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Re: [Boost-users] [filesystem] Using filesystem library from Boost version 1.44 on Cygwin 1.7
by Clarke, Carus V 30 Aug '10

30 Aug '10

> Date: Mon, 30 Aug 2010 08:36:49 -0700 > From: Steven Watanabe <watanabesj(a)gmail.com> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [filesystem] Using filesystem library from > Boost version 1.44 on Cygwin 1.7 > Message-ID: <4C7BD011.6010707(a)providere-consulting.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > AMDG > > Clarke, Carus V wrote: > > Steven Watanabe wrote: > >> Your code doesn't appear to print this last line. > > > > You are right. I added the last line after pasting in the > code. Here it is: > > > > boost_fs::file_status st = boost_fs::status(path, ec); > > <snip> > > std::cout << "Does file exist? " << boost_fs::exists(st) > << std::endl; > > return 0; > > } > > > > Is there anything I can do to make this work? > > > > It looks like stat is setting errno to ENOENT. > Do you get the same behavior if the file exists before > starting the program? > > In Christ, > Steven Watanabe > Yes, the behavior is the same whether the program writes the file or if the file had been previously written. Thanks, Carus V. (Bud) Clarke carus.v.clarke(a)boeing.com

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Boost.Serialization: Restoring object state (prevent creation of a new object)?
by ray＠maya-studio.com 30 Aug '10

30 Aug '10

If an object is serialized (saved) from a pointer, the loading part automatically creates (instantiates) a new object. However, there are situations when the object is already created and all we need is to restore its state. The following code demonstrates one possible - although not elegant - solution using a temporary object:#include <fstream> #include <iostream> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/serialization/string.hpp> #include <boost/serialization/export.hpp> class A { public: A() : m_val(100) { } int m_val; private: friend class boost::serialization::access; template <typename Archive> void serialize(Archive &ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(m_val); } }; int main(int argc, char* argv[]) { A *a = new A(); // Save the object { std::ofstream os("d:/test.xml"); boost::archive::xml_oarchive oa(os); // Save from pointer oa & BOOST_SERIALIZATION_NVP(a); } // Change the object state a->m_val = 200; // Restore the state { std::ifstream is("d:/test.xml"); boost::archive::xml_iarchive ia(is); A* aTemp; ia & BOOST_SERIALIZATION_NVP(aTemp); a->m_val = aTemp->m_val; // Copy object state assert(a->m_val == 100); delete aTemp; } } Here is my question: Is there some more convenient way to restore the object state? In other words, is it possible to prevent creation of a new object and just 'populate' an existing object?

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[filesystem] Using filesystem library from Boost version 1.44 on Cygwin 1.7
by Clarke, Carus V 30 Aug '10

30 Aug '10

Date: Fri, 27 Aug 2010 15:39:29 -0700 From: Steven Watanabe <watanabesj(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [filesystem] Using filesystem library from Boost version 1.44 on Cygwin 1.7 Message-ID: <4C783EA1.4070400(a)providere-consulting.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed AMDG Clarke, Carus V wrote: > I have been using the filesystem library from Boost version 1.43 on a Cygwin 1.7.6-1 platform without any problems. The library was built using the Cygwin version of GCC 4.3.4. The library from the 1.44 version of Boost compiles compiles o.k., but the functions that access files no longer work. This appears to be true for both versions 2 and 3 of the library. Below is a simple program that runs o.k. with the Boost version 1.43 version of the library. The program runs but can not read the file status using Boost version 1.44. This program also works fine when built using MSVC 9.0 and Boost version 1.44. > > //-------------------- > > <snip> > > int main() > { > <snip> > std::cout << "Error code message: " << ec.message() << std::endl; > return 0; > } > > //-------------------- > > This program's output on my system is shown below. The file 'foo' is written by the program and does actually exist. > > For version 2: > > boost::filesystem library version is v2 > Checking status of file foo... > Error code value: 0 > Error code message: The operation completed successfully > Does file exist? false > Your code doesn't appear to print this last line. In Christ, Steven Watanabe ------------------------------ You are right. I added the last line after pasting in the code. Here it is: boost_fs::file_status st = boost_fs::status(path, ec); <snip> std::cout << "Does file exist? " << boost_fs::exists(st) << std::endl; return 0; } Is there anything I can do to make this work? Thanks, Carus V. (Bud) Clarke carus.v.clarke(a)boeing.com ------------------------------

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[parameter] Weird behavior with bools
by Ryan McConnehey 30 Aug '10

30 Aug '10

I'm new to the parameter library and started with a simple example to get my feet wet. The first problem I'm having is with type restriction. The "name" variable is being restricted to a boolean type. This doesn't seem to be enforced since I can pass this variable a value of 15 and get this same value out. Currently my output has "name = 15" and I expected the output to be "name = 1". Did I not correctly enforce the type? The second problem is with the default value of my variable. I thought if the variable wasn't used then the third parameter, in the declaration, is used for instantiation of that variable. I thought that meant I could do this "m_name(args[_name])". The compiler gives an error saying the operator[] can't deduce the arguments. What did I not do that would allow this behavior. Thank you for your time in helping me out. Ryan BOOST_PARAMETER_NAME(name) struct myclass_impl { template <class ArgumentPack> myclass_impl(ArgumentPack const& args) : m_name(args[_name | false]) //: m_name(args[_name]) //gives a compile error { std::cout << "name = " << m_name << std::endl; } private: int m_name; }; struct myclass : public myclass_impl { BOOST_PARAMETER_CONSTRUCTOR( myclass, (myclass_impl), tag , (optional (name, (bool), bool(false)))) // no semicolon }; int main(int argc, char* argv[]) { myclass x(_name = 15); return 0; }

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Can I fstat or get the file date/time for a file stream ?
by Timothy Madden 30 Aug '10

30 Aug '10

Hello Is there a way to stat or to get file last accessed time from an opened std::fstream or boost::filesystem::fstream or a boost::iostreams::stream ? Or is there a way to get the underlaying file descriptor (or a FILE *) from a fstream so I can call POSIX fstat ? Thank you, Timothy Madden

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Fwd: Some trouble using mutexes
by Ernest Galbrun 30 Aug '10

30 Aug '10

Ok, thank you for your reply, I have been away for a week and I am back to work, with this problem still preventing my program to work fine. To answer your question, I have only one Robot in my project (for now) and the io_service is a Robot member. I now get why the active_count goes negative when the count goes up, but now I can't figure how it can ever be incremented twice. When debugging, I see the active_count being either 0, -2147483648, OR -2147483647. In fact, even when the active_count is not ==0, the lock() call returns instantly. Any clue ? Ernest Galbrun. > > Ernest Galbrun wrote: > > I would be really grateful if someone could give me a hint about what I > am > > doing wrong with the mutex and thread class (I am using boost 1.43, on > > windows XP running visual c++ 2010, the library has been built using the > > bjam utility). > > > > I have a main thread that creates an object of class robot : > > > > class Robot > > { > > private: > > boost::mutex tcpLock; > > boost::thread continuousThread; > > ... > > } > > > > Robot k3; > > > > this thread launches a thread that makes continuous calls to a member > > function of the robot. Since this function uses network ressources, I > want > > it to be safe so i use a lock The function called is the only function in > my > > program that uses this lock : > > > > int Robot::sendMsg(string msg, int n, vector<string>* answer) > > { > > tcpLock.lock(); > > (do stuff with the tcp io service) > > tcpLock.unlock(); > > return 0; > > } > > > > Of course, I also call this function from the main thread. > > > > And I have disruptive behavior, which I don't understand. > > Do you have multiple Robots? Is the io_service shared between them? > > > When debugging, I > > see that the 'active_count' of the tcpLock object stays negative or ==0, > > which seem absolutely wrong to me, but I don't understand how it could > ever > > be anything other than 0 or 1. > > > > The implementation indicates that the mutex is locked with the > high-order bit, which means that a locked mutex will have > a negative active count. > > In Christ, > Steven Watanabe >

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boost transfer pointers by serialize
by Jack Bryan 29 Aug '10

29 Aug '10

Dear All, I need to transfer some pointers from one process to another process on Open MPI cluster. These pointers are members of a class. They are like: class myClass{double *;int *;double**; } When I use serialize in boost , I got errors: /boost/serialization/access.hpp:118: error: request for member âserializeâ in âtâ, which is of non-class type âdoubleâ Any help is appreciated. JACK Aug. 29 2010

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boost thread - bug pthread
by Kraus Philipp 29 Aug '10

29 Aug '10

Hi, I'm writing a multithread application and I test my program with valgrind. I create a thread group and valgrind shows this message: ==4608== Thread #1: Bug in libpthread: recursive write lock granted on mutex/wrlock which does not support recursion ==4608== at 0x503FC: pthread_cond_wait* (hg_intercepts.c:653) ==4608== by 0x19C3B7: boost::thread::join() (in libboost_thread.dylib) ==4608== by 0x15D8C: boost::thread_group::join_all() (in ./main) I use Boost 1.44 on OSX 10.5. How can I solve this "Bug"? Thanks Phil

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string algo - documentation bug?
by mafeusek＠gmail.com 29 Aug '10

29 Aug '10

Hallo Group Members. in http://www.boost.org/doc/libs/1_44_0/doc/html/string_algo/concept.html I can read: * Function Finder. Finder can be any function object. That is, any ordinary function with the required signature can be used as well. However, such a function can be used only for a specific iterator type. boost::iterator_range<std::string> simple_finder( std::string::const_iterator Begin, std::string::const_iterator End ) { return boost::make_range( Begin, End ); } but following code does not compile: #include <iostream> #include <string> #include <boost/algorithm/string.hpp> #include <boost/range.hpp> int main(int argc, char *argv[]) { boost::iterator_range<std::string> dd; return 0; } As I understand, I need to put iterator as template parameter to iterator_range, thus: #include <iostream> #include <string> #include <boost/algorithm/string.hpp> #include <boost/range.hpp> /* boost::iterator_range<std::string> simple_finder( std::string::const_iterator Begin, std::string::const_iterator End ) { return boost::make_range( Begin, End ); } */ int main(int argc, char *argv[]) { boost::iterator_range<std::string::iterator> dd; return 0; } compiles ok. Is it documentation bug? best regards, Pawel

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Any stream class for C standard FILE * streams ?
by Timothy Madden 29 Aug '10

29 Aug '10

Hello Is there a stream class in boost that would use a C standard FILE * stream as the buffer ? Thank you, Timothy Madden

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