December 2008 - Boost-users - lists.preview.boost.org

[non Boost] Template troubles.
by Robert Jones 12 Dec '08

12 Dec '08

Ok, first off, this is not explicitly about Boost, which I know is against the Boost guidelines, but I hope you'll all forgive me. Indirectly it is through trying to use Boost that i've bumped into this. A little code snippet... #include <cstddef> template < typename T, std :: size_t sz > struct Block { typedef T type[ sz ][ sz ]; }; template < typename T > void assign( T & assignee, const T & value ); template < typename T, std :: size_t sz > void assign( T ( & assignee )[ sz ], const T ( & value )[ sz ] ); int main( ) { Block< int, 16 > :: type a; const Block< int, 16 > :: type b = { }; assign( a, b ); } This compiles under Gcc & Comeau, but MS VisStudio reckons the call to assign in main is ambiguous. Any thoughts? Also, if I put all the template declarations in an anonymous namespace, Comeau fails to compile, while Gcc is still ok! Have we encountered this before, and is there a known work around? Thanks. - Rob.

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Thread and exception
by Janne Kätevä 12 Dec '08

12 Dec '08

Hi I have noticed that on Ubuntu my code that uses Boost Threads works fine when I throw exceptions (for example strings) and catch them in the same thread. But this doesn't seem to work on Windows XP with Mingw gcc 3.4.5. If I throw a exception in thread, the program crashes. Is there some known problem with Boost Thread and Mingw? I'm using Boost 1.37. Simple example: #include <exception> #include <boost/thread/thread.hpp> using namespace std; class callable { public: void run() { try { cout << "Throwing" << endl; throw string("error"); } catch(string &e) { cout << "Error: " << e << endl; } } void operator()() { this->run(); } }; int main() { callable c; boost::thread thrd(boost::ref(c)); thrd.join(); return 0; } Janne

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handle different endian
by boost001 12 Dec '08

12 Dec '08

Does Boost have method to do endian swap, like those ntohl and htonl? -- View this message in context: http://www.nabble.com/handle-different-endian-tp20979512p20979512.html Sent from the Boost - Users mailing list archive at Nabble.com.

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[program_options] word-wrapping broken in presence of default arguments
by Peter Simons 12 Dec '08

12 Dec '08

Hi, in Boost 1.37.0, this program #include <iostream> #include <string> #include <boost/program_options.hpp> int main(int argc, char * argv[]) { using namespace std; using namespace boost::program_options; options_description cmdline_options("Supported options"); cmdline_options.add_options() ("help", "this is a sufficiently long text to require word-wrapping") ("prefix", value<string>()->default_value("/h/proj/tmp/dispatch"), "root path of the dispatch installation") ; cerr << cmdline_options << endl; return 0; } displays a usage message that looks weird: $ g++ foo.cpp -lboost_program_options.a && ./a.out | Supported options: | --help this is a sufficiently long text to requ | ire word-wrapping | --prefix arg (=/h/proj/tmp/dispatch) root path of the dispatch installation It appears that the word-wrapping algorithm can't handle the default argument properly. Is that a known problem? Can I work around that somehow? I also wonder whether it's possible to format the help string such that it's printed in the *next line*, like this: | --prefix arg (=/ridiculously/long/path/that/leaves/no/room/on/right/side) | root path of the dispatch installation I tried adding a '\n' at the beginning of the help string, but that didn't have the desired effect. Is there any way to accomplish this? Take care, Peter

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[Serialization] Confusing problem serializing a vector of pointers to a base class
by Martin Weinberg 12 Dec '08

12 Dec '08

I'm struggling debugging a problem with recent versions >1.35. I have a huge code with a boost-serializaton-based persistence system. In short, all "persistent" classes derive from a base class. The code keeps track of the instances by a vector to pointers to the base class. Starting with version 1.36, saving the archive results in the following run-time message: /usr/local/boost_1_37_0/include/boost-1_37/boost/archive/impl/archive_pointer_oserializer.ipp:64: static const boost::archive::detail::basic_pointer_oserializer* boost::archive::detail::archive_pointer_oserializer<Archive>::find(const boost::serialization::extended_type_info&) [with Archive = boost::archive::polymorphic_oarchive]: Assertion `it != boost::serialization::singleton< oserializer_map<Archive> >::get_const_instance().end()' failed. I would be good, I know, to post a snippet that produces the error. Unfortunately, I've tried unsuccessfully for some time to make this occur in a simple test code with similar features to the main code. Can someone give me any pointers that would help me debug this? After a >3 days of struggle, I'm at a loss. Again, there are no problems with 1.35. I'm not suggesting that the error is not of my own making but maybe this is a clue. TIA!

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The "error C2668" on VC6
by wind world 12 Dec '08

12 Dec '08

Hi guys, I'm trying to introduce the boost regex into my old VC6 project. "using namespace std" is declearared in many files. When I include "#include <boost/regex.hpp>", I receive the following error: error C2668: 'memset' : ambiguous call to overloaded function. When I remove "using namespace std" or add :: to memset(memset -> ::memset), it can be ok. I want to ask wheather there is the third way to solve this problem. Appreciate any help. Worldwind

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Proto: extending the example mixed.cpp
by Kim Kuen Tang 11 Dec '08

11 Dec '08

Hi all, i wnat to extend the example in the file mixed.cpp with an operator[]: double operator []( std::ptrdiff_t i ) const { DereferenceCtx const deref = {}; AdvanceCtx adctx(i); //just shift the iterator with std::advance typename boost::result_of<Begin(Expr const &)>::type expr2 = Begin()(*this); proto::eval(expr2,adctx); return proto::eval(expr2, deref); } This works well. However is it possible to let proto figure out what the result_type of this function is? I've tried to program in this way. typedef typename boost::result_of<Begin(Expr const &)>::type Expr2; typedef typename proto::result_of::eval<Expr,DereferenceCtx>::type result_type; result_type operator []( std::ptrdiff_t i ) const { DereferenceCtx const deref = {}; AdvanceCtx adctx(i); Expr2 expr2 = Begin()(*this); proto::eval(expr2,adctx); return proto::eval(expr2, deref); } But the compiler complained that the nested struct eval in the struct struct DereferenceCtx { template<typename Expr, typename EnableIf = void> struct eval : proto::default_eval<Expr, DereferenceCtx const> {}; cannot be instantiated by this particulat template. So I guess I ' ve to write a grammar for this issue. Is this true?

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[BGL] Matrix as Graph - Graph Adaptor
by Liao, Elizabeth 11 Dec '08

11 Dec '08

Hi, I'm looking at using the Graph Adaptor class for Matrices but I'm not sure how to use it. Specifically, I'm confused by the macro BOOST_GRAPH_ADAPT_MATRIX_TO_GRAPH in matrix_as_graph.cpp. Does anyone have an example on how to use it? I'm more at the evaluation stage on whether to use BGL or not so I'm not familiar with other BGL functions. Any help would be appreciated. Thanks! Liz

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More on: Problem solved: LNK2019 with boost::thread_group [!]
by Joseph A. Marks 11 Dec '08

11 Dec '08

Thanks, Steve, I get this in thread form so your great reply isn't included here. (AMDG). We often (though not always) have the following line also: using boost::unit_test_framework::test_suite; My coding standards manual says only to put using directives in .cpp files rather than .h (or .hpp) files. Joseph A. Marks PHONE: 612-788-9658 e-mail: josephamarks(a)yahoo.com --- On Thu, 12/11/08, Joseph A. Marks <josephamarks(a)yahoo.com> wrote: > In case anyone ever needs to know, here are the steps taken > to solve the problem: {NOTE: A colleague helped me with > this}. > > Re-loaded Boost, upgrading to v. 1.37 {this upgrade may be > a red herring, but it didn't hurt). This version is > very friendly to compiling in MS VS 2008 (version 9). > > Then, added the following, at the top of any relevant file: > > #include <boost/test/floating_point_comparison.hpp> > > #define BOOST_TEST_MAIN "Test > put_your_town_string_here" > #include <boost/test/unit_test.hpp> > #include <boost/test/auto_unit_test.hpp> > > I am not sure if the first of these includes is required, > but this always seems to work. > > Hopefully, someone will be helped by this e-mail at some > point or other. > > Thanks, > Sincerely, > > Joseph A. Marks > e-mail: josephamarks(a)yahoo.com > > > --- On Mon, 12/8/08, Joseph A. Marks > <josephamarks(a)yahoo.com> wrote: > > > From: Joseph A. Marks <josephamarks(a)yahoo.com> > > Subject: LNK2019 with boost::thread_group [!] > > To: boost-devel(a)lists.boost.org > > Date: Monday, December 8, 2008, 10:53 AM > > I get the following linker error using Boost, I am > trying to > > get it to compile using VS 2008, with a makefile > system: > > > > error LNK2019: unresolved external symbol "class > > boost::unit_test::test_suite * __cdecl > > init_unit_test_suite(int,char * * const)" > > > (?init_unit_test_suite@@YAPAVtest_suite@unit_test@boost@@HQAPAD@Z) > > referenced in function _main > > > > Does anyone have any insight? > > > > Thanks in advance, > > > > Joseph A. Marks > > e-mail: josephamarks @ yahoo.com > > Joseph A. Marks > e-mail: josephamarks(a)yahoo.com Joseph A. Marks PHONE: 612-788-9658 e-mail: josephamarks(a)yahoo.com

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maybe ot: debugger expression evaluators
by Noah Roberts 11 Dec '08

11 Dec '08

Does anyone know of any set of VS evaluators ( http://msdn.microsoft.com/en-us/library/8fwk67y3(VS.80).aspx ) that would make debugging code that uses some of the more internally complex boost constructs a bit easier? Ones I can think of that would make life easier: whatever is returned by bind smart pointers (not so bad right now actually) boost::function others? For instance, with the bind it would be nice to see simply the address of the function and an array of the arguments...with some obviously being displayed as "placeholder". The boost::function one could maybe just show the function object it stores. Currently, to get to this information you have to weed through quite a few levels of abstraction. Not saying this is bad, it's obviously necessary, but it can make debugging through these objects a bit of a hassle.

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