Mailman 3 October 2005 - Cplusplus-sig

Re: [C++-sig] Nasty Heap Error in MSVC 7.1 With Boost and PythonUsing Derived Classes
by mjkeyes＠sbcglobal.net Oct. 18, 2005

Oct. 18, 2005

When I use boost::python::import, I'm getting an unresolved external symbol linking error. Any advice? "David Abrahams" <dave(a)boost-consulting.com> wrote in message news:<ur7aqdcmi.fsf(a)boost-consulting.com>... > "Matt" <mjkeyes(a)sbcglobal.net> writes: > > > Hey all, > > > > i'm trying to create an application that both embeds and extends > > python through boost. i've got a rough framework up and running, > > but now that i'm finally to the python part i'm having troubles. > > Please know that i'm a noob to boost and to boost.python, so if you > > see any obvious noob idiocies in my code please point them out > > (we've all got to start learning somewhere :)). > > You should never be doing any Py_XINCREF or Py_XDECREF stuff when > using Boost.Python. Also, you're using an outdated approach to > supporting virtual functions. > > I suggest you follow the example of > http://www.boost-consulting.com/boost/libs/python/test/exec.cpp > > You'll need the latest Boost CVS state in order to use all the idioms > therein, though. > > -- > Dave Abrahams > Boost Consulting > www.boost-consulting.com

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Re: [C++-sig] Memory Leaks In VS.NET 2003 With BOOST_PYTHON_MODULE
by mjkeyes＠sbcglobal.net Oct. 14, 2005

Oct. 14, 2005

*********My apologies... The whitespace in my code was stripped (which makes the Python difficult to read) Here is the message again: Okay, I solved the second problem. Turns out it's something I wouldn't expect. Here's the situation - I have a C++ extended class to use in Python called AccountMgr. When I define a Python class, I do something like this: >>> from MyModule import BaseClass #another extended class from C++ >>> from MyModule import AccountMgr >>> class MyClass(BaseClass): >>> def UseAccountMgr(self): >>> self.acctMgr.DoSomething() >>> acctMgr = AccountMgr() Whenever this module is imported from another, it constructs the acctMgr object (even if I haven't instanced MyClass yet). However, this destructor is never called (I'm guessing because Py_Finalize isn't implemented?). Two followup questions: 1. How should I handle the construction of the acctMgr (or any other extended member variable in a Python class)? I tried supplying an __init__(self) function, but I get some interpreter errors about converting the C++ class to Python. Consequently, for now, I do something like this: >>> class MyClass(BaseClass): >>> def UseAccountMgr(self): >>> if self.acctMgr == None: >>> self.acctMgr = AccountMgr() >>> self.acctMgr.DoSomething() >>> acctMgr = None Can I declare the member variable as self.acctMgr = AccountMgr()? I haven't tried it. 2. Please offer any comments on the Python code above. I'm not green when it comes to C++, but I've only been using Python for about a week, so a little code review here would be helpful. Thanks again! <mjkeyes(a)sbcglobal.net> wrote in message news:<000001c5d078$aee62b20$210110ac@CROW>... > Okay, I solved the second problem. Turns out it's something I > wouldn't expect. > > Here's the situation - I have a C++ extended class to use in Python > called AccountMgr. When I define a Python class, I do something like > this: > > from MyModule import BaseClass #another extended class from C++ from > MyModule import AccountMgr > > class MyClass(BaseClass): > def UseAccountMgr(self): > self.acctMgr.DoSomething() > > acctMgr = AccountMgr() > > Whenever this module is imported from another, it constructs the > acctMgr object (even if I haven't instanced MyClass yet). However, > this destructor is never called (I'm guessing because Py_Finalize > isn't implemented?). > > Two followup questions: > 1. How should I handle the construction of the acctMgr (or any other > extended member variable in a Python class)? I tried supplying an > __init__(self) function, but I get some interpreter errors about > converting the C++ class to Python. Consequently, for now, I do > something like this: > > class MyClass(BaseClass): > def UseAccountMgr(self): > if self.acctMgr == None: > self.acctMgr = AccountMgr() > self.acctMgr.DoSomething() > > acctMgr = None > > Can I declare the member variable as self.acctMgr = AccountMgr()? I > haven't tried it. > > 2. Please offer any comments on the Python code above. I'm not green > when it comes to C++, but I've only been using Python for about a > week, so a little code review here would be helpful. > > Thanks again! > > > "Matthew B. Keyes" <Keyes(a)simcrest.com> wrote in message > news:<6A26270516DF054BBB3B87AE01C831EC2CCBD0(a)SERVER01.simcrest.int>... > > Sorry guys, it was late when I posted this, so the typo: > > > > return object(new CreateClassA()); > > > > Meant to be: > > > > return object(new A()); > > > > I was under the impression that the object class functioned as a > > reference counting auto_ptr of sorts... That solves that one for me. > > > > I'll post more later on the string issue 'cause I'm out of time > > right > > now. Thanks for the help! > > > > "Ralf W. Grosse-Kunstleve" <rwgk(a)yahoo.com> wrote in message > > news:<20051013155914.43599.qmail(a)web31505.mail.mud.yahoo.com>... > > > --- mjkeyes(a)sbcglobal.net wrote: > > > > > > > Hey again, I'm back. > > > > > > Hi Arnold! :) > > > > > > > Here is some pseudo-code of what I'm doing: > > > > > > Could you please turn this into a self-contained reproducer? > > > Please > > explain > > > exactly how you compile and link. Note that you have to be very > > careful to not > > > mix debug and release builds under Windows. > > > > > > > class A > > > > { > > > > public: > > > > void SetString(const std::string &sVal) > > > > { > > > > m_sString = sVal; <--- Memory leak > > > > > > I am doing things like this all the time and I am sure it doesn't > > > leak > > for me. > > > > > > > } > > > > > > > > void DoStuff() > > > > { > > > > SetString(msc_sString); > > > > } > > > > protected: > > > > static const std::string msc_sString; > > > > } > > > > > > Probably a side issue: do you really want "static" here? > > > > > > > > > > > class B > > > > { > > > > public: > > > > object CreateClassA() > > > > { > > > > return object(new CreateClassA()); <---- memory leak > > > > > > What is this? Does this even compile? > > > In any event, of course you get a memory leak if you use new like > > that. > > > Ideally, you don't have any "unencapsulated" new in your code. > > > Always > > use > > > boost::shared_ptr<T>(new T) or std::auto_ptr<>(new T) or any other > > smart > > > pointer. > > > > > > > Any suggestions? I'm not getting any errors from the > > > > interpreter. > > > > > > We need a complete reproducer. > > > > > > Cheers, > > > Ralf > > > > > > > > > > > > > > > __________________________________ > > > Yahoo! Music Unlimited > > > Access over 1 million songs. Try it free. > > > http://music.yahoo.com/unlimited/

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Wrapping a class with private operator&()
by Matthias Baas Oct. 14, 2005

Oct. 14, 2005

Hi, I'm having problems wrapping a C++ class that has a private reference operator (operator&()). Here is a minimal example that shows the problem: #include <boost/python.hpp> using namespace boost::python; class Spam { public: Spam() {} private: Spam* operator&() {return this;} }; BOOST_PYTHON_MODULE(mod) { class_<Spam, boost::noncopyable>("Spam", init<>()); } When I compile this code (either using gcc 3.3.4 on Linux or MSVC 7.1 on WinXP, both with Python 2.4 and boost-1.33.0) I get an error like that attached at the end of this mail. I suppose the relevant part of the message is this: /client/include/boost/python/detail/def_helper.hpp:79: instantiated from here mod.cpp:13: error: `Spam* Spam::operator&()' is private I can compile the code if I specify the class with no_init, but then the wrapper would be useless as it must be possible to create instances of the class. It would be acceptable to have a factory function that actually creates the instances but when I tried that it also didn't compile. So does anybody know how to wrap a class like the above? - Matthias - Error message from gcc: gcc -pthread -fno-strict-aliasing -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -fPIC -I/client/include -I/sw/i386_linux-2.0_glibc2/Python-2.4.1/include/python2.4 -c mod.cpp -o build/temp.linux-i686-2.4/mod.o mod.cpp: In constructor ` boost::python::objects::value_holder<Value>::value_holder(PyObject*) [with Value = Spam]': /client/include/boost/python/object/make_holder.hpp:83: instantiated from `static void boost::python::objects::make_holder<0>::apply<Holder, ArgList>::execute(PyObject*) [with Holder = boost::python::objects::value_holder<Spam>, ArgList = boost::mpl::vector0<mpl_::na>]' /client/include/boost/python/detail/make_keyword_range_fn.hpp:60: instantiated from `boost::python::api::object boost::python::detail::make_keyword_range_constructor(const CallPolicies&, const boost::python::detail::keyword_range&, Holder*, ArgList*, Arity*) [with ArgList = boost::mpl::vector0<mpl_::na>, Arity = boost::mpl::size<boost::mpl::vector0<mpl_::na> >, Holder = boost::python::objects::value_holder<Spam>, CallPolicies = boost::python::default_call_policies]' /client/include/boost/python/init.hpp:330: instantiated from `void boost::python::detail::def_init_aux(ClassT&, const Signature&, NArgs, const CallPoliciesT&, const char*, const boost::python::detail::keyword_range&) [with ClassT = boost::python::class_<Spam, boost::noncopyable, boost::python::detail::not_specified, boost::python::detail::not_specified>, CallPoliciesT = boost::python::default_call_policies, Signature = boost::mpl::vector0<mpl_::na>, NArgs = boost::mpl::size<boost::mpl::vector0<mpl_::na> >]' /client/include/boost/python/init.hpp:399: instantiated from `static void boost::python::detail::define_class_init_helper<0>::apply(ClassT&, const CallPoliciesT&, const Signature&, NArgs, const char*, const boost::python::detail::keyword_range&) [with ClassT = boost::python::class_<Spam, boost::noncopyable, boost::python::detail::not_specified, boost::python::detail::not_specified>, CallPoliciesT = boost::python::default_call_policies, Signature = boost::mpl::vector0<mpl_::na>, NArgs = boost::mpl::size<boost::mpl::vector0<mpl_::na> >]' /client/include/boost/python/init.hpp:171: instantiated from `void boost::python::init_base<DerivedT>::visit(classT&) const [with classT = boost::python::class_<Spam, boost::noncopyable, boost::python::detail::not_specified, boost::python::detail::not_specified>, DerivedT = boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_>]' /client/include/boost/python/def_visitor.hpp:31: instantiated from `static void boost::python::def_visitor_access::visit(const V&, classT&) [with V = boost::python::def_visitor<boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_> >, classT = boost::python::class_<Spam, boost::noncopyable, boost::python::detail::not_specified, boost::python::detail::not_specified>]' /client/include/boost/python/def_visitor.hpp:67: instantiated from `void boost::python::def_visitor<DerivedVisitor>::visit(classT&) const [with classT = boost::python::class_<Spam, boost::noncopyable, boost::python::detail::not_specified, boost::python::detail::not_specified>, DerivedVisitor = boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_>]' /client/include/boost/python/class.hpp:225: instantiated from `boost::python::class_<T, X1, X2, X3>& boost::python::class_<T, X1, X2, X3>::def(const boost::python::def_visitor<Derived>&) [with Derived = boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_>, W = Spam, X1 = boost::noncopyable, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' /client/include/boost/python/class.hpp:501: instantiated from `void boost::python::class_<T, X1, X2, X3>::initialize(const DefVisitor&) [with DefVisitor = boost::python::init_base<boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_> >, W = Spam, X1 = boost::noncopyable, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' /client/include/boost/python/class.hpp:208: instantiated from `boost::python::class_<T, X1, X2, X3>::class_(const char*, const boost::python::init_base<DerivedT>&) [with DerivedT = boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_>, W = Spam, X1 = boost::noncopyable, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' mod.cpp:19: instantiated from here mod.cpp:13: error: `Spam* Spam::operator&()' is private /client/include/boost/python/object/value_holder.hpp:134: error: within this context mod.cpp: In member function `void* boost::python::objects::value_holder<Value>::holds(boost::python::type_info, bool) [with Value = Spam]': /client/include/boost/python/detail/def_helper.hpp:79: instantiated from here mod.cpp:13: error: `Spam* Spam::operator&()' is private /client/include/boost/python/object/value_holder.hpp:89: error: within this context mod.cpp:13: error: `Spam* Spam::operator&()' is private /client/include/boost/python/object/value_holder.hpp:89: error: within this context /client/include/boost/python/detail/def_helper.hpp:79: instantiated from here mod.cpp:13: error: `Spam* Spam::operator&()' is private /client/include/boost/python/object/value_holder.hpp:93: error: within this context mod.cpp:13: error: `Spam* Spam::operator&()' is private /client/include/boost/python/object/value_holder.hpp:93: error: within this context

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[newbie] Question on thread-safe and embedding/extending with boost::python
by Liang Xu Oct. 14, 2005

Oct. 14, 2005

Hi all -- I'm working on an application that is embedding and extending with boost:python for extendability. I is dividing my requirments to the part of features and the part of business rules. The feature is what can i do and the business rule is when do i. The features are stable and the business rules are volatile. I is plan to implement the feature as a C++ method of domain object and the business rule in python script. The domain object's state is saved in C++ code. When The C++ code has received a event, it pass the event and the c++ object as context to python script. The script judge the state of the C++ object then call the C++ method. I have spend two weeks in the research and i have writed a simple application to validate it. But i'm newbie in python and boost.python. I have some questions : 1. Is the solution a good idea? I select the mixed solution because i haven't the experience in python and i really need the extendability. 2. Is it working in multithread application. From "Python/C API Reference Manual -- 8.1 Thread State and the Global Interpreter Lock", i read "The Python interpreter is not fully thread safe. In order to support multi-threaded Python programs, there's a global lock that must be held by the current thread before it can safely access Python objects. Without the lock, even the simplest operations could cause problems in a multi-threaded program: for example, when two threads simultaneously increment the reference count of the same object, the reference count could end up being incremented only once instead of twice. ". But in my application the python object is stateic and readonly after initial, and i just call method that is thread-safe in C++. Can i call the python method in multithread without lock? Or i can use an interpreter on each thread? Attachments are my test application code. -- Liang Xu

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Re: [C++-sig] Memory Leaks In VS.NET 2003 With BOOST_PYTHON_MODULE
by mjkeyes＠sbcglobal.net Oct. 14, 2005

Oct. 14, 2005

Okay, I solved the second problem. Turns out it's something I wouldn't expect. Here's the situation - I have a C++ extended class to use in Python called AccountMgr. When I define a Python class, I do something like this: from MyModule import BaseClass #another extended class from C++ from MyModule import AccountMgr class MyClass(BaseClass): def UseAccountMgr(self): self.acctMgr.DoSomething() acctMgr = AccountMgr() Whenever this module is imported from another, it constructs the acctMgr object (even if I haven't instanced MyClass yet). However, this destructor is never called (I'm guessing because Py_Finalize isn't implemented?). Two followup questions: 1. How should I handle the construction of the acctMgr (or any other extended member variable in a Python class)? I tried supplying an __init__(self) function, but I get some interpreter errors about converting the C++ class to Python. Consequently, for now, I do something like this: class MyClass(BaseClass): def UseAccountMgr(self): if self.acctMgr == None: self.acctMgr = AccountMgr() self.acctMgr.DoSomething() acctMgr = None Can I declare the member variable as self.acctMgr = AccountMgr()? I haven't tried it. 2. Please offer any comments on the Python code above. I'm not green when it comes to C++, but I've only been using Python for about a week, so a little code review here would be helpful. Thanks again! "Matthew B. Keyes" <Keyes(a)simcrest.com> wrote in message news:<6A26270516DF054BBB3B87AE01C831EC2CCBD0(a)SERVER01.simcrest.int>... > Sorry guys, it was late when I posted this, so the typo: > > return object(new CreateClassA()); > > Meant to be: > > return object(new A()); > > I was under the impression that the object class functioned as a > reference counting auto_ptr of sorts... That solves that one for me. > > I'll post more later on the string issue 'cause I'm out of time right > now. Thanks for the help! > > "Ralf W. Grosse-Kunstleve" <rwgk(a)yahoo.com> wrote in message > news:<20051013155914.43599.qmail(a)web31505.mail.mud.yahoo.com>... > > --- mjkeyes(a)sbcglobal.net wrote: > > > > > Hey again, I'm back. > > > > Hi Arnold! :) > > > > > Here is some pseudo-code of what I'm doing: > > > > Could you please turn this into a self-contained reproducer? Please > explain > > exactly how you compile and link. Note that you have to be very > careful to not > > mix debug and release builds under Windows. > > > > > class A > > > { > > > public: > > > void SetString(const std::string &sVal) > > > { > > > m_sString = sVal; <--- Memory leak > > > > I am doing things like this all the time and I am sure it doesn't > > leak > for me. > > > > > } > > > > > > void DoStuff() > > > { > > > SetString(msc_sString); > > > } > > > protected: > > > static const std::string msc_sString; > > > } > > > > Probably a side issue: do you really want "static" here? > > > > > > > > class B > > > { > > > public: > > > object CreateClassA() > > > { > > > return object(new CreateClassA()); <---- memory leak > > > > What is this? Does this even compile? > > In any event, of course you get a memory leak if you use new like > that. > > Ideally, you don't have any "unencapsulated" new in your code. > > Always > use > > boost::shared_ptr<T>(new T) or std::auto_ptr<>(new T) or any other > smart > > pointer. > > > > > Any suggestions? I'm not getting any errors from the interpreter. > > > > We need a complete reproducer. > > > > Cheers, > > Ralf > > > > > > > > > > __________________________________ > > Yahoo! Music Unlimited > > Access over 1 million songs. Try it free. > > http://music.yahoo.com/unlimited/

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Re: [C++-sig] Memory Leaks In VS.NET 2003 With BOOST_PYTHON_MODULE
by Matthew B. Keyes Oct. 13, 2005

Oct. 13, 2005

Sorry guys, it was late when I posted this, so the typo: return object(new CreateClassA()); Meant to be: return object(new A()); I was under the impression that the object class functioned as a reference counting auto_ptr of sorts... That solves that one for me. I'll post more later on the string issue 'cause I'm out of time right now. Thanks for the help! "Ralf W. Grosse-Kunstleve" <rwgk(a)yahoo.com> wrote in message news:<20051013155914.43599.qmail(a)web31505.mail.mud.yahoo.com>... > --- mjkeyes(a)sbcglobal.net wrote: > > > Hey again, I'm back. > > Hi Arnold! :) > > > Here is some pseudo-code of what I'm doing: > > Could you please turn this into a self-contained reproducer? Please explain > exactly how you compile and link. Note that you have to be very careful to not > mix debug and release builds under Windows. > > > class A > > { > > public: > > void SetString(const std::string &sVal) > > { > > m_sString = sVal; <--- Memory leak > > I am doing things like this all the time and I am sure it doesn't leak for me. > > > } > > > > void DoStuff() > > { > > SetString(msc_sString); > > } > > protected: > > static const std::string msc_sString; > > } > > Probably a side issue: do you really want "static" here? > > > > > class B > > { > > public: > > object CreateClassA() > > { > > return object(new CreateClassA()); <---- memory leak > > What is this? Does this even compile? > In any event, of course you get a memory leak if you use new like that. > Ideally, you don't have any "unencapsulated" new in your code. Always use > boost::shared_ptr<T>(new T) or std::auto_ptr<>(new T) or any other smart > pointer. > > > Any suggestions? I'm not getting any errors from the interpreter. > > We need a complete reproducer. > > Cheers, > Ralf > > > > > __________________________________ > Yahoo! Music Unlimited > Access over 1 million songs. Try it free. > http://music.yahoo.com/unlimited/

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Re: [C++-sig] Memory Leaks In VS.NET 2003 With BOOST_PYTHON_MODULE
by mjkeyes＠sbcglobal.net Oct. 13, 2005

Oct. 13, 2005

Hey again, I'm back. I've moved on to building an extension dll file in order to supplement my embedded application. Once again, I've got memory leaks. However, this is an easy one to test using your method of calling a function over and over. I did this and it chewed up the memory in my system like a hog (at least in task manager I see Python.exe growing steadily in memory consumption). Here is some pseudo-code of what I'm doing: class A { public: void SetString(const std::string &sVal) { m_sString = sVal; <--- Memory leak } void DoStuff() { SetString(msc_sString); } protected: static const std::string msc_sString; } class B { public: object CreateClassA() { return object(new CreateClassA()); <---- memory leak } } BOOST_PYTHON_MODULE(MyModule) { class_<A,boost::noncopyable>("ClassA") .def("DoStuff",&A::DoStuff) ; class_<B,boost::noncopyable>("ClassB") .def("CreateClassA",&B::CreateClassA) ; } Python: >>> from MyModule import * >>> A = ClassA() >>> A.DoStuff() <--- will call memory leak function >>> B = ClassB() >>> A = B.CreateClassA() <--- will call memory leak function Any suggestions? I'm not getting any errors from the interpreter. Thanks! "Ralf W. Grosse-Kunstleve" <rwgk(a)yahoo.com> wrote in message news:<20051010190642.45158.qmail(a)web31502.mail.mud.yahoo.com>... > --- mjkeyes(a)sbcglobal.net wrote: > > > Ralf (et. al), > > > > (note - I hope my newsgroup reader doesn't wrap all this in one > > line) > > > > I've been playing around with this and I'm still thinking boost > > leaks memory in an embedded and extended application. I use Visual > > Leak Detector 1.0 to track memory leaks, and here is where the leak > > comes from (in my code): ... > > If I insert VLDDisable() before this class_ block and VLDEnable() after > > (which temporarily disables the leak detection for this function call), > > I get zero leaks. With it turned on, here is what I see (repeated 17 > > times): > > ... > > d:\devl\muds\testbed\completelibtest\thirdlibtest\lib\pythoninputhandler > > .h (153): init_module_PyInputHandler > > 0x10006C2B (File and line number not available): > > boost::python::detail::exception_handler::operator= > > 0x1000EC23 (File and line number not available): > > boost::python::detail::init_module > > 0x1E0682B1 (File and line number not available): PyImport_FindModule > > 0x48747570 (File and line number not available): (Function name > > unavailable) > > Data: > > ... (whatever data leaked) > > I believe these leaks are not actually leaks, but a documented > (http://www.boost.org/libs/python/todo.html) feature of Boost.Python, > directly connected to the lack of support for PyFinalize(). I think > what you are seeing as leaks are actually just entries in the global > converter registry. These are one-time static allocations. Since you > cannot dlopen the same module multiple times there is no danger that > these allocations become a real problem. See also: > boost/libs/python/src/converter/registry.cpp > > Why is PyFinalize() support missing? -- Simply because the groups who > invested money into Boost.Python development had no interest in > embedding. > > To find real leaks, please consider my very simple approach of calling > the code with the suspected problem in an infinite loop while > monitoring the memory allocation of the process. Simple, quick, very > effective, works the same on all platforms. I've done it many times, > coincidentally a couple of days ago while testing new low-level code. > I didn't see any real leaks. > > Cheers, > Ralf > > > > > __________________________________ > Yahoo! Music Unlimited > Access over 1 million songs. Try it free. > http://music.yahoo.com/unlimited/

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setting up held smart pointer for pure virtual base class
by Scott McKay Oct. 13, 2005

Oct. 13, 2005

I have a pure virtual base class (so no_init is set). The base class is held by a smart pointer. I want to implement that class in python. I know that calling the __init__ function of the base class sets up the smart pointer that is held by boost::python. Is there some other way to set that up given the base class has no __init__ function? If it isn't setup I get an ArgumentError as the types don't match. If I make the base class virtual (by providing dummy implementations for what were the pure virtual functions) and call the __init__ everything works. Thanks Scott

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Nasty Heap Error in MSVC 7.1 With Boost and Python Using Derived Classes
by Matt Oct. 12, 2005

Oct. 12, 2005

Hey all, i'm trying to create an application that both embeds and extends python through boost. i've got a rough framework up and running, but now that i'm finally to the python part i'm having troubles. Please know that i'm a noob to boost and to boost.python, so if you see any obvious noob idiocies in my code please point them out (we've all got to start learning somewhere :)). Here's a rough run-down of my code: Base class (pure): template<class commandtype> InputHandler { public: /*...*/ virtual void Enter(commandtype *pOutput) = 0; }; Derived class: class PythonInputHandler : public InputHandler<std::string> { public: PythonInputHandler(PyObject *pSelf) : m_pSelf(pSelf) {} PythonInputHandler(const PythonInputHandler &rhs) : InputHandler<std::string>(rhs) //doesn't really do anything , m_pSelf(rhs.m_pSelf) { if(m_pSelf) Py_XINCREF(m_pSelf); } virtual ~PythonInputHandler() {Py_XDECREF(m_pSelf);} //overriden pure function: virtual void Enter(std::string *pOutput) { //this is where the nasty heap crash comes in, more below *pOutput = call_method<std::string>(m_pSelf, "Enter"); } } BOOST_PYTHON_MODULE(PyInputHandler) { class_<InputHandler<std::string>, PythonInputHandler, boost::noncopyable>("PythonInputHandler"); } Now, when the executable runs, this happens: if( PyImport_AppendInittab( "PyInputHandler", initPyInputHandler ) == -1 ) throw runtime_error("blah"); Py_Initialize(); PyObject *pInit = PyImport_ImportModule("Python.MyTest"); if(pInit == NULL) //...error handling PythonInputHandler *pHandler = new PythonInputHandler(call_method<PythonInputHandler>(pInit, "CreateInputHandler")); std::string sTest; pHandler->Enter(&sTest); //big heap crash Py_XDECREF(pInit); /*...*/ Here is the Python code: from PyInputHandler import * class PyLogonHandler(PythonInputHandler): def Enter(Output): return "Welcome from Python!" def CreateInitialHandler(): return PyLogonHandler() Now then, if i change "Welcome from Python!" to a shorter string, like "Hiya!", then it works, no error. As it stands, i get a _BLOCK_TYPE_IS_VALID error in what looks like the destructor of the std::string during the *pOutput = call_method... portion of the code (i'm assuming the destructor before the assignment to pOutput occurs). However, in the destructor, i do see the data consisting of "Welcome from Python!" Now i'm also a complete noob to boost and python. i've only been working on this for about 5 hours or so (the python side of things at any rate), so any tips to improve what i'm doing in addition to helping with this error is greatly appreciated. i'm finding it difficult to find some boost.python tutorials that are comprehensive enough. If you can't tell, i'm trying to expose a version of my InputHandler class to python so that it can be overriden and created from scripts instead of being hard-coded into the C++. Thanks for the help!!!!

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by jan.walter.berlin＠t-online.de Oct. 12, 2005

Oct. 12, 2005

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