January 2010 - Boost - lists.preview.boost.org

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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[Serialization] memory leak when serialising a map containing shared_ptrs
by richard bradley 28 Jan '10

28 Jan '10

I'm finding that Boost.Serialization is leaking memory when deserialising std::map<string,boost::shared_ptr<X>>. Maybe this is a sign that my data structures are too complicated? ;-) This wouldn't bother me that much, except that I'm also using Boost.Test, which gives lots of angry messages about leaked memory at the end of my tests (I'm using MSCRT). I've attached a simple test case which demonstrates this. Can anyone shed some light on what's going on here? Have I used any of the libraries incorrectly? Is there anything I can do to fix this? I'm using Visual Studio 2008, and boost 1.41.0 The output from the attached test looks like: =========== Running 1 test case... MyClass @3532504 with 1 children MyClass @3532960 with 1 children Detected memory leaks! Dumping objects -> {800} normal block at 0x0035EDE8, 1 bytes long. Data: < > CD Object dump complete. =========== I've also attached a stack trace which I got by breaking on the non-free'd memory allocation,using "--detect_memory_leak=800" Thanks very much, Rich

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unzip .zip file and browse to compressed files
by Andrej van der Zee 28 Jan '10

28 Jan '10

Hi, I am looking for a way to uncompress a zip-file (which contains multiple files/dirs) and browse through the contents. Does boost provide support for the first part? I looked at iostreams with a zlib uncompressor, but as far as I can see it assumes a single zipped file. Thank you, Andrej

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