August 2008 - Boost-users - lists.preview.boost.org

[dataflow.signals][thread_safe_signals] How to alter the Calling of chained signals
by Manuel Jung 07 Sep '08

07 Sep '08

Hi! I want to use dataflow.signals, which is build on top of thread_safe_signals. Each call of a producer (each signal) is put into a threadpool. Now i want not to execute the whole chain of data processing at once, but just one chain link at the time and put a new task to the threadpool than. The goal is that i can put rather complex and long (running) dataflow chains in the threadpool, which are divided into many pieces, so the threadpool can often decide which task is most important. So how can i alter the call of the next signal in a signal network/chain? Kind regards Manuel

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Cannot statically link to Boost.Filesystem
by Graham Bull 05 Sep '08

05 Sep '08

Hi all, I've got this really simple C++ program that's using the Boost.Filesystem library: #include <iostream> #include <boost/filesystem.hpp> int main() { boost::filesystem::path pathname = "/usr/local/bin"; std::cout << pathname.string() << std::endl; return 0; } It compiles fine, and I can get it to link to use the shared object: g++ -I/usr/local/include/boost-1_35 -o test test.cpp -lboost_filesystem-gcc42-mt-1_35 But I want to statically link instead. I've tried this and other similar combinations: g++ -I/usr/local/include/boost-1_35 -o test test.cpp -lboost_filesystem-gcc42-mt-s-1_35 -static -static-libgcc and I'm always getting these linker errors: /tmp/ccoiFv2v.o: In function `__static_initialization_and_destruction_0(int, int)': test.cpp:(.text+0x1dc): undefined reference to `boost::system::get_system_category()' test.cpp:(.text+0x1e6): undefined reference to `boost::system::get_posix_category()' test.cpp:(.text+0x1f0): undefined reference to `boost::system::get_posix_category()' test.cpp:(.text+0x1fa): undefined reference to `boost::system::get_system_category()' collect2: ld returned 1 exit status I've built Boost in full and have got these Boost.Filesystem libraries in /usr/local/lib: libboost_filesystem-gcc42-1_35.a libboost_filesystem-gcc42-1_35.so libboost_filesystem-gcc42-1_35.so.1.35.0 libboost_filesystem-gcc42.a libboost_filesystem-gcc42-d-1_35.a libboost_filesystem-gcc42-d-1_35.so libboost_filesystem-gcc42-d-1_35.so.1.35.0 libboost_filesystem-gcc42-d.a libboost_filesystem-gcc42-d.so libboost_filesystem-gcc42-mt-1_35.a libboost_filesystem-gcc42-mt-1_35.so libboost_filesystem-gcc42-mt-1_35.so.1.35.0 libboost_filesystem-gcc42-mt.a libboost_filesystem-gcc42-mt-d-1_35.a libboost_filesystem-gcc42-mt-d-1_35.so libboost_filesystem-gcc42-mt-d-1_35.so.1.35.0 libboost_filesystem-gcc42-mt-d.a libboost_filesystem-gcc42-mt-d.so libboost_filesystem-gcc42-mt-s-1_35.a libboost_filesystem-gcc42-mt-s.a libboost_filesystem-gcc42-mt-sd-1_35.a libboost_filesystem-gcc42-mt-sd.a libboost_filesystem-gcc42-mt.so libboost_filesystem-gcc42-s-1_35.a libboost_filesystem-gcc42-s.a libboost_filesystem-gcc42-sd-1_35.a libboost_filesystem-gcc42-sd.a libboost_filesystem-gcc42.so I hope someone can help me because I just can't see what I'm doing wrong! Graham

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mutex locking!
by Wesley Khandavalli 05 Sep '08

05 Sep '08

I want to explicitly lock and unlock mutex. Is it possible and what are the methods? -- Wesley K

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[bjam] Presence of Mac OS X 10.6 SDK prevents boost 1.36 build
by Allen Cronce 04 Sep '08

04 Sep '08

Hi all, I have the Mac OS X 10.6 (Snow Leopard) SDK on my dev system. The presence of this SDK prevents boost 1.36 from building: --snip-- ./tools/jam/src/bin.macosxx86/bjam debug release --toolset=darwin -- architecture=combined --layout=system threading=multi address-model=32 link=shared,static macosx-version=10.4 --prefix=../1_36_0_install -- exec-prefix=../1_36_0_install install boost_1_36_0/tools/build/v2/build/feature.jam:466: in feature.validate- value-string from module feature error: "10.6" is not a known value of feature <macosx-version> error: legal values: "10.5" "10.4" "10.3" "10.2" "10.1" "iphone-2.0" "iphone-1.x" "iphonesim-2.0" boost_1_36_0/tools/build/v2/build/property.jam:276: in validate1 from module property boost_1_36_0/tools/build/v2/build/property.jam:301: in validate from module property boost_1_36_0/tools/build/v2/build/property.jam:310: in property.validate-property-sets from module property boost_1_36_0/tools/build/v2/build/toolset.jam:151: in flags from module toolset boost_1_36_0/tools/build/v2/tools/darwin.jam:227: in init-available- sdk-versions from module darwin boost_1_36_0/tools/build/v2/tools/darwin.jam:178: in darwin.init from module darwin boost_1_36_0/tools/build/v2/build/toolset.jam:38: in toolset.using from module toolset boost_1_36_0/tools/build/v2/build-system.jam:434: in process-explicit- toolset-requests from module build-system boost_1_36_0/tools/build/v2/build-system.jam:513: in load from module build-system boost_1_36_0/tools/build/v2/kernel/modules.jam:281: in import from module modules boost_1_36_0/tools/build/v2/kernel/bootstrap.jam:128: in boost-build from module boost_1_36_0/boost-build.jam:16: in module scope from module --snip-- The workaround was for me to hide the SDK, run configure again, then build. I still can't build successfully, due to an unrelated issue. But I'll post that separately in order to try and keep things clear. Snow Leopard will be here before you know it, so at some point the boost build system should be updated to know about 10.6. For that matter, maybe a new SDK would just generate a warning, not a hard error. Best, -- Allen Cronce

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library accumulator, example sum_accumulator
by Kim Kuen Tang 03 Sep '08

03 Sep '08

Hi all, i ' ve written a piece of code to get the class sum_accumulator working which is described in the user's guide http://boost-sandbox.sourceforge.net/libs/accumulators/doc/html/accumulator…. The function result must be provided with a struct dont_care. And the constructor of dont_care must be provided with a value to get an instanciation. In my opinion a default constructor taking no arguments for the struct dont_care must exists so the user can write code like dont_care(). To get the example working i must write code like sumacc.result(*dont_care(0.0)*) to get the result from my accumulator. And this is a little bit unnecessary. with regards, Kim Tang the code below is tested with visual studio 2008. #include <iostream> #include <boost/accumulators/framework/accumulator_base.hpp> #include <boost/accumulators/framework/parameters/sample.hpp> using namespace boost::accumulators; namespace boost { // Putting your accumulators in the namespace accumulators { // impl namespace has some namespace impl { // advantages. See below. template<typename Sample> struct sum_accumulator // All accumulators should inherit from : accumulator_base // accumulator_base. { typedef Sample result_type; // The type returned by result() below. template<typename Args> // The constructor takes an argument pack. sum_accumulator(Args const & args) : sum(args[sample | Sample()]) // Maybe there is an initial value in the { // argument pack. ('sample' is defined in } // sample.hpp, included above.) template<typename Args> // The accumulate function is the function void operator ()(Args const & args) // call operator, and it also accepts an { // argument pack. this->sum += args[sample]; } result_type result(dont_care) const // The result function will also be passed { // an argument pack, but we don't use it here, return this->sum; // so we use "dont_care" as the argument type. } private: Sample sum; }; }}} int main() { try { boost::accumulators::impl::sum_accumulator<double> sumacc(sample=0.0); sumacc(sample=1.2); std::cout<<sumacc.result(*dont_care(0.0)*)<<"\n"; return EXIT_SUCCESS; } catch(std::exception& e) { std::cout<<"Errors with message: "<<e.what()<<"\n"; return EXIT_FAILURE; } catch(...) { std::cout<<"Unknown Errors \n"; return EXIT_FAILURE; } }

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[Iostreams] Can't open mapped_file data file on Windows
by Allen Cronce 03 Sep '08

03 Sep '08

Hi all, I'm trying to use mapped_file from the Boost 1.35.0 Iostreams library to open a data file for reading and writing. My code works fine under Mac OS X, which is posix, of course. But under Windows (built with VS2005), I get an access error. Here's a code sample that works on Mac OS X and fails under Windows: --snip-- /** Test boost iostream mapped_file. */ static int BoostMappedFileTest(void) { int result = 0; std::cout << "\nRunning BoostMappedFileTest..." << std::endl; // Initialize our test directory fs::path testDirPath( "BoostMappedFileTest" ); create_directory(testDirPath); // Initialize a test file buffer with some data const size_t kTestFileSize = 4096; boost::scoped_array<char> fileBuffer( new char[kTestFileSize] ); char* pCur = fileBuffer.get(); char curChar = 0; for( size_t i = 0; i < kTestFileSize; ++i ) { *pCur++ = curChar++; } // Write the data to a test file. Be sure to explicitly close it. fs::path testFilePath( testDirPath / "test_mapped_file" ); boost::filesystem::ofstream testFile( testFilePath, ios::trunc | ios::binary ); testFile.write(fileBuffer.get(), kTestFileSize); testFile.close(); // Try and open the test file as a memory mapped file. string testFilePathStr = testFilePath.file_string(); mapped_file mappedFile(testFilePathStr); // We never get here under Windows with boost 1.35.0. The file fails to // open with an access error, although it throws with a more obscure error // due to a clean up bug. // Compare the mapped file data to our original buffer const char* mmConstData = mappedFile.const_data(); bool compareSucceeded = (0 == memcmp(fileBuffer.get(), mmConstData, kTestFileSize)); if (!compareSucceeded) { throw runtime_error("The boost memory mapped file data doesn't match our buffer!"); } return result; } --snip-- The problem seems to come from passing GENERIC_ALL as the "dwDesiredAccess" parameter to the CreateFileA call. If I change the implementation to pass GENERIC_READ | GENERIC_WRITE, then it works in my test scenario. Please note that I haven't tried pointing the current code at an actual executable to see if it works with GENERIC_ALL. If you assume a strict interpretation of the mapped_file API, the mode of BOOST_IOS::in would map to GENERIC_READ in the Windows world, and BOOST_IOS::out would map to GENERIC_WRITE. There is no corresponding "execute" flag that I can see in this API. Since I'm only interested in mapping data files, I could certainly modify the boost 1.35.0 sources so that only GENERIC_READ and GENERIC_WRITE are passed to the Windows API depending on what BOOST_IOS mode was specified. But I'm not sure of what dependancies may exist between the mapped_file implementation and other boost libraries. The interprocess library, for example, hasn't yet fallen under my sphere of research ;-) Could someone please advise me as to the best course of action that will allow me to open memory mapped data files on Windows without adversely impacting the rest of the boost libraries? BTW, there's a secondary problem where if an error happens at CreateFileA, the clean up code fails and throws an invalid handle exception. This is because the mapped_handle_ member variable is initialized to NULL instead of INVALID_HANDLE_VALUE (which is what the clean up test is looking for). After code inspection of the svn trunk, I *think* this secondary issue has already been resolved. However, the latest sources look like they're still using GENERIC_ALL as the access parameter to the CreateFile, so my reported problem is still relevant and needs to be resolved. Thanks in advance for any suggestions. Best, -- Allen Cronce

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Bitset issue
by Sean Farrow 03 Sep '08

03 Sep '08

Hi: I am using a bitset to store up to 63 different values as a key in a mapp This does appear to be working though, as I carn't seem to get an iterator to accept any bitset even though it is defined, has any one go any othe ideas as to how I could tackle this issue. Regards Sean. __________ Information from ESET NOD32 Antivirus, version of virus signature database 3390 (20080826) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com

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[boost.asio] string iterator not dereferencable using message in async_send_to
by John Urberg 03 Sep '08

03 Sep '08

I'm using async_send_to to send multicast messages. When I try to send data in a std::string, I always get a 'string iterator not dereferencable' assertion failure. I'm using boost 1.35 and VC9. Here's the code: // instance variable string buffer; // code in method buffer = BuildHailMessage(); socket.async_send_to( boost::asio::buffer(buffer), endpoint, boost::bind( &MulticastServer::HandleSendTo, this, boost::asio::placeholders::error)); I've also tried using char* buffer, dynamically allocating it based on the message length and then use std::copy to copy the std::string into the buffer, but I get heap corruption assertions when trying to delete [] it. The only way I've gotten this to work is using a fixed char[] buffer. Is there a way I can use a std::string with async_send_to? Do I need to use a different type of asio::buffer class? Thanks, John

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transform_view: question about boilerplate code
by Zeljko Vrba 02 Sep '08

02 Sep '08

I have succeeded in writing the following transform functor: typedef bf::map<bf::pair<net, unsigned>, bf::pair<pin, unsigned> > Map; typedef bf::vector<unsigned, unsigned> Pair; struct Map2Pair { template<typename Sig> struct result; template<typename U> struct result<Map2Pair(U)> : remove_reference<T::second_type> { }; template<typename T> typename T::second_type operator()(T t) const { return t.second; } }; I have tested it, it works. The result magic has been copied from the transform_view example in the documentation and adjusted for the proper return type. Where can I read a bit more about result conventions? In particular, how does the template<typename U> struct result<Map2Pair(U)> : remove_reference<T::second_type> { }; specialization work when Map2Pair is a struct, and it doesn't even have a constructor! Even worse, why does it work at all when T is not in the scope of the template (.. because it's never used?) Yes, it is not used, the following functor also works: struct Map2Pair { template<typename T> typename T::second_type operator()(T t) const { return t.second; } }; When and how is the above version preferred than the simpler version?

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[Boost.Asio] service_name/port inconsistency
by Vjekoslav Brajkovic 02 Sep '08

02 Sep '08

Hi. When designing server-client model, one has to use boost::asio::ip::tcp::endpoint and boost::asio::ip::tcp::resolver::query respectively. What I am confused about is that query accepts std::string& service as a parameter whereas endpoint only accepts unsigned short. When writing code, it is really easy to get confused which constructor takes string and which short. I would appreciate is somebody could tell me if there is a way to create a server side component using integer as a service. - V

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