January 2010 - Boost - lists.boost.org

[transaction] New Boost.Transaction library under discussion
by vicente.botet 02 Feb '10

02 Feb '10

Hi Stefan, Bob, I've created in the sandbox the transaction directory (http://svn.boost.org/svn/boost/sandbox/transaction/) so we can share our work. I've created also a wiki page (http://svn.boost.org/trac/boost/wiki/BoostTransaction) on which we can compile the result of our discussions, requirements for the library, design, ... If you don't have right access to the Boost wiki pages, please request them throught this ML. Of course, anyone is welcome to participate, or comment on this wiki. HTH, _____________________ Vicente Juan Botet Escribá

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[thread] why crash launching a thread?
by David M. Cotter 01 Feb '10

01 Feb '10

i'm launching a new thread from an existing background thread, BUT it is crashing. i don't know if it happens often yet, but was wondering what could possibly cause this? Thread 10 Crashed: 0 libSystem.B.dylib 0x96ce435d usleep$NOCANCEL$UNIX2003 + 0 1 libSystem.B.dylib 0x96d05a50 abort + 105 2 libstdc++.6.dylib 0x96bb2fda __gnu_cxx::__verbose_terminate_handler() + 433 3 libstdc++.6.dylib 0x96bb117a __cxxabiv1::__terminate(void (*)()) + 10 4 libstdc++.6.dylib 0x96bb11ba __cxxabiv1::__unexpected(void (*)()) + 0 5 libstdc++.6.dylib 0x96bb12b8 __gxx_exception_cleanup(_Unwind_Reason_Code, _Unwind_Exception*) + 0 6 libboost_thread.dylib 0x006af933 boost::thread::start_thread() + 195 7 com.kjams.kjams 0x001281d1 CThreads::Fork(APP_ThreadType, long (*)(void*, long), long (*)(void*, long), void*, char const*) + 1521 8 com.kjams.kjams 0x0012858b CT_Preemptive::call(char const*) + 91 9 com.kjams.kjams 0x00139fc2 CSpooler::Fork_Spool(CSpooler*, bool) + 290 10 com.kjams.kjams 0x0027fd05 CSongImporter::EncodeSong(CSI_PersistantQueData*, CSpooler*) + 1109

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[log] Release Candidate 4 released
by Andrey Semashev 01 Feb '10

01 Feb '10

I'm proud to announce that I've released the fourth candidate of Boost.Log for the review. There were many improvements since the passed year of development. Many of them reflect the discussion of RC3. Here's a short list of major changes: * Substantial documentation improvement. The tutorial section has been reorganized. * Removed rotating file stream. As a replacement, a new file sink has been added, which allows to achieve the same results ans adds a few more features. It is now possible to collect rotated log files in a dedicated directory. * Added a new multifile sink backend. * Added a new ordering asynchronous sink frontend. * The syslog sink backend is now supported on Windows, too. The sink no longer requires native support for POSIX API for syslog, but is able to send syslog packets to a remote server over UDP. * Added support for scoped logging. There is now a distinct log record entity, which is returned by the core as a result of filtring. * Added support for exception control. * Added a new mode of logging, called trivial logging. The more complete change log is available here: http://tinyurl.com/ybcghuf The library with docs, tests and examples has been updated in Boost.Vault: http://tinyurl.com/cm9lum There's SVN repository available on SourceForge project page: http://tinyurl.com/ye23wyh The docs are also available online here: http://tinyurl.com/5e4fd7 Comments are welcome.

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Boost.Atomic request for review/inclusion
by Helge Bahmann 01 Feb '10

01 Feb '10

Hello, First of all I would like to thank for the comments that I have received so far, I have incorporated almost all of them I think. Boost.Atomic is now in a form that I consider calling it a release. It has support for "true" atomic variables on: - gcc/x86, 32-bit (tested on Linux, FreeBSD) - gcc/x86, 64-bit (tested on Linux) - gcc/powerpc32 (tested on Linux, Mac OS X) - gcc/powerpc64 (untested) - generic Win32 (tested with Visual Studio Express on Win XP) For all others it falls back gracefully to locked operation. There is proper quickbook documentation, including a hopefully illustrative example section. If you have an unsupported platform, contact me and I will attempt to provide support for it (usually it is just a matter of testing). Otherwise I would like to request considering the library for inclusion and appreciate any further comments. Everything available as usual at: http://www.chaoticmind.net/~hcb/projects/boost.atomic Best regards Helge

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[Serialization] virtual function and virtual inheritance
by fab 31 Jan '10

31 Jan '10

Hi, I have a compilation error with a virtual function inside a virtual base class. For example, I just add a function f() inside the unit test : "test_diamond.cpp". class base { ... virtual void f() =0; ... }; class derived1 { ... virtual void f(){} ... }; gcc 4.3, returns me an error: error: no unique final overrider for `virtual void base::f()' in `boost::detail::is_virtual_base_of_impl<derived1, final, mpl_::bool_< true> >::X' The same code works properly with msvc 2005. Best regards, Fabien Castan

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RFC: Sequence Properties and Boost Algorithm/Functional
by Grant Erickson 31 Jan '10

31 Jan '10

For a recent project, I needed to inquire about a sequence of objects and make a determination as to whether the sequences were: * Increasing * Strictly Increasing * Decreasing * Strictly Decreasing Looking through STL, Boost documentation, Boost sources and headers and the Boost mailing lists I was able to find neither an existing algorithm or stateful unary predicate functor for accomplishing this for a pair of input iterators. However, I was a bit surprised considering that this seems like a sequence property query that would tend to come up fairly often and serve a general utility. Did I just fail to form the proper search/query or am I overestimating the general utility? Regardless, I forged ahead with the rather naïve implementation (see below), which can be used as a predicate with for_each as shown: const int strictlyIncreasingValues[] = { 1, 2, 3, 4, 5 }; bool isStrictlyIncreasing; isStrictlyIncreasing = std::for_each(strictlyIncreasingValues, strictlyIncreasingValues + 5, is_strictly_increasing<int>()); assert(inStrictlyIncreasing == true); However, acknowledging the inefficient and naïveté of the first implementation, this is probably more algorithm than functional in that for_each with a stateful predicate is wasteful in walking the entire sequence (i.e. if any arbitrary subsequence fails to meet the property predicate criteria, the whole sequence fails). Is a smarter realization of this as an algorithm a potential candidate for boost::algorithm? Naïve, inefficient functional implementation to be used with for_each: #include <functional> #include <boost/function.hpp> template <typename T> struct creasing : public unary_function<T, bool> { protected: typedef unary_function<T, bool> base_type; typedef typename base_type::argument_type argument_type; typedef typename base_type::result_type result_type; typedef boost::function<result_type (const argument_type &a, const argument_type &b)> binary_predicate; creasing(const binary_predicate & inPredicate) : base_type(), mPredicate(inPredicate), mCreasing(true), mInited(false), mLast() { return; } public: result_type operator()(const argument_type & x) { if (mCreasing) { if (mInited) { mCreasing = mPredicate(mLast, x); } else { mCreasing = true; mInited = true; } mLast = x; } return (mCreasing); } operator result_type() const { return (mCreasing); } private: const binary_predicate mPredicate; result_type mCreasing; result_type mInited; argument_type mLast; }; template <typename T> struct is_increasing : public creasing<T> { typedef creasing<T> base_type; typedef typename base_type::argument_type argument_type; is_increasing(void) : base_type(std::less_equal<argument_type>()) {} }; template <typename T> struct is_decreasing : public creasing<T> { typedef creasing<T> base_type; typedef typename base_type::argument_type argument_type; is_decreasing(void) : base_type(std::greater_equal<argument_type>()) {} }; template <typename T> struct is_strictly_increasing : public creasing<T> { typedef creasing<T> base_type; typedef typename base_type::argument_type argument_type; is_strictly_increasing(void) : base_type(std::less<argument_type>()) {} }; template <typename T> struct is_strictly_decreasing : public creasing<T> { typedef creasing<T> base_type; typedef typename base_type::argument_type argument_type; is_strictly_decreasing(void) : base_type(std::greater<argument_type>()) {} }; Regards, Grant

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[atomic] Availability detection
by Andrey Semashev 31 Jan '10

31 Jan '10

Hi, Will there be a way to detect if specific operations over a specific type are available atomically on the current platform? That is, if I know that atomic operations are emulated with locks, I want to fall back to another branch of my code with explicit locks, rather than the emulated atomics.

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codepad code longevity ?
by Joel de Guzman 31 Jan '10

31 Jan '10

Hi, We see more and more people post code using Codepad. Is that good? In the Spirit list, we've had this discussion about longevity of code posted to Codepad: http://article.gmane.org/gmane.comp.parsers.spirit.general/18220 I can't see any information regarding policy on how code is retained. Is there? I've heard they say the post is valid for 24 hours. If that's the case, then we should ban the use of codepad. People here, myself included, need pasted code to be permanent for future reference. Thoughts? Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net http://www.facebook.com/djowel Meet me at BoostCon http://www.boostcon.com/home http://www.facebook.com/boostcon

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[circular_buffer] Serialization support for circular_buffer
by Brian Wood 31 Jan '10

31 Jan '10

B"H Shalom, Boost, The C++ Middleware Writer now supports marshalling circular_buffers. This is done by transmitting a circular buffer's capacity, then size, followed by it's elements. An example of the code used when marshalling a circular_buffer is here -- http://webEbenezer.net/posts/cirbuf.hh. -- Brian Wood http://www.webEbenezer.net (651) 251-9384

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[asio] [function] Strange corruption error with boost::function and asio
by Zachary Turner 29 Jan '10

29 Jan '10

I'm not sure if I'm experiencing a bug in boost, bug in compiler (VS 9.0 service pack 1), or bug somewhere else, but I'm having trouble reading boost::function code enough to be able to figure out. A little background: I'm using boost::asio to read from a disk, and then boost::asio to write results to a socket. Everything works completely fine most of the time, but in some cases there's an error on my server (which is largely irrelevant here as it's not even written in C++) and the server crashes unexpectedly. I suspect the error is occuring while I'm in the middle of an asynchronous network write, because the very first odd behavior surfaces in my network write completion routine. I can go into more detail about how I'm using boost::function and boost::asio in conjunction if necessary, but for now I'll just post the bare minimum needed to be able to make any sense at all of what I'm doing (which is still alot, my apologies for the length). Anyway: - my completion routine has the following signature: void async_service_write_network::write_data_handler(asio_handler wrapped_handler, boost::system::error_code error, size_t bytes_transferred) - asio_handler (referenced in the previous signature) is defined as follows: typedef boost::function<void (boost::system::error_code, size_t)> asio_handler; Which is exactly the same but contains a wrapped handler at the front so I can privately intercept the handler at various points along the chain, and then have the private handler do arbitrary work then invoke the wrapped handler. I do this with boost::bind as follows asio_handler wrapped_handler = boost::bind( &async_service_write_network::write_data_handler, this, handler, _1, _2); socket_.async_send( buffer, boost::bind( wrapped_handler, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); To explain the odd behavior, I've put a breakpoint in write_data_handler. Quick version if you don't feel like reading, the function arguments seem to be being corrupted either by boost::bind or boost::function. Long version, looking at the values of the arguments shows the following: error {m_val=23843184 m_cat=0x000000000000305d } boost::system::error_code m_val 23843184 int m_cat 0x000000000000305d const boost::system::error_category * boost::noncopyable_::noncopyable {...} boost::noncopyable_::noncopyable __vfptr CXX0030: Error: expression cannot be evaluated So I move one level up the callstack. This puts me in: template<class R, class T, class A1, class A2, class A3 BOOST_MEM_FN_CLASS_F> class BOOST_MEM_FN_NAME(mf3) { //Boost 1.39 mem_fn_template.hpp line 384 R operator()(T * p, A1 a1, A2 a2, A3 a3) const { BOOST_MEM_FN_RETURN (p->*f_)(a1, a2, a3); } } Examining a1, a2, and a3 shows that they are what they appear to be. Walking one more level up the callstack and this is no longer the case: template< class A1, class A2, class A3, class A4 > class list4: private storage4< A1, A2, A3, A4 > { //Bind.hpp line 450 template<class F, class A> void operator()(type<void>, F & f, A & a, int) { unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_], a[base_type::a3_], a[base_type::a4_]); } } Examining the contents of 'a', I see this: - a {...} boost::_bi::list2<boost::system::error_code &,unsigned __int64 &> & - boost::_bi::storage2<boost::system::error_code &,unsigned __int64 &> {a2_=12381 } boost::_bi::storage2<boost::system::error_code &,unsigned __int64 &> - boost::_bi::storage1<boost::system::error_code &> {a1_={...} } boost::_bi::storage1<boost::system::error_code &> - a1_ {m_val=0 m_cat=0x000000014000ac48 } boost::system::error_code & m_val 0 int + m_cat 0x000000014000ac48 system_category_const const boost::system::error_category * a2_ 12381 unsigned __int64 & Somehow this error code is becoming corrupted. It is clearly has an m_val of 0 here, and an m_cat of 0x14000ac48 here, and in the very next function on the call stack, it has an m_val of 23843184, and an m_cat of 0x305d. Am I missing something obvious or is there an actual boost/compiler bug going on here?

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