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[statechart] StopWatch aborts on context<StopWatch>()
by jeti 05 Mar '09

05 Mar '09

hi all im pretty sure i just dont understand what context<>() really does and how it works reading the docs/tutorial doesnt seem to help me so, can someone point me to a documentation for boost::statechart and how to get a Pointer/Reference to the currents state_machine from a simple_state? what do i have to keep in mind? just to give an example: if i add the following line in the boost/libs/statechart/examples/StopWatch/StopWatch.cpp file Running() : startTime_( std::time( 0 ) ) { context<StopWatch>(); // <<< added } it compiles and abort's if i try to start the stopwatch i dont understand why? the state_machine is initialized and even the docs say in its comments that i can use it to get the statemachine http://www.boost.org/doc/libs/1_38_0/libs/statechart/doc/tutorial.html#Stat… but im sure i just miss something any help on this would be great thanks in adavance

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[signals2] Usage (lifespan) question
by Nat Goodspeed 05 Mar '09

05 Mar '09

I'd like suggestions for an API designed around Boost.Signals2. This isn't performance-critical. Assume a publish class containing a boost::signals2::signal. This class's listen() method is a thin wrapper around signal::connect(). Using boost::bind, I can listen() with any method (with appropriate signature) on any class. I'm trying to introduce the concept of filter objects. Each filter is itself a publish object. Client logic composes a chain from some publish object through zero or more filters to the ultimate listener. A filter passes along to its own listeners some subset of the input notifications. The central issue is the lifespan of a filter object. I want the filter objects in such a chain implicitly freed when the ultimate listener disconnects. Approach 1 ========== I could achieve that by managing each filter object with shared_ptr, storing a copy in each listener. When the last listener is destroyed, the filter goes away. (This assumes passing weak_ptr to boost::bind() so the connection itself doesn't keep the listener alive. Further assume I've used connection::track() so that the signal to which the filter is connected implicitly disconnects.) Naturally this effect cascades "upstream" through the filter chain. But it bothers me that such an implementation imposes new requirements on each listener. Beyond declaring a method with the right signature, the listener must now store a shared_ptr to the publish object to which it's listening. That implies a method on the listener to capture the shared_ptr and establish the connection. Therefore, every listener must be derived from some particular base class, and explicit connection and disconnection must be done through the listener rather than directly through the publish object. Either this new inverted API must apply to all publishers/listeners, or client logic must distinguish between the case of connecting to a filter and connecting to any other type of publish object. It feels to me as though this approach has gone into the weeds. Approach 2 ========== Instead of passing a filter's weak_ptr to boost::bind() to the publish object's listen() method, I could instead pass the filter's shared_ptr. Now the publish object upstream from the filter is responsible for the filter's lifespan: when the filter explicitly disconnects, it will (eventually) go away. It will not implicitly disconnect because it won't go away as long as the connection still holds a copy of its shared_ptr. (Frank says[1] he might tweak the library to forget a shared_ptr immediately on disconnect, but currently it survives for a while.) Consider a chain: A is the original publish object B is a filter listening to A C is the ultimate listener, listening to B Again, the goal is to disconnect B (thus deleting it) when C disconnects or is destroyed. We could make B store its connection object to A. The question is, how would B know to disconnect it? How could B become aware of C disconnecting from B's signal object? Approach 3-n ============ Suggestions? Thanks! [1] http://www.nabble.com/Re%3A--signals2--review--The-review-of-the-signals2-l…

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[Serialization] Load an object from the base pointer
by Ryan Fowler 05 Mar '09

05 Mar '09

Hi, How can I read in a from a stream when I don't know the exact type I will be getting? All objects I receive will derive from the same base class, but I won't know when I receive the stream what the derived type will be and therefore I can't create it in advance (like in the docs). class base { ... } class derived1 : public base { ... } class derived2 : public base { ... } int main() { // Get a stream from somewhere boost::archive::binary_iarchive ia( instream ); base b0; derived1 d1; derived2 d2; is >> // derived1 or derived2??? } Ryan Fowler Software Engineer Thomson Reuters Phone: +442075427063 ryan.fowler(a)thomsonreuters.com thomsonreuters.com This email was sent to you by Thomson Reuters, the global news and information company. Any views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of Thomson Reuters.

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Microsoft compiler bug: Boost 1.38 smart pointers + CLI = crash
by Oleg Golosovskiy 05 Mar '09

05 Mar '09

I have added a new bug to connect.microsoft.com. I can send the sample project if anybody needs it. https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?Feedb… Type Bug ID 420897 Status Active Access Restriction Public Opened By OlegGL Blocking Issue No Opened 3/5/2009 Submission Language English ------------------------------------------------------------------------ *Description * The problem looks identical to one described in bug #101889. http://connect.microsoft.com/VisualStudio/feedback/Workaround.aspx?Feedback… There is only one difference - intrusive_ptr instead of shared_ptr originally reported in #101889 The code bellow causes assertion: boost::intrusive_ptr<test_ptr> ptr; if(ptr) assert(false); //MUST NOT HAPPEN BUT IT DOES! Reproduced on VS2005 SP1 and VS2008 SP1 (Windows XP SP2) Boost 1.38 To reproduce the problem, the Boost (booost/smart_ptr.hpp in our case) shall be included in the CLI-compiled file under #pragma managed (push,off) (see the code below) If changed to "#pragma managed (push,on)", then everything is fine Product Language English Version Visual Studio 2008 SP1 Operating System Windows XP Professional Operating System Language English *How to reproduce: *Create any native win32 C++ project, for example a console based. int _tmain(int argc, _TCHAR* argv[]) { do_test(); return 0; } 1) Install and compile BOOST 1.38 2) Add a new CPP file to the project. This file has a minimal intrusive pointer "environment" and a code check. The Code is below. 3) Set /clr option for that particular file (Common Language Runtime Support in the Options) 4) build the project #include "stdafx.h" #include "test3_dll.h" #pragma managed (push,off) #include "boost/smart_ptr.hpp" class intrusive_ptr_base1 { friend void intrusive_ptr_add_ref(intrusive_ptr_base1*); friend void intrusive_ptr_release(intrusive_ptr_base1*); size_t m_ref_counter; void add_ref() { ++m_ref_counter; } void release() { if (--m_ref_counter == 0) delete this; } protected: intrusive_ptr_base1() : m_ref_counter(0) {} virtual ~intrusive_ptr_base1() {} intrusive_ptr_base1(intrusive_ptr_base1 const &) :m_ref_counter(0) {} intrusive_ptr_base1 &operator=(intrusive_ptr_base1 const &) { return *this; } }; inline void intrusive_ptr_add_ref(intrusive_ptr_base1* e) { e->add_ref(); } inline void intrusive_ptr_release(intrusive_ptr_base1* e) { e->release(); } class test_ptr : public intrusive_ptr_base1 { }; #pragma managed (pop) void do_test() { boost::intrusive_ptr<test_ptr> ptr; if(ptr) assert(false); } Actual Results if(ptr) returns true for the empty ptr! Expected Results if(ptr) must return false for the empty ptr TAP Code (if applicable)

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[boost::program_options] Different usage
by Everton Patitucci 05 Mar '09

05 Mar '09

Hello, I'm wondering if I should use boost::program_options and I got some questions about it. All examples that I found are using std::string and std::ostream everytime they're dealing with values being some kind of text... so to display the "usage" of their program they would do something like... cout << desc; 'desc' being a boost::program_options::options_description. or... when adding options to their command line... desc.add_options() ... ("opt", boost::program_options::value<std::string>, "desc") ... What I want to know is, if I didn't want to use std::string nor std::ostream nor std anything in my specific code (I know boost uses it). Is there a not-so-time-expensive way to do it? If there's could someone show me (there's no need for the real code, pseudo is more than OK) if it's supported? something like this for example... desc.add_options() ("opt", bpo::value<char*>, "blabla") and in usage()-like: I don't know if this works, I looked in doc... std::vector< shared_ptr<po::option_description> > opts = desc.options(); std::vector< shared_ptr<po::option_description> >::iterator it = opts.begin(); for (; it != opts.end(); ++it) { shared_ptr<po::option_description> opt = *it; printf("%s\n", opt->format_parameter().c_str()); } Patuti

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[asio] serial port howto?
by Markus Werle 05 Mar '09

05 Mar '09

Hi! For first time users of asio it is not easy to get things started. I found a demo application (minicom_client) on the web, but it uses a raw io_service. In the reference docs I found serial_port_service. What is the difference? Can I use serial_port_service as a drop in replacement where an io_service normally is used? Is there any small example how to use all this? best rgards, Markus

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[boost::mpl][boost::variant]
by Naveen Santhanam 05 Mar '09

05 Mar '09

Hello, I can't get the attached example to compile, using MS VC 8.0 and boost_1_35_0, when I uncomment the comment lines in the code. Can some one help me in finding what's wrong? A brief description: The code contains a class that has a variant as a member and a visitor that creates types of the variant. Thanks in advance

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Boost thread priority
by Andrei VANCEA 05 Mar '09

05 Mar '09

Hello! I want to set the priority of a boost thread. It seems that this feature is not (yet) implemented and the only option is to go to lower level (pthread in my case). The documentation says that the method native_handle() should return the handler of the associated pthread. The problem is that this method no longer exists (for the pthread implemention; it is there for the win32 version). Anyone knows how to get the pthread handler of a boost thread (I'm using the 1.35 vesion) -- Andrei Vancea

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Re: [Boost-users] [auto_link] Using MSVC 2005 (VC8)
by dhruva 05 Mar '09

05 Mar '09

Apologize for the false alarm, I was using CMake generated files to build. After making cnahes in the CMake file, I had missed regenerating the MSVC build files... Everything's fine and it works at it always does :) -dhruva ----- Original Message ---- > From: dhruva <dhruva(a)ymail.com> > To: BOOST users <boost-users(a)lists.boost.org> > Sent: Thursday, 5 March, 2009 12:04:41 PM > Subject: [auto_link] Using MSVC 2005 (VC8) > > Hi, > I have built boost 1.38 using MSVC 2005 using "--layout=system link=static". > That has resulted in libraries with the following name convention. > > libboost_system-mt.lib > libboost_date_time-mt.lib > > Auto link triggers in even if I define BOOST_ALL_NO_LIB. I searched through the > all of BOOST headers in my install folder for BOOST_ALL_NO_LIB and found it only > in a comment in boost/config/user.hpp > > Would that define really disable auto-link? > > -dhruva > > > > Check out the all-new Messenger 9.0! Go to http://in.messenger.yahoo.com/ Check out the all-new Messenger 9.0! Go to http://in.messenger.yahoo.com/

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[auto_link] Using MSVC 2005 (VC8)
by dhruva 05 Mar '09

05 Mar '09

Hi, I have built boost 1.38 using MSVC 2005 using "--layout=system link=static". That has resulted in libraries with the following name convention. libboost_system-mt.lib libboost_date_time-mt.lib Auto link triggers in even if I define BOOST_ALL_NO_LIB. I searched through the all of BOOST headers in my install folder for BOOST_ALL_NO_LIB and found it only in a comment in boost/config/user.hpp Would that define really disable auto-link? -dhruva Check out the all-new Messenger 9.0! Go to http://in.messenger.yahoo.com/

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