March 2008 - Boost-users - lists.boost.org

A possible bug in Boost.property_tree with UNICODE XML file?
by Tan, Tom (Shanghai) 03 Mar '08

03 Mar '08

I am trying read_xml() on an xml-format config file, which starts like this: <?xml version="1.0" encoding="UTF-16"> ..... This file is well-formed and verified by "XML Copy Writer", it can also be open by IE or Filefox with no problem. I am using this code snippet to parse this file: try{ read_xml<wptree>(xmlfile,pt); } catch(xml_parser-error e) { e.what(); } and it throws an exception saying "expected <". By looking into the code I found that, this caused by the fact that the xmlfile starts with a Unicode Byte Order Mark (BOM)-0xFFFE . "fffe 3c00 3f00 7800 ......" However, read_xml() cannot handle this BOM byte and throws. It's easy to fix it by simply discard the BOM byte, but I wonder whether there is already a flag to enable/disable this that I am unaware of. Can anyone help to clarify? Thanks, tom

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Re: [Boost-users] templates: parts of functions
by Lang Stefan 03 Mar '08

03 Mar '08

Hi, As I am not overly familiar with boost or it's mpl library yet, I cannot provide any specific advice along these lines. According to your description, my advice would be to create helper template classes or functions that rely only on some of the template parameters of your actual template class, but not N. For these helper functions and classes you do not need partial specialization, and thus no duplicate code. Depending on the complexity of your functions you might also extract those parts that do not depend on N into more template functions. If these helpers need access to private members of your makeTree class, you can declare them friend. (you might need to replicate those friend declarations in your partial specializations) For those parts of the code that do depend on N, but do not need a different implementation, you may still provide templated helper classes. The compiler will still generate multiple class implementations for different values of N, but you won't need to replicate the actual code yourself. Hope this helps. Cheers, Stefan > ------------------------------ > > Message: 6 > Date: Sat, 1 Mar 2008 14:38:34 +0100 > From: "Hicham Mouline" <hicham(a)mouline.org> > Subject: [Boost-users] templates: parts of functions > To: <boost-users(a)lists.boost.org> > Message-ID: <000001c87ba1$8cfe0d30$a6fa2790$@org> > Content-Type: text/plain; charset="us-ascii" > > Hi, > > > > I have a function makeTree whose behavior depends on 3 > different policies > > typename T1 > > typename T2 > > int N > > > > For performance reasons, I need to write the 2- and 3- specializations > alongside the general N case. That is, the 2- and 3- default > > instantiations generated from the N case by the compiler are > not optimal. > > > > As it is impossible to write function templates partial > specializations, I > encapsulate the > > > > template< typename T1, typename T2, int N> void > makeTree(Head<N>&, const > T2&, const C&) ; > > > > function in a class template > > > > template< typename T1, typename T2, int N> class makeTree{ > > void makeTree(Head<N>&, const T2&, const C&); > > }; > > and write the partial specializations <T1,T2,2> and <T1,T2,3>. > > > > > > Now, this makeTree function is quite large. It includes code that : > > . doesn't depend on any of the template arguments > > . code that depends only T1 > > . code that depends only on T2 > > . code that depends only on N > > . code that depends only on <T1,N>. > > > > I am worried about code bloat, and the effect on overall > performance of the > actual code generated even if it is not run > > (I noticed substantial effects depending on the size of > object files and > final shared library generated). > > > > Besides this, I suppose it is a better design to have these > segments of code > put in template functions > > with the right template arguments. > > > > Is it MPL the library that I should look into for such work? > > Perhaps nothing in Boost particularly facilitates this work, > and std c++ > templates are enough, > > > > Thoughts, comments are appreciated, > > > > Rds, >

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Why does runtime-debugging set _STLP_USE_DYNAMIC_LIB?
by Eric Woodruff 02 Mar '08

02 Mar '08

I've been trying to understand why the debug version of boost was attempting linkage with the DLL version of stlport (which I didn't build and I'm not using) and now I see that the runtime-debugging flag is specifying that the dynamic library must be used. This causes the static stlport to use the stlpdx cross namespace rather than the stlpd namespace. It is not obvious to me why debugging should require a dynamic library. Under code inspection this looks like a copy-paste oversight. if [ $(rproperties).get <runtime-debugging> ] = "on" { usage-requirements += <define>_STLP_DEBUG=1 <define>_STLP_DEBUG_UNINITIALIZED=1 ; } if [ $(rproperties).get <*runtime-debugging*> ] = "on" { usage-requirements += <define>_STLP_USE_DYNAMIC_LIB=1 ; } Why would it be checking for runtime-debugging twice? I think the second if should check for <runtime-link> which has the possible values "static" or "dynamic". This problem looks related to this thread: http://lists.boost.org/boost-users/2007/09/30905.php, but I couldn't find the Boost.Build message that is a follow-up to that one. I haven't found a posted solution either. Looking at the CVS HEAD revision of stlport.jam, it hasn't changed since 1_34_1. So if this is a bug, it has not been fixed yet. Thanks, Eric

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Re: [Boost-users] fatal error C1128: object file format limit exceeded : more than 65, 279 sections -------PROBLEM SOLVED
by jono 02 Mar '08

02 Mar '08

i thought i had broken the translation unit in two, but it was a clever illusion ... doh.

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fatal error C1128: object file format limit exceeded : more than 65, 279 sections
by jono 02 Mar '08

02 Mar '08

hi, i've received this error compiling a project under visual studio 7.1. "fatal error C1128: object file format limit exceeded : more than 65,279 sections" the problem appeared when i added a couple more specializations to a 'binary operator' visitor for manipulating boost variant objects. before this, there were 20 or 30 similar specializations compiling without errors or warnings. the visitor and helpers are as follows: =========================== template<BinaryOp op, typename ObjectT, typename ObjectU> Object binary_op(const ObjectT &arg1, const ObjectU &arg2) { return undefined; } template<BinaryOp op, typename ObjectT> Object binary_op(const ObjectT &arg1) { return undefined; } template<BinaryOp op> class BinaryOpVisitor : public boost::static_visitor<Object> { public: template<typename ObjectT> Object operator()( const ObjectT &arg0) const; { return binary_op<op, ObjectT>(arg0); } template<typename ObjectT, typename ObjectU> Object operator()( const ObjectT &arg0, const ObjectU &arg1) const { return binary_op<op, ObjectT, ObjectU>(arg0, arg1); } }; ======================== and specialized: ======================== template<> INLINE Object binary_op<ADD>(const Integer& arg0, const Integer& arg1){return make<Integer>(arg0 + arg1);} .... .... .... .... etc etc ======================== the variant type looks like this.... ======================== typedef boost::make_recursive_variant< Nil ,Integer ,Real ,String ,Error ,Class ,Character ,Stream ,Boolean ,boost::recursive_wrapper< Symbol > ,boost::recursive_wrapper< Lambda > ,boost::recursive_wrapper< Function > ,boost::recursive_wrapper< Pair > >::type Atom; ======================== i imagine there are some combinatorial proliferations of template instantiation going on in the compiler. the operators were declared inline, but removing that didn't fix the error. i've restructured the source code in other ways, but without success so far. visual studio 8 has a compiler switch /bigobj to resolve this problem: "By default, an object file can hold up to 65,536 (2^16) addressable sections. /bigobj increases that address capacity to 4,294,967,296 (2^32)." i haven't tried compiling this project with g++ since making these changes (haven't checked them in) so i don't know what its limits are. does anyone has experience with solving this problem. is it a problem with my visitor class? is there a way i can break my recursive variant down for the compiler? cheers, Jono Poff

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a difference of boost.function between g++4.13 and vc8
by 钱晓明 02 Mar '08

02 Mar '08

I wrote some code using boost.function. Compiling it both in g++4.13 and vc8, I find that I can not declare a struct in function with operator() and use boost.function to call it when I use g++. Just like this: int main() { struct int_div { float operator()(int x, int y) const { return ((float)x)/y; }; }; boost::function<float (int x, int y)> f = int_div(); std::cout << f(5, 3) << std::endl; return 0; } When I compile the code above in g++, it give me the error : 请求从 'main()::int_div' 转换到非标量类型 'boost::function<float ()(int, int), std::allocator<void> >'(I use ubuntu chinese.) but when I move the int_div definition outside of main(), It is ok! And the code above VC8 can compile it! why?

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Re: [Boost-users] [boost] Serialization of Range library's sub_range
by brass goowy 01 Mar '08

01 Mar '08

Brian Wood writes: >Recently, I suggested there should be serialization support wrt >the Range library - >http://lists.boost.org/Archives/boost/2008/01/132294.php. >I'm writing to inform you of my plans in this regard. This input: > >Msgs > (sub_range<list<short> >) @OUT >} > >to the C++ Middleware Writer, http://home.seventy7.com/cgi-bin/samb.cgi, >results in this output: > >#include <boost/range/sub_range.hpp> >#include <list> >#include <Buffer.hh> >using boost::sub_range; > > >struct Msgs >{ >inline >Msgs() {} >inline >~Msgs() {} > >inline >int >Send(Buffer* buf, const sub_range<list<short> >& about1) >{ > unsigned int headCount = 0; > headCount = about1.size(); > if (!buf->Receive(&headCount, sizeof(int))) { > buf->ews_.SetErrorWords(1, __FILE__, __LINE__); > return 0; > } > list<short>::const_iterator rit1 = boost::begin(about1); > list<short>::const_iterator rit2 = boost::end(about1); > for (; rit1 != rit2; ++rit1) { > if (!buf->Receive(&(*rit1), sizeof(short))) { > buf->ews_.SetErrorWords(1, __FILE__, __LINE__); > return 0; > } > } > > if (!buf->SendStoredData()) { > buf->ews_.SetErrorWords(2, __FILE__, __LINE__); > return 0; > } > return 1; >} > >}; > >This functionality isn't available online yet. G-d willing, it >will be available by the middle of next month. Update: the functionality is now available online. Brian Wood Ebenezer Enterprises www.webebenezer.net

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Boost file system idiocy
by Patrick Loney 01 Mar '08

01 Mar '08

Can't find how to seek to eof, currently using: fs.seekp( (std::streamoff)boost::filesystem::file_size( SKDO::ArchiveFilePath( keyname ) ) ); please help ****************************************************************************** "This message and any attachments are solely for the intended recipient and may contain confidential and privileged information. If you are not the intended recipient, any disclosure, copying, use, or distribution of the information included in this message and any attachments is prohibited. If you have received this communication in error, please notify us by reply e-mail and immediately and permanently delete this message and any attachments. Thank you." Interactive Transaction Solutions Ltd (2473364 England) Registered Office: Systems House, Station Approach Emsworth PO10 7PW ********************************************************************** Ce message �lectronique contient des informations confidentielles � l'usage unique des destinataires indiqu�s, personnes physiques ou morales. Si vous n'�tes pas le destinataire voulu, toute divulgation, copie, ou diffusion ou toute autre utilisation de ces informations, est interdite. Si vous avez re�u ce message �lectronique par erreur, nous vous remercions d'en avertir son exp�diteur imm�diatement par email et de d�truire ce message ainsi que les �l�ments attach�s. Interactive transaction Solutions SAS- France (RCS Pontoise : 489 397 877) Si�ge social : Parc Saint Christophe, 10, Avenue de l�Entreprise 95865 Cergy-Pontoise Cedex ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________

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Couting occourance of specified characters
by Olaf Peter 01 Mar '08

01 Mar '08

Hi, the snipped attached counts the accourance of a specified character. Is there a simpler way using the boost libs? This solution looks quite overkill. It should be fast ;-) Thanks, Olaf

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Bind + Function + Arguments
by QbProg 01 Mar '08

01 Mar '08

Hello there, I've started using boost function and bind features , and I'd like to find a way to do the following. You can take it as suggestion, if it is not implemented :) I would like to use the bind function on object members in the same way indipendently of the number of arguments. For example: function <void (int , int ) > FunctionOne; function < bool (int ) > FunctionTwo; class Implementor { public: void ImplOne ( int , int ); bool ImplTwo ( int ); }; void test () { Implementor i; FunctionOne = bind ( &Implementor::ImplOne , &i , _1 , _ 2); FunctionTwo = bind (&Implemenetor::ImplTwo, &i , _1); /* I Would be nice to do something like this, with parameter "guessing" */ // FunctionOne = GenericBind ( &Implementor::ImplOne ,&i); // FunctionTwo = GenericBind ( &Implementor::ImplTwo, &i); /* This will greatly remove verbosity! */ /* Actually I do */ #define Bind0(A,B) bind(A,B) #define Bind1(A,B) bind(A,B,_1) #define Bind2(A,B) bind(A,B,_1,_2) ...... FunctionOne = Bind2 ( &Implementor::ImplOne , &i ); FunctionTwo = Bind1 ( &Implementor::ImplTwo , &i); } It would be usefoul to make library callbacks more usable, insteat of writing a long list of arguments each time. It is possible with current implementation? I ask you for any suggestion, Thank you QbProg

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