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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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doc for is_lvalue_iterator?
by Neal Becker 29 Jan '10

29 Jan '10

I don't see any doc for is_lvalue_iterator (and related metafunctions)

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type of iterator_facade::value_type
by Neal Becker 29 Jan '10

29 Jan '10

According to iterator_facade doc: typedef remove_const<Value>::type value_type; Why remove_const? This makes it hard to detect if the resulting iterator points to a const value. In order to further adapt such an iterator, I needed to use the reference type instead of the value type to detect constness: typename boost::is_const< typename boost::remove_reference< typename std::iterator_traits<BaseIterator>::reference >::type >::type,

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Review Request: Creasing (Sequence Properties)
by Grant Erickson 28 Jan '10

28 Jan '10

The creasing algorithm templates define four template functions for determining the order properties of sequences, specifically: * Increasing * Decreasing * Strictly Increasing * Strictly Decreasing The implementation is a fairly trivial composition of the STL adjacent_find, not2 and {greater,less,greater_equal,less_equal}. For the purposes of sequence ordering validation, using these templates is more efficient and straightforward than creating a temporary, sorted version of some sequence and comparing it against the original sequence. Example: bool CheckPoints(const Points & inPoints) { const bool strictlyIncreasing = is_strictly_increasing(inPoints.begin(), inPoints.end()); if (!strictlyIncreasing) { cerr << "Points must be in increasing order with " "no duplicate values." << endl; } return strictlyIncreasing; } The review files are available in both Sandbox and Vault: Sandbox: boost/algorithm/creasing.hpp libs/algorithm/creasing/example/creasing_ex.cpp libs/algorithm/creasing/example/Jamfile libs/algorithm/creasing/test/creasing_test.cpp libs/algorithm/creasing/test/Jamfile.v2 Vault: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=creasin g.zip&directory=Algorithms Regards, Grant Erickson

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[Boost.Thread]
by Andrew Chinkoff 28 Jan '10

28 Jan '10

Hi. There is a test program I would to be explained to me: *** BEGIN OF TEST PROGRAM *** #include <stdio.h> #include <boost/thread.hpp> #define USE_SPINLOCKS //#define USE_MUTEXES boost::thread th1; boost::thread th2; boost::mutex mutex; int global_int = 0; bool IsNotEven(int code) { boost::mutex::scoped_lock locker(mutex); bool ret = (code & 1); return ret; } void thread_func() { for(int i = 0; i < 1000000; ++i) { #ifdef USE_MUTEXES if(IsNotEven(global_int)) // (1) #elif defined USE_SPINLOCKS if(__sync_fetch_and_and(&global_int, 1)) // (2) #else ERROR__WRONG_COMPILED; #endif global_int+=9; else global_int+=1; } } int main() { th1 = boost::thread(&thread_func); th2 = boost::thread(&thread_func); th1.join(); th2.join(); printf("global_int = %d\n", global_int); return 0; } *** END OF TEST PROGRAM *** Results of test program: 1) Test program compiled with USE_SPINLOCKS. Outputs are always: "global_int = 10" "global_int = 10" "global_int = 10" 2) Test program compiled with USE_MUTEXES. Outputs differ from each other: "global_int = 10000008" "global_int = 10000000" "global_int = 9763210" Could you explain me why outputs produced with USE_SPINLOCKS compilation differ from USE_MUTEXES ones? And what is the difference between (1) and (2) lines? Best, Andrew. P.S.: I use guest Ubuntu-8.04 installed on VirtualBox. Host OS = Vista.

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detecting a constructor with a specific signature
by Kenny Riddile 28 Jan '10

28 Jan '10

I'm trying to create a type trait to detect the presence of a constructor with a very specific signature. Types passed to this trait will *always* have a constructor of the form: T( const std::string& ); but some of them will have this constructor as well: T( const std::string&, Foo& ); // Second parameter will always be a Foo& I would like to create a type trait that returns true when the second constructor is present. I can't simply do: !is_convertible<std::string, T>::value since that will return false when the second constructor is present since all Ts are convertible from std::string. Is it possible to create such a trait?

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Trunk testing broken (Python and Utility)
by K. Noel Belcourt 28 Jan '10

28 Jan '10

Hi, There's at least two separate problems in trunk. Missing files in the Python library. error: Unable to find file or target named error: 'union.cpp' error: referred from project at error: '../libs/python/test' Missing files in the Utility library, error: Unable to find file or target named error: 'noncopyable_adl_barrier.cpp' error: referred from project at error: '../libs/utility/test' -- Noel

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Range-aware version of min and max
by Zachary Turner 28 Jan '10

28 Jan '10

I am often frustrated by the inability of std::min and std::max to deal with data types of different ranges. For example: boost::uint64_t big = 9876543210ULL; boost::uint32_t small = 12345; boost::uint32_t smallest = std::min(big, small); will generate a compiler warning about possible loss of data due to converting from boost::uint64_t to boost::uint32_t. Obviously such a scenario is impossible since by definition the result can be no larger than the maximum value of a uint32. Previously there was a discussion on the list about adding operators such as is_addable, is_multipliable, is_less_comparable, etc. Using such a class, one could re-write min and max as follows (I'm sure someone will come up with a problem with this, or a better implementation, but anyway the idea should be clear): namespace boost { template<class A, class B> struct min_result { typedef mpl::if_c<(integer_traits<A>::const_max < integer_traits<B>::const_max), A, B>::type type; }; template<class A, class B> struct max_result { typedef mpl::if_c<(integer_traits<A>::const_min > integer_traits<B>::const_min), A, B>::type type; }; template<class A, class B> min_result<A,B>::type min(const A& a, const B& b) { return static_cast<min_result<A,B>::type>((a < b) ? a : b); } template<class A, class B> max_result<A,B>::type max(const A& a, const B& b) { return static_cast<max_result<A,B>::type>((a > b) ? a : b); } I'm sure there's some implementation details I haven't considered, but is there any fundamental reason why an approach like this would be flawed or undesirable? Zach

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Please stay on-topic (was: C++ and quality of software)
by David Abrahams 28 Jan '10

28 Jan '10

This discussion is really not relevant to Boost, is it? At Mon, 25 Jan 2010 14:28:34 -0800, Peter Foelsche wrote: > > > "Marshall Clow" <mclow.lists(a)gmail.com> wrote in message > news:D43C711F-03E0-4A3C-BE40-BA99BE379F30@gmail.com... > > > Exceptions > > ▶ We do not use C++ exceptions. > > > > Run-Time Type Information (RTTI) > > ▶ We do not use Run Time Type Information (RTTI). > > > I think this is an embarrasement for google. > Didn't they claim to hire only very good people? > I would not want to work under these conditions. > > If there is again some security hole due to a buffer overflow, > such an institution could claim, that software using fixed-sized-buffers > would not get their stamp of approval. > And that the customer should be looking and asking for this stamp of > approval when buying software. > > How many fixed sized buffers are in the main OSs? -- Dave Abrahams Meet me at BoostCon: http://www.boostcon.com BoostPro Computing http://www.boostpro.com

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