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Re: [boost] [asio] failure in ~wrapped_handler
by Dean Michael C. Berris 27 Jun '08

27 Jun '08

Of course I should have attached the trace... ;) -- Dean Michael Berris Software Engineer, Friendster, Inc. > -----Original Message----- > From: Dean Michael C. Berris > Sent: Friday, June 27, 2008 5:40 PM > To: 'boost(a)lists.boost.org' > Subject: [asio] failure in ~wrapped_handler > > Hi everyone, > > I recently ran into a problem with Boost.Asio while using a > slightly modified version of the HTTP 2 example server. The > debugger trace (attached) shows where a segfault had occurred > in the code. > > The short of it is that when ~wrapped_handler is called, the > call to boost::detail::atomic_exchange_and_add fails when > boost::detail::sp_counted_base::release is invoked. It occurs > when a handler_wrapper is deleted/destructed > (~handler_wrapper is called) in the strand_service. > > I'm just wondering what could be causing this -- it's worth > noting that under not-so-heavy load, the problem does not > manifest itself; but soon enough when the load on the server > goes up (more incoming connections) the server crashes consistently. > > Any pointers where I should be looking? I'm using Boost.Trunk > revision number 43296. > > -- > Dean Michael Berris > Software Engineer, Friendster, Inc.

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[thread] Backwards compatibility for timed_lock?
by Chris Newbold 26 Jun '08

26 Jun '08

We're in the process of upgrading to 1.35 and have discovered that there are no timed_lock() overloads accepting the old xtime structure. Was this intentional or an oversight? It isn't mentioned in the list of "breaking changes" in the 1.35 release notes. For example, timed_wait() does have overloads for xtime... -Chris

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[type traits] possible bug in boost::is_convertible for types with private copy constructors
by Daniel James 26 Jun '08

26 Jun '08

>From the move semantics thread: 2008/6/24 David Abrahams <dave(a)boostpro.com>: > Daniel James wrote: >> It mostly works. I've found two problems so far. Firstly, >> is_convertible didn't work for the type, > > You found a bug in is_convertible? I don't know if it's a bug. The example below fails to compile. #include <boost/type_traits/is_convertible.hpp> template <typename T> struct move_from {}; class Y { Y(Y& rhs); public: Y(move_from<Y>) {} }; bool const r = boost::is_convertible<move_from<Y>, Y>::value;

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[graph] multiplicative spanner code
by Dimitrios Michail 26 Jun '08

26 Jun '08

Hi, I have written a small piece of code which computes a 2k-1 multiplicative spanner (k is an integer parameter) of undirected weighted graphs. This spanner is simply a subgraph of an input graph which preserves shortest path distances up to a 2k-1 factor, that is the shortest path from u to v in the spanner is at most 2k-1 times the shortest path from u to v in the original graph. The main benefit is that there is always a 2k-1 spanner with O(n^{1+1/k}) edges. The algorithm is due to Althoefer, Das, Dobkin, Joseph and Soares. It is a simple generalization of Kruskal's algorithm (thus I used Kruskal's algorithm as a template). While not the fastest possible, it is simple and elegant. Is there any place where I could upload my code for interested people to review and comment? Best, Dimitris

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Deprecate BOOST_STATIC_ASSERT?
by David Abrahams 26 Jun '08

26 Jun '08

Yesterday someone on the user's list posted a message (http://article.gmane.org/gmane.comp.lib.boost.user/36884) about a "compilation error in the boost code:" s-test.h:49: instantiated from here /usr/include/boost/archive/detail/oserializer.hpp:567: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>' make: *** [stest] Error 1 and proceeded to try to analyze the BOOST_STATIC_ASSERT implementation to see what was wrong with it. Granted, most people figure out what a static assertion is supposed to be, but still, the error message gave no clue about what might have gone wrong... no clue to the user, and no clue to anyone reading his posting, unless they were going to look up the line in the source file... oops, I take it back. My copy of oserializer.hpp doesn't even have a line 567, and the posting doesn't indicate which version the user has. For several releases now we've had a suite of static assertion tools that give far superior error messages to what BOOST_STATIC_ASSERT can provide (http://www.boost.org/doc/libs/1_35_0/libs/mpl/doc/refmanual/asserts.html) I think <radical-idea>it's time to deprecate BOOST_STATIC_ASSERT</radical-idea> or at *least* put a prominent note in its documentation directing people at the BOOST_MPL_ASSERT macros. Thoughts? -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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function based associative generator
by Dean Michael Berris 26 Jun '08

26 Jun '08

Hi Everyone, I've recently been playing around with a relatively simple idea: creating a generic associative generator. For some background, here's a simple problem (which is quite common in mathematics): I want to be able to pull out the nth fibonacci number in the fibonacci sequence. To do this, the traditional implementation in C++ would be to create a function that yields the nth fibonacci number. This seems fine, because as C++ programmers we would be used to the notion of using functions. However, the traditional notion of a sequence in mathematics is a collection of values that can be indexed by a subscript. Consider: struct fibonacci { int operator () (int n) const { // ... }; }; boost::generator<int, int> const & fib = boost::generator<int, int>(fibonacci()); std::cout << fib[1] << std::endl; // prints 1st fibonacci number std::cout << fib[2] << std::endl; // prints 2nd fibonacci number ... Now consider that you want to deal with the generator using an STL algorithm: std::copy(fib.begin(), fib.end(), ostream_iterator<int>(std::cout, " ")); // prints the infinite sequence The iterator implementation requires that the InputType (in this case, the second 'int' template parameter to the generator) be default constructable and has a defined prefix and/or postfix increment operator. The iterator models an InputIterator. Given this, I've attached the implementation which I'm opening up for comments. If there is interest in this utility, I'm willing to write documentation and submit it for a formal review. The basic idea for this utility is to map a non-void unary function to a generator interface that provides an associative index operator (operator[]) which passes the sole argument as the argument to the wrapped function. This utility requires only the Boost.Function library, and has been tested with MSVC 2008 Express Edition. Have a good one, and I hope this helps! -- Dean Michael C. Berris Software Engineer, Friendster, Inc.

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[move semantics] Containers supporting movable-only types
by Ion Gaztañaga 26 Jun '08

26 Jun '08

Hi to all, I committed to trunk some days ago (and I plan to merge them to the release branch) some changes in Interprocess containers so that they can take advantage of C++0x rvalue references of gcc 4.3. The goal is that anyone experimenting with compilers with rvalue references (gcc 4.3 for now) can take advantage of containers that can hold movable-only types. Most of these containers (list, map/set/multimap/multiset, slist) are based on Intrusive containers. Vector and deque have more code and a move-aware vector is specially useful to achieve efficient associative ordered vectors like flat_map/flat_set/flat_multimap/flat_multiset. Current move-emulation is still based on Interprocess' own types. For Boost 1.37 I would like to change move emulation to a general Boost.Move library (if that library is ready). With new containers (forward_list) in the standard and having move-aware containers in Interprocess, I was wondering if it would be a good idea to move those containers outside Interprocess. In the future we could make those containers compatible with Scoped Allocators (2554, http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2554.pdf) Opinions? Regards, Ion

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Possible library submissions: fuzzy logic library, new container
by Alex Shafir 25 Jun '08

25 Jun '08

#include "TestModel.h" using namespace Fuzzy; // test model definition TestModel::TestModel(string file): Model(file), angle(-1), velocity(-1), speed(-1) { // fuzzy variables definitions created by the base class (Fuzzy::Model) // Input/Output methods; Input/Output arguments are refs // to double scalar variables Var& Angle = Input(angle); Var& Vlcty = Input(velocity); Var& Speed = Output(speed); // membership functions definitions created by fuzzy variables // Term method; Term method takes curve name as an argument; // cureve names are defined in the Fuzzy::Model curve definition // file MemFun& AngleNegHigh = Angle.Term("AngleNegHigh"); MemFun& AngleNegLow = Angle.Term("AngleNegLow"); MemFun& AngleZero = Angle.Term("AngleZero"); MemFun& AnglePosLow = Angle.Term("AnglePosLow"); MemFun& AnglePosHigh = Angle.Term("AnglePosHigh"); MemFun& VlctyNegHigh = Vlcty.Term("VelocityNegHigh"); MemFun& VlctyNegLow = Vlcty.Term("VelocityNegLow"); MemFun& VlctyZero = Vlcty.Term("VelocityZero"); MemFun& VlctyPosLow = Vlcty.Term("VelocityPosLow"); MemFun& VlctyPosHigh = Vlcty.Term("VelocityPosHigh"); MemFun& SpeedNegHigh = Speed.Term("AngleNegHigh"); MemFun& SpeedNegLow = Speed.Term("AngleNegLow"); MemFun& SpeedZero = Speed.Term("AngleZero"); MemFun& SpeedPosLow = Speed.Term("AnglePosLow"); MemFun& SpeedPosHigh = Speed.Term("AnglePosHigh"); // these are the model rules; syntax is pretty strightforward; // rules look like operator >> where lhs is the condition and // rhs is the conclusion; // lhs and rhs have to be in parens if they contain more then // one term because of the c++ operators precedence rules; // conclusion may be a comma separated list of output terms // in parens ((AngleZero and VlctyZero)or(AnglePosLow and VlctyNegLow)or(AngleNegLow and VlctyPosLow)) >> SpeedZero; ((AngleZero and VlctyNegLow)or(AngleNegLow and VlctyZero)) >> SpeedNegLow; ((AnglePosLow and VlctyZero)or(AngleZero and VlctyPosLow)) >> SpeedPosLow; ((AngleZero and VlctyNegHigh)or(AngleNegHigh and VlctyZero)) >> SpeedNegHigh; ((AnglePosHigh and VlctyZero)or(AngleZero and VlctyPosHigh)) >> SpeedPosHigh; } TestModel::~TestModel() { } void TestModel::run(double a, double v, double &s) { // we assign scalar variables to class members angle = a; velocity = v; speed = s; // then run the model // it should be pretty fast as it all designed to preallocate // all the needed large objects in the model constructor Model::run(); // and assign the values of output variables s = speed; }

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[1.35.0] msvc 2008 program options dynamic linking problem
by Michael Marcin 25 Jun '08

25 Jun '08

While using boost 1.35 with msvc 2008 and dynamic linking I'm getting error LNK2001: unresolved external symbol "public: static unsigned int const boost::program_options::options_description::m_default_line_length" (?m_default_line_length@options_description@program_options@boost@@2IB) error LNK2001: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > boost::program_options::arg" (?arg@program_options@boost@@3V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) While compiling: namespace po = boost::program_options; const char* configFilename = "demo.cfg"; std::string serverAddress; unsigned short serverPort; po::options_description configFile( "Configuration File Options" ); configFile.add_options() ("server-address", po::value(&serverAddress), "ip address of the server") ("server-port", po::value(&serverPort), "the server listening port") ; std::ifstream stream( configFilename ); po::variables_map vm; po::store(po::parse_config_file(stream, configFile), vm); po::notify( vm ); Is this a bug or a build problem? Thanks, Michael Marcin

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[iostreams] Patch for mapped_file.cpp.
by Jurko Gospodnetić 25 Jun '08

25 Jun '08

Hi. I'm attaching a patch for libs/iostreams/src/mapped_file.cpp which corrects the mapped_file_source::operator!() operator. It seems to have been erroneously returning true in case the implementation object exists but has its error_ flag set. Hope this helps. Best regards, Jurko Gospodnetić Index: libs/iostreams/src/mapped_file.cpp =================================================================== --- libs/iostreams/src/mapped_file.cpp (revision 46155) +++ libs/iostreams/src/mapped_file.cpp (working copy) @@ -150,7 +150,7 @@ } bool mapped_file_source::operator!() const -{ return !!pimpl_ || pimpl_->error_; } +{ return !pimpl_ || pimpl_->error_; } BOOST_IOS::openmode mapped_file_source::mode() const { return pimpl_->mode_; }

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