July 2009 - Boost-users - lists.preview.boost.org

[utility] Anyone here using Intel 9.0 compiler + value_initialized?
by Niels Dekker - address until 2010-10-10 04 Jul '09

04 Jul '09

boost::value_initialized<T>, as included with the release version of Boost (current version: 1.39.0), has a conversion operator that breaks the principle of "logical constness": The member function itself is "const", but it returns a non-const reference to the data, T&. Four months ago, I fixed this issue on the development trunk [51355], replacing the conversion operator by a const and a non-const overload. The const overload returns a const reference to the data. (Ticket #2548.) After this fix, one specific version of a compiler yielded some compiler errors at the regression page: Intel 9.0 In fact it only yielded two compiler errors: only for implicitly conversions from value_initialized<NonPOD*>, and const value_initialized<NonPOD*>. Other conversions went well, for example, from const value_initialized<int> to const int&. Now I wonder, because Intel 9.0 is an old compiler version, and the regression failure occurs only in a very specific case, would it be acceptable to leave the fix in there, and have it shipped with an upcoming release version of Boost? Is anyone here likely to use the next version of Boost, including value_initialized<T>, on Intel 9.0? If so, would you find it acceptable to retrieve a reference to the data from value_initialized<T> by using the value_initialized::data() member function, or boost::get, instead of depending on implicit conversion? Note: Five days ago I committed a workaround for Intel 9.0 to the trunk [54502], removing the const-version of the overload. But it yielded many more Intel 9.0 errors (33!), as expected, on any attempt to convert a const value_initialized<T>. So does anyone here think this workaround is still useful? References: Ticket #2548, "Let's fix the logical constness of value_initialized!" https://svn.boost.org/trac/boost/ticket/2548 Utility/trunk regression page: www.boost.org/development/tests/trunk/developer/utility_.html [51355] Fix at the development trunk (4 months ago): https://svn.boost.org/trac/boost/changeset/51355 [54502] Intel 9.0 specific workaround (5 days ago): https://svn.boost.org/trac/boost/changeset/54502 Kind regards, -- Niels Dekker http://www.xs4all.nl/~nd/dekkerware Scientific programmer at LKEB, Leiden University Medical Center

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[Boost.Test] [1.38] Handling unexpected exceptions and system errors
by Greg Christopher 04 Jul '09

04 Jul '09

Hi, One of the things that sets boost apart from other frameworks is its ability to handle exceptions and report them. While I've used the BOOST_CHECK_THROW and BOOST_CHECK_EXCEPTION macros, I'd like a way to pass if an exception is thrown that we don't necessarily understand how to mention in the BOOST_CHECK_THROW or BOOST_CHECK_EXCEPTION macros. BOOST_CHECK_NO_THROW just makes sure no exception is thrown. In some ways it's an odd request to say "I expect some exception to be thrown that I do not care to specify", but that would work for us. In addition, it would be nice (and I bet it's already available) to be able to say "allow next test case to run in event of exception" or "allow next test suite to run In event of exception". Right now, all testing does seem to abort (none of the above macros are either present or coded in a way to match the system issue. Any tips on how to discover those values, or to go forward when some kind of exceptional condition is expected is appreciated. -Greg

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Query on implementing a lock manager
by dhruva 04 Jul '09

04 Jul '09

Hello, I am looking for a centralized or distributed lock manager. My needs are simple. I have names for each shared resource, I want to have advisory reader and writer locks on those named resources. I can implement it by having a server which serves all the lock requests. Each named lock will be a boost reader writer lock (which are implemented using atomic operations). Since lock requests come over TCPIP, the client (lock requester) will block till the server sends a response. Using non blocking sockets, the client can have a lock with time outs or async locks. If there is something similar available, I rather reuse than implement it from scratch. This requirement is to have some locking on files that intend to share using NFS and CIFS. Since NFS and CIFS servers are different, I will not get a common lock manager. I do not need sophisticated byte rane locking (fcntl), just a reader/writer lock on the file would do. Also, I ensure that the part of file path is unique and common across shares. This can be used as the resource name across the network. Any suggestions, ideas or links would be of real help. -dhruva Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com

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[Proto] Recreating an expression
by christophe henry 03 Jul '09

03 Jul '09

Thanks Eric for your fast answer! Unfortunately, this doesn't solve my problem. To make a very very long discussion long, here a small example showing the problem from another side: I have an expression wrapper called mp_terminal and I define terminals, but not in the documented way (which I suspect is the problem) but instead deriving from them (for convenience purposes), for example: struct True : mp_terminal<typename proto::terminal<guard_tag>::type> {...} These terminals are used with a simple grammar: struct BuildGuards : proto::or_< proto::when< proto::logical_or<BuildGuards,BuildGuards >, GuardOR<BuildGuards(proto::_left),BuildGuards(proto::_right)>() >, proto::when< proto::logical_and<BuildGuards,BuildGuards >, GuardAND<BuildGuards(proto::_left),BuildGuards(proto::_right)>() >, proto::when< proto::logical_not<BuildGuards >, GuardNOT<BuildGuards(proto::_value)>() >, proto::when < proto::terminal<guard_tag>, proto::_() > > {}; Then, expressions like: True()|| False() give the expected result (struct GuardOR<struct True,struct False>). Even True()&& (Dummy1() || !(False() || True())) give the expected result: struct GuardAND<struct True,struct GuardOR<struct Dummy1,struct GuardNOT<struct GuardOR<struct False,struct True> > > > But a "!" alone (meaning followed by just a terminal, not the other parts of the BuildGuards grammar) breaks all (as do all unary operators I tried), like !False() or True()|| !False(). !False() => struct GuardNOT<struct mp_terminal<struct boost::proto::exprns_::expr<struct boost::proto::tag::terminal,struct boost::proto::argsns_::term<struct guard_tag>,0> > > Notice that !(False() || True()) works! Now, if I do not derive from mp_terminal but instead proceed as documented, all works as expected: proto::terminal<True>::type True_; ... !False_ => correct result. Sadly, this documented usage is unpractical in my use case. So, supposing that I managed this easy grammar, I imagine that the usage I do of terminals (deriving from them) is not allowed. Then, why do most use cases work like a charm? Only unary operators seem to fail. Attached are 2 test files. V1 doesn't work in all cases while V2 does. I use 1.38. Thanks a lot! Christophe _________________________________________________________________ Windows Live™: Keep your life in sync. Check it out! http://windowslive.com/explore?ocid=TXT_TAGLM_WL_t1_allup_explore_012009

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detect if a type has a size_t member
by Hicham Mouline 03 Jul '09

03 Jul '09

Hello template <typename T> struct S { // how to detect T has a member static const size_t value ? // if T has value, define member of S, m1 of type T1, otherwise m2 of type T2 }; Regards,

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[Units][Interval] Using both together
by Anubis 03 Jul '09

03 Jul '09

Hello all! First let me congratule Matthias and Steven for the great units library. Just recently I have kicked out my own attempt at something like it and switched to boost::units. However I ran into trouble using both boost::units and boost::interval because a single int cannot be static casted to a quantity. So one could either provide a function like: static boost::units::quantity<Unit,Y> quantity(int aValue) { boost::units::quantity<Unit,Y>::from_value(aValue); } Probably not the best idea as any value would get casted to a quantity without notice, therefore totally ruining the concept of from_value. Or as I have implemented a specific checking policy for boost::interval: #include <boost/numeric/interval.hpp> //! The checking policy for boost::interval, if it uses boost::unit /*! Look into boost/numeric/interval/checking.hpp to see other possible base checking policies for template parameter Checking */ namespace boost { namespace units { namespace interval_support { template<class T, class Checking = boost::numeric::interval_lib::checking_base<T> > struct checking_base : Checking { static T empty_lower() { return (std::numeric_limits<T>::has_quiet_NaN ? std::numeric_limits<T>::quiet_NaN() : T::from_value(1)); } static T empty_upper() { return (std::numeric_limits<T>::has_quiet_NaN ? std::numeric_limits<T>::quiet_NaN() : T::from_value(0)); } }; }}} And actually use it like this: #include <boost/units/interval_support.hpp> // or whichever name typedef boost::numeric::interval_lib::change_checking< boost::numeric::interval<MY_QUANTITY_TYPE>, boost::units::interval_support::checking_base<MY_QUANTITY_TYPE> >::type my_unit_interval_type; HTH to easily use boost::units and boost::interval in the future, Thomas Taylor

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Re: [Boost-users] [smart_ptr] weak_ptr / shared_ptr interaction
by Alexander Heinrich 03 Jul '09

03 Jul '09

> Both s1 and s2 should now have use_count of 2 at this point, since there > are 2 shared_ptrs sharing ownership of the same pointee. > > The post-condition expression is correct; the value of r.use_count() > was changed by the construction of the new shared_ptr. Thanks for your reply. So you're saying that the behavior of shared_ptr is correct (perfectly fine with me). But then I have to say, that the documentation of shared_ptr located under http://www.boost.org/doc/libs/1_39_0/libs/smart_ptr/shared_ptr.htm#construc… is wrong, because it says that if you construct a shared_ptr from a weak_ptr (!) the use_count will *not* change.

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Problems with De/Serializing data structures with dll
by Grimm 03 Jul '09

03 Jul '09

Hi, I'm quite noob with boost and I wrote a little test program to test how boost handles serialization of data structures and deserializing the data in dll-plug-in. ( In this case only linked list of BaseImplementation objects, but if I got everything OK more complex structures is need to be serialized). It seems that I have(surprisingly) some problems with de/serializing list properly maybe cause of m_next pointers. I've read the documentation, but not have found help for this issue. Here's some relevant parts of my code ( I know It's a bit ugly, but hey! It's only for test purposes :) : Base.h: /* Abstract base class declaration of objects in linked list*/ #ifndef BASE_H #define BASE_H #include <string> #include <iostream> #include <boost/serialization/assume_abstract.hpp> class Base { public: Base(){} virtual ~Base(){} virtual void setID(const int a_id) =0; virtual const int getID() const =0; virtual void setValue( const double a_value ) =0; virtual const double getValue() const =0; virtual void setDescription( const std::string a_desc ) =0; virtual const std::string getDescription() const =0; virtual void setNext( Base* a_next ) =0; virtual Base* getNext() =0; //Operation - prints some information regarding the object virtual void print()const =0; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { } }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(Base) #endif ###################################### BaseImplementation.h: //Implementation of Base-class (cells of linked list) #ifndef BASEIMPLEMENTATION_H #define BASEIMPLEMENTATION_H #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> //#include <boost/serialization/export.hpp> #include <boost/serialization/base_object.hpp> #include <boost/serialization/utility.hpp> #include "Base.h" class BaseImplementation : public Base { public: //Constructor & Destructor BaseImplementation(); BaseImplementation( int a_id ); ~BaseImplementation(); //setter & getter virtual void setID( const int a_id ); virtual const int getID() const; virtual void setValue( const double a_value ); virtual const double getValue() const; virtual void setDescription( const std::string a_desc ); virtual const std::string getDescription() const; virtual void setNext( Base* a_next ); virtual Base* getNext(); //Operation - print virtual void print() const; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & boost::serialization::base_object<Base>(*this); ar & m_id; ar & m_value; ar & m_desc; //THIS SEEMS TO BE THE PROBLEM!!! ar & m_next; } int m_id; double m_value; std::string m_desc; Base* m_next; }; //BOOST_CLASS_EXPORT_GUID(BaseImplementation, "base_impl") #endif ############################################### main program: // PluginTest.cpp : Defines the entry point for the console application. #include "stdafx.h" #include "PluginInterface.h" #include "BaseImplementation.h" #include <iostream> #include <fstream> #include <ctime> #include <cstdio> int _tmain(int argc, _TCHAR* argv[]) { std::remove("serialized.plop"); ...foo... ...foo.. ...foo.. //--Serialization-------------------------------------------------- std::ofstream ofs("serialized.plop"); boost::archive::text_oarchive oa(ofs); BaseImplementation* myObject = NULL; Base* first = NULL; BaseImplementation* prev = NULL; Base* tmp = NULL; //starting point of time consumption calc. start = clock(); //Let's create linked list of 114 instances of //BaseImplementation for dll to deserialize for(int i=0; i < 114; i++) { myObject = new BaseImplementation(); //sets the next cell of the list if(prev) { prev->setNext(myObject); } //first cell of linked list else { first = myObject; tmp =myObject; } //sets the data for object myObject->setID( i ); myObject->setValue( 0.5 +(double)i ); myObject->setDescription("This is object"); prev = myObject; } //The serialization itself oa.register_type(static_cast<BaseImplementation *>(tmp)); for(int i=0; i < 114; i++) { oa << tmp; tmp = tmp->getNext(); //oa << *tmp; } //oa << first; ofs.close(); //Deallocates created & serialized objects for(int i=0; i < 114; i++) { tmp = first->getNext(); delete first; first =tmp; } //stop time consumption calc. stop = clock(); //time consumption of serialization long serializationTime = ( stop - start ); //---Serializatio ends here----------------------------------------- //---Deserialization------------------------------------------------ //start the clock start = clock(); //Deserializes the linked list created above for dll-plugin thePlugin->load("serialized.plop"); //stop the clock stop = clock(); //time consumption of deserialization long deserializationTime = ( stop - start ); //Prinst some deserialized data thePlugin->print(50); std::cout <<"Serializations takes: " <<serializationTime <<" ms" <<std::endl; std::cout <<"Deserialization takes: " <<deserializationTime <<" ms" <<std::endl; ########################################################## Definition of thePlugin class: #include ".\cmyplugin.h" cMyPlugin::cMyPlugin() : cIHAPlugin() { m_name = "My plugin!"; m_description = "A plugin which is located in DLL!"; BaseImplementation* m_baseImpl = NULL; } cMyPlugin::~cMyPlugin() { } bool cMyPlugin::install(cIHAPluginCoreInterface* a_pluginCore) { std::cout << "installing plugin.. "; if( !a_pluginCore ) { std::cout << "failed!\n"; return false; } std::cout << "success.\n"; return true; } /*! \brief Gets the plugin name. \return The plugin name. */ const char* cMyPlugin::getName() { return m_name.c_str(); } /*! \brief Gets the plugin description. \return The plugin description. */ const char* cMyPlugin::getDescription() { return m_description.c_str(); } const int cMyPlugin::getNumber() { return m_baseImpl->getID(); } void cMyPlugin::load(std::string file) { //opens archive std::ifstream ifs(file.c_str()); boost::archive::text_iarchive ia(ifs); ia.register_type<BaseImplementation>(); //this doesn't handle pointers to next cell in list ia >> m_baseImpl; ifs.close(); } void cMyPlugin::print(int a_index) { m_first =m_baseImpl; Base* tmp =m_first; if( !m_first ) { std::cout << "ULTIMATE ERROR!!" << std::endl; return; } else { std::cout <<"--- This is value(double) of first cell: "; std::cout << m_first->getValue() <<" ---" <<std::endl; std::cout <<"--- This is value(double) of second cell: "; std::cout <<m_first->getNext()->getValue() <<" ---" <<std::endl; } for(int i=0; i < 114; i++ ) { if(i == a_index ) { tmp->print(); break; } tmp =tmp->getNext(); } } ################################################## Ok, this works still fine with 114 or less instances on the list, but when I try to do this with more than 114 instances it fails on line: oa << tmp; when it's called for first time. Error Message: "Unhandled exception at 0x1029dfdc (msvcr90d.dll) in SerializationTest.exe: 0xC00000FD: Stack overflow." I had to implement the deserialization in dll's load()-method cause it worked even worse with Serialize(...) used in documentation/examples I use Visual Studio 2008 and boost1.38 by the way. I "solved" this problem by not de/serializing the next pointer(for linked list) and constructed(set the next pointers) the list with own hands while deserializing. But thats possible only cause of simple structure of linked list and it will not work with more complex structures. Any ideas what I'm doing wrong in code I pasted above and how I get it work? And is serialization of tree-like data structures even possible with dlls involved? Thank you! ps: BOOST_CLASS_EXPORT_GUID() macro which is now commented away caused some weird linking errors. -- View this message in context: http://www.nabble.com/Problems-with-De-Serializing-data-structures-with-dll… Sent from the Boost - Users mailing list archive at Nabble.com.

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[smart_ptr] weak_ptr / shared_ptr interaction
by Alexander Heinrich 03 Jul '09

03 Jul '09

Hi @ boost-users. The documentation of shared_ptr states the following: <quote> template<class Y> explicit shared_ptr(weak_ptr<Y> const & r); Effects: Constructs a shared_ptr that shares ownership with r and stores a copy of the pointer stored in r. Postconditions: use_count() == r.use_count(). </quote> Now I experienced some odd behavior with the following piece of code: <code> boost::shared_ptr<int> s1(new int(42)); // use_count == 1 boost::weak_ptr<int> w(s1); // use_count == 1 boost::shared_ptr<int> s2(w); // use_count == 2 (expected use_count == 1) boost::shared_ptr<int> s3 = s2; // use_count == 3 (not sure what to expect here...) </code> 1) According to the documentation use_count should still be 1 after instantiating s2, but it is 2. Or did I misinterpret the docs? 2) Independent of whether instantiating s2 increments the use_count or not, I am unsure if assigning (or copying) a shared_ptr that was constructed from a weak_ptr should increment the use_count (see s3). I'd appreciate any comments on this. Best regards, Alexander

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[Spirit] chset_p
by Commander Pirx 03 Jul '09

03 Jul '09

Hi all, I've detected a strange behavior of Spirit using (VC9SP1). I assume that chset_p( "-_!#$%&*+|~" ) and chset_p( "!#$%&*+-_|~" ) are identical. I've only changed the order of the characters a little bit. But when i'm trying to parse a string like "abcd-edfg: " the parser eats the ':' sign but shouldn't. Examples here: token_ = alnum_p | chset_p( "-_!#$%&*+|~" ); // the line above works fine token_ = alnum_p | chset_p( "!#$%&*+-_|~" ); // here the ':' sign will be consumed! Thanx.

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