp> // ===> private: struct dummy { void nonnull() {}; }; typedef void (dummy::*safe_bool)(); public: operator safe_bool () const { return (this->empty())? 0 : &dummy::nonnull; } safe_bool operator!() const { return (this->empty())? &dummy::nonnull : 0; } // code from <boost/function/function_base.hpp> // <===

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aCC compilator
by lokys1976＠yahoo.com 22 Nov '01

22 Nov '01

Is it possible using aCC A.03.27 to use boost libraries? When I try to compile using boost examples, it dosn't understand "using namespece std" and so on, when I try to use aCC -AA than it can not find some libraries. Any suggestions how must I use aCC with boost libraries is welcomed very much thank you Paulius

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Threads on MSVC 6.0
by brian_todoroff＠yahoo.com 22 Nov '01

22 Nov '01

I've been trying for a few hours now to get the threads lib examples to compile. I built the libraries with jam and all but python built correctly. When I create a new Win32 console application and copy the code ( See end of message from the thread class example and attempt to compile I get: ===================Start Error --------------------Configuration: threadtest - Win32 Debug----------- --------- Compiling... threadtest.cpp c:\projects\boost\threadtest\threadtest.cpp(27) : error C2228: left of '.join' must have class/struct/union type Error executing cl.exe. Creating browse info file... threadtest.exe - 1 error(s), 0 warning(s) ===================End Error Can't figure out what I'm doing wrong. Thanks for any help. Brian Todoroff ========================Start Code (to end) #include <boost/thread/xtime.hpp> #include <boost/thread/thread.hpp> #include <iostream> struct thread_alarm { thread_alarm(int secs) : m_secs(secs) { } void operator()() { boost::xtime xt; boost::xtime_get(&xt, boost::TIME_UTC); xt.sec += m_secs; boost::thread::sleep(xt); std::cout << "alarm sounded..." << std::endl; } int m_secs; }; int main(int argc, char* argv[]) { int secs = 5; std::cout << "setting alarm for 5 seconds..." << std::endl; boost::thread thrd(thread_alarm(secs)); thrd.join(); // Line 27 - Error here return 0; }

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breadth_first_searchable graph, without invalidable vertex descriptors
by cristipp＠ics.uci.edu 21 Nov '01

21 Nov '01

Hello, I am trying to use the BCG as backbone for a ControlFlowGraph in a compiler project. It seems that I cannot use BCG for this task because of the follow contradicting (from BCG point of view) requirements: 1. I want to be able to breadth_first_search through my graph. 2. I want to be able to keep descriptors to vertices 'for ever' so I can refer a specific vertex at any given time (for removal or whatever other reasons). To implement requirement 1 my adjacency_list should have its VertexList of type vecS. To implement requirement 2 my adjacency_list should have its VertexList of type listS. Unfortunately those are mutualy exclusive and it seems that BCG is unsuited for the job. But I can't really think of a decent generic graph library unable to support those requirements. After all, it's all about being able to use basic graph traversals on randomly mutating graphs. STL has the list which has those nice properties, why a graph library should be different?! Perhaps I am missing something and I am asking for help: how should I declare my graph and how can I do a bfs on it? Thanks in advance, Cristi

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