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boost::filesystem::filesystem_error returns wrong error code on bad path?
by Ed Johnson 25 May '06

25 May '06

Hi, When I create a bad path on purpose, the error code that boost returns is: 2 other_error, // library generated error However, the exception.hpp what() returns the string: boost::filesystem::path: invalid name "testwrite1::.txt" in path: "../data/TestFileIO/testwrite1::.txt" It seems like the string from what() correctly identifies the error at a bad path name, but it is not correctly translated in the error code enumeration. I thought it should be: 6 path_error Using boost 1.33.1 http://www.boost.org/libs/filesystem/doc/exception.htm Any thoughts? Thanks, Ed Johnson

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Google Summer of Code -- 10 Projects Assigned!
by Jeff Garland 25 May '06

25 May '06

Hi All - Just a quick note to let everyone know that Boost has been assigned 10 SOC projects! This is more than we expected and I'm hopeful will result in some great work. Even so, there are many excellent students and projects that applied for Boost projects and were NOT selected. The competition for these 10 slots was quite brutal. The choices were extremely difficult to make. It was often very hard to decide between a totally novel, high risk, project proposal and a fairly straight-forward extension to a current library. As you'll see, we ended up with some of both. The mentors have been trying to reach everyone with a notification one way or another, but it's a large list. All applicants should have heard from Google by now. If you have questions you can post to boost_soc2006(a)crystalclearsoftware.com and someone should get back to you. I'm not going to publicy share the details of the list just yet -- until we are sure all the administrative items are confirmed (google apparently accidently informed 1800 people they were accepted and then had to retract). Eventually the list should show up here: http://code.google.com/soc/boost/about.html Jeff

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[Serialization] Serializing a map
by Christian Henning 25 May '06

25 May '06

Hi there, I was just toying around with the boost serialization lib. Unfortunately I have a problem with serializing a map. Here is what I did: #include <map> #include <string> #include <iostream> #include <algorithm> #include <fstream> #include <boost/archive/text_iarchive.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/serialization/map.hpp> using namespace std; struct Settings { int Brightness; int Contrast; }; // Table indexed by strings typedef pair< string, string > Key; typedef map< Key, Settings* > Table; int _tmain(int argc, _TCHAR* argv[]) { Table aTable; aTable[ make_pair("Mueller","Meier") ] = new Settings(); aTable[ make_pair("Meier","Mueller") ] = new Settings(); aTable[ make_pair("Meier","Meier") ] = new Settings(); Settings* pSettings = aTable[ make_pair("Mueller","Meier") ]; pSettings->Brightness = 99; pSettings->Contrast = 8; ofstream ofs( "Settings.txt" ); boost::archive::text_oarchive oa( ofs ); oa << aTable; return 0; } I get an the following error: error C2027: use of undefined type 'boost::STATIC_ASSERTION_FAILURE<x>' .... I'm using MSVC 7.1 and boost 1.33.1 . I believe there is something very basic wrong in my code. Any help? Thanks ahead, Christian Henning

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Shmem timed mutex
by Steven Wooding 25 May '06

25 May '06

Hi, I wonder if you can help me. I'm using the Shmem library (v0.92) and I'm trying to use a shared_timed_mutex with a scoped_timed_lock. This seems to work until the mutex is about to go out of scope. Then my program just hangs. It seems that it can not unlock the mutex. I tried issuing a "unlock" function call on the lock object and that hangs as well. Could anyone confirm if the shared_timed_mutex works at the moment. Thanks for you help. Steve.

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Access violation in Boost.Format using absolute tabulations
by Edson Tadeu 25 May '06

25 May '06

If the format string have an absolute tabulation (%t), the basic_format::clear() method throws an access violation because of this piece code in format_implementation.hpp(138): if( bound_.size()==0 || !bound_[ items_[i].argN_ ] ) Here items_[i].argN_ can be negative (defined in internals.hpp(70)), which is an invalid index to bound_[]. I think a simple check of greather than zero would suffice to fix it. Here is a code that catches it: using boost::format; format f("%0s%-32.32s:%|40t|%|.6|%|55t|%25s\n"); f % "test1" % 2.0 % "test3"; f % "test4" % 5.0 % "test6"; // calls clear() and breaks

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[Variant] Time complexity of apply_visitor
by Scott Meyers 25 May '06

25 May '06

If I invoke apply_visitor, what is the time complexity wrt the number of types that may be in the variant? The doc doesn't seem to address this. I looked at the source code, but all I can remember before my head exploded due to exposure to the MPL and the PPL was "switch" (which suggests constant time) and "unrolling" which suggests either linear or constant time, depending on what is being unrolled. Does anybody know what the time complexity of apply_visitor is? My real question is whether applying a visitor to a variant is more efficient than a cascading series of calls to get. I know that the following runs in linear time wrt the number of types in the variant, if (T1 *p = get<T1>(&myVariant)) ... else if (T2 *p = get<T2>(&myVariant)) ... else ... else if (Tn *p = get<Tn>(&myVariant)) ... but what about this? apply_visitor(myVisitor, myVariant); Thanks for any enlightenment. Scott

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[multi_array] size_type
by Daniel Mitchell 24 May '06

24 May '06

It seems clear that since each dimension of a multi_array can have (I presume) extent up to numeric_limits<size_type>::max(), size_type isn't always large enough to hold the actual size of the multi_array and multi_array::size() may overflow. I have a similar problem with some of my own code, and I'd like to know how the multi_array designers approached this problem--my approach so far is to punt the problem to my users. Thanks. D.

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multi_array index_gen or extent_gen store for reuse
by Levent 24 May '06

24 May '06

Is it possible to store tuples of index or range values (or generators) for later reuse? Consider the following: typedef boost::multi_array<int,3> Arr; typedef Arr::index_range Ir; typedef ??? indices; Arr a(boost::extents[3][4][5]); Arr b(a); indices somerange = Arr::index_gen[Ir()][Ir(1,5)][Ir()<2]; b[somerange] = a[somerange]; // and so on What should `???' be? thanks - Levent

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[boost.multi_array] Question about iterators on multi_array_views
by bernhard.maeder＠zkb.ch 24 May '06

24 May '06

Hello everyone I'm trying to use the boost.multi_array's iterators and came across a problem: calling end() on a certain multi_array_view only yields the same iterator, if it is called on exactly the same instance of the view. When, however, the view is created twice (using the same expression, of course), end() produces an iterator that doesn't compare to the first one. In other words: m_a[indices[index_range()][1]].end() != m_a[indices[index_range()][1]].end() I'm not sure whether this is just me, trying to use something in a way it shouldn't be used, or if this is a limitation of the multi_array library. I'd appreciate your opinion! Thanks a lot! Bernhard Maeder Following is the code that produces an error due to using the multi_array in the above manner: ----------------------------------------------------------------- #include <iostream> #include <boost/multi_array.hpp> using namespace boost; typedef boost::multi_array_types::index_range index_range; using boost::indices; template<typename IteratorType> void output(IteratorType begin, IteratorType end) { for (IteratorType it = begin; it != end; ++it) { std::cout << *it << std::endl; } } template<typename ArrayType> void output(ArrayType const & ar) { std::cout << "----------" << std::endl; std::cout << (ar.end() == ar.end()) << std::endl; std::cout << "----------" << std::endl; output(ar.begin(), ar.end()); } int main() { typedef boost::multi_array<double, 2> array_type; // Create a 3x3 array: array_type m_a(boost::extents[3][3]); for (std::size_t i=0; i<9; i++) m_a.data()[i] = static_cast<double>(i); // Works: std::cout << "Use a sub_array:" << std::endl; output(m_a[1]); // Works: std::cout << "Use a multi_array_view:" << std::endl; output(m_a[indices[index_range()][1]]); // Doesn't work: std::cout << "Use subsequent versions of a multi_array_view:" << std::endl; // This returns false: std::cout << "----------" << std::endl; std::cout << ( m_a[indices[index_range()][1]].end() == m_a[indices[index_range()][1]].end() ) << std::endl; std::cout << "----------" << std::endl; output( m_a[indices[index_range()][1]].begin() , m_a[indices[index_range()][1]].end() ); return 0; } ___________________________________________________________________ Disclaimer: Diese Mitteilung ist nur fuer die Empfaengerin / den Empfaenger bestimmt. Fuer den Fall, dass sie von nichtberechtigten Personen empfangen wird, bitten wir diese hoeflich, die Mitteilung an die ZKB zurueckzusenden und anschliessend die Mitteilung mit allen Anhaengen sowie allfaellige Kopien zu vernichten bzw. zu loeschen. Der Gebrauch der Information ist verboten. This message is intended only for the named recipient and may contain confidential or privileged information. If you have received it in error, please advise the sender by return e-mail and delete this message and any attachments. Any unauthorised use or dissemination of this information is strictly prohibited.

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[shared_ptr] locking issues in Multithreads and singlethreaded env.
by Kobi Cohen-Arazi 24 May '06

24 May '06

Hi As far as we know, boost::shared_ptr has a locking overhead when inc/dec is invoked. I wonder: 1. Is it using atomic op? 2. Why Alexandrescu policy based shared_ptr was rejected? 3. What can we do in order to be able to use shared_ptr without that overhead? Thanks, Kobi.

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