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question on using BOOST_FOREACH with non-stl container
by Michael W Daniels 12 Mar '05

12 Mar '05

In experimenting with the new BOOST_FOREACH header, I'm getting the compile error (MSVC 7.1) below with this code. The documentation for BOOST_FOREACH says: >The support for STL containers is very general; anything that looks like >an STL container counts. If it has nested iterator and const_iterator >types and begin() and end() member functions, BOOST_FOREACH will >automatically know how to iterate over it. I've checked, and the hashed_array_tree class does have nested iterator and const_iterator types, as well as begin() and end() member functions. (It's originally from www.cphstl.dk, but that site no longer provides the code.) Replacing hashed_array_tree with vector gets rid of the error, so there's obviously something I need to fix in the hashed_array_tree. How do I figure out what that is, though? Any help will be greatly appreciated. ===code=== #include <memory> #include <iostream> #include "foreach.hpp" #include "math_utils.hpp" #include "hashed_array_tree.hpp" #include "hat_iterator.hpp" using namespace std; using namespace boost; using namespace cphstl; class A { public: int foo; }; void test() { const hashed_array_tree<const A*>* Ahat = new hashed_array_tree<const A*>(); BOOST_FOREACH(const A* curA, *Ahat) cout << curA->foo; } ====== ==error== e:\Projects\gidlp\fsparser\foreach.hpp(455) : error C2440: 'return' : cannot convert from 'const std::allocator<_Ty>::value_type' to 'boost::iterator_reference<Iterator>::type' with [ _Ty=const A * ] and [ Iterator=boost::range_const_iterator<cphstl::hashed_array_tree<const A *>>::type ] Conversion loses qualifiers e:\Projects\gidlp\fsparser\test2.cpp(20) : see reference to function template instantiation 'boost::iterator_reference<Iterator>::type boost::for_each::deref<cphstl::hashed_array_tree<T>,boost::mpl::true_>(boost::for_each::static_any_t,boost::for_each::container<cphstl::hashed_array_tree<T>,C>)' being compiled with [ Iterator=boost::range_const_iterator<cphstl::hashed_array_tree<const A *>>::type, T=const A *, C=boost::mpl::true_ ] ====== -- Michael W. Daniels | Choreography is its own reward. daniels(a)ling.osu.edu | Some things are done only for the sake Doctoral Candidate | of form. Don't fight it by looking for Department of Linguistics | substance in everything.

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boost::threads is it all about managed threads?
by The Grumpiest Man You Know 11 Mar '05

11 Mar '05

I realize I might be trying to read beyond my experience level but I am having a blast and might even be getting somewhere learning a new programming style, a little. :) So, I've been looking at boost::threads and pthreads while considering a problem. I was never a believer in threads, I come from an SMP background and always found that for what I wanted to do, async IO beat the pants off threads. Not that I want to start a war, just that I want to explain why I'm happy with concurrent programming but a complete nonce case when discussing thread programming. I have an application in mind for comparison and it's not particularly complex but it's a monster in LOC, mainly due to the liberal use of FORTRAN in whatever language the compiler happens to take. But one of the things it does have, that I'd rather not re-implement, is a request service library. That library picks up an incoming request, goes and carries out the action and then returns the result. The requests are of unbounded duration and there are multiple clients so the service times are pretty sad. I think that sounds like a job for threads; no need to alter the service code, just replace the routine that returns the results and bob's your mum's brother and I can get 10 at a time all sleeping waiting for the requested IO. But to not scare the natives I'd prefer to have a single thread unless the load actually demands more. Now, my old C brain can see that the main thread can get it's thread ID from thread_self() and then just be one of the guys but I can't see how the boost::thread() can do anything but give me threads to manage. After stepping on myself with a vector<boost::thread> :) I think this is the tao of boost::thread: const boost::function0<void> run = &go; boost::thread_group grp; for(int i = 0; i < 100; i++) { grp.create_thread(go); } grp.join_all(); Is that right? What am I missing? How do I get a bunch of peer boost::threads? If you're still with me thanks very much for your time and help and let me know if I'm dragging the list off topic and I'll go find someone else to bug. -- Blue Skies

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RE: [Boost-users] __stdcall with boost::function
by Olenhouse, Jason 11 Mar '05

11 Mar '05

Ben Hutchings wrote: > Olenhouse, Jason wrote: > > I'm trying to pass a member function pointer around to the Windows > > Service Control Manager through Windpws API functions, but > > I think I'm having troubles with the __stdcall convention. > <snip> > > No, the problem is passing a member function pointer. A > member function > pointer is not type-compatible with a function pointer with the same > parameter types, regardless of whether they have the same calling > convention. <snip> But I used boost::bind to get a function pointer to hide the implicit this. I thought that the purpose of boost::bind was for that reason. It seems that the way I did it was nearly successful other than function::target<>() returns a __cdecl function pointer instead of an __stdcall one, as indicated by the error that MSVC returns. Is my interpretation of what I'm seeing incorrect? BTW, I included the two defines, #define BOOST_BIND_ENABLE_STDCALL #define BOOST_MEM_FN_ENABLE_STDCALL to be able to bind __stdcall member function with the this object pointer (I forgot to mention this in the original post). -Jason

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Re: Re: Serialization, multiple inheritance, bad cast at smart_cast.hpp:202
by Zoltan Szatmary 11 Mar '05

11 Mar '05

Dear Robert thank you for answering. > > class A > > class B : public A > > class C : public virtual B > > class D : public virtual B > > class E : public C, public D > > > > so, a classic diamond inheritance which the serialization lib is > > supposed to be able to tackle with. Now, if I have a piece of code > > like this > > > > boost::serialization::xml_oarchive oa(somestream); > > A *a = new E(); > > oa << BOOST_SERIALIZATION_NVP(a); > > > > it throws exception at the aforementioned line. Examining the template > > substitutions, template class T is substituted with const B* and > > template class U is substituted with const A. So, the program should > > do a downcast on a const A* to const B* which is ought to be possible. > > Your example does indicate whether A has any pure virtual functions or not. > The dynamic down cast will only function if A is polymorphic - that is has > at least one virtual function. Soooo, I would expect this work if A has at > least one virtual function and I would expect it to fail if has no virtual > function. Double check this and get back to us. Yes, A does have a virtual destructor. But originally A had more virtual member functions, I just trimmed them down when I wanted to locate the source of error. But yes, class A is still polymorphic. I try to attach the example code to this mail, I hope it will get through. Best regards Zoltan

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when to use libboost_xxx-mt ?
by Oliver Kowalke 11 Mar '05

11 Mar '05

Hello, afaik '-mt' stands for multithreading. Do I've to link against the '-mt' version of a boost library if my application is single threaded but uses external libs which internally span threads? Could you be so kind to give me a generall guideline? thx Oliver -- SMS bei wichtigen e-mails und Ihre Gedanken sind frei ... Alle Infos zur SMS-Benachrichtigung: http://www.gmx.net/de/go/sms

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Serialization, multiple inheritance, bad cast at smart_cast.hpp:202
by Zoltan Szatmary 11 Mar '05

11 Mar '05

Dear all I use the serialization library of boost, and I am very satisfied with it except one annoying issue. It turns out, that in many cases (not always!!!) when there is a multiple inheritance structure in the class hierarchy I am trying to serialize I get a std::bad_cast exception at line 202 in smart_cast.hpp. The corresponding boost code is: template<class U> static T cast(U * u){ T tmp = dynamic_cast<T>(u); #ifndef NDEBUG if ( tmp == 0 ) throw std::bad_cast(); #endif return tmp; } I have debugged it, and I could not really find out what the problem was. For example I have a class hierarchy similar to this: class A class B : public A class C : public virtual B class D : public virtual B class E : public C, public D so, a classic diamond inheritance which the serialization lib is supposed to be able to tackle with. Now, if I have a piece of code like this boost::serialization::xml_oarchive oa(somestream); A *a = new E(); oa << BOOST_SERIALIZATION_NVP(a); it throws exception at the aforementioned line. Examining the template substitutions, template class T is substituted with const B* and template class U is substituted with const A. So, the program should do a downcast on a const A* to const B* which is ought to be possible. The funny thing is, that the error does not always appear! I could put together a simple example code demonstrating this effect, but I am not sure that attachments to this mail get through the list server, so anybody kind enough to take a look at this problem can ask me to send him/her the example code. I have tested the example code both with Intel C++ compiler v8.1 and G++, so I concluded this may not be a compiler error but rather some boost flaw. Any help is warmly welcome and thanked in advance! Cheers Zoltan

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PC-Lint and boost 1.32.0
by Jarl Lindrud 10 Mar '05

10 Mar '05

Hi! Is anyone here running PC-Lint successfully on projects using Boost 1.32.0 ? When I run it (PC-Lint 8.00q), it winds up in an infinite loop while processing some headers from boost/mpl. There's a note about it on Gimpel's discussion boards, but no responses from them, unfortunately... Is anyone else having this problem? TIA! /Jarl

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Boost threads libraries? linking problem and question
by Roger Wilco 10 Mar '05

10 Mar '05

I have a large (at least non-trivial) C++ application that uses Boost threads. I am now trying to get it building as a Managed C++ (aka C++ .NET) application. The original unmanaged MFC application used the following import library: ..\boost\boost_1_32_0\bin\boost\libs\thread\build\boost_thread.dll\vc-7_1\release\threading-multi\boost_thread-vc71-mt-gd-1_32.lib The managed C++ Forms application requires that AND a second library which seems to be a static library and not an import library for a DLL: ..\boost\boost_1_32_0\bin\boost\libs\thread\build\libboost_thread.lib\vc-7_1\debug\runtime-link-static\threading-multi\libboost_thread-vc71-mt-sgd-1_32.lib It seems wrong that I need two Boost thread libraries to build with. Hoewver, my project won't build without both. There are apparently some #pragma-like instructions in the Boost source that trigger the linking of these libraries. If I do link with both Boost thread libraries, the project builds but gets bizarre exceptions at runtime that are buried in non-debuggable code. What is the difference between those Boost libraries? Which one is the one that I want? How can I stop the linker directives in the code from including the library that I shouldn't be using?

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Re: boost::bind problems with __cdecl and MSVC
by Daniel Boelzle 10 Mar '05

10 Mar '05

Hello Peter, > This can only happen if your default calling convention is something > other than __cdecl. This is very rare and boost::bind does not provide > explicit support for __cdecl, relying on it being the default. I am not forcing any specific calling convention: no /Gz (stdcall), /Gr (fastcall), nor /Gd (__cdecl) on my command line. MSDN documents that __cdecl is the default for vararg member functions, but thiscall for non-vararg member functions. The reason for decorating member functions with __cdecl is to get independent of the above mentioned switches when including those header files (thiscall cannot be specified, no keyword). regards, --Daniel

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Boost Unit Test with VC 7.1
by DrJekyll 09 Mar '05

09 Mar '05

Dear list member I have the problem with Unit Test. I am just creat new project file and copy the code from the start page http://www.boost.org/libs/test/doc/components/utf/getting_started/index.html but it does not compiled. I think the problem come from the work space configuration but I dont know exactly which point. Could someone share with me his experience on this matter? Best regards XS

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