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enable_shared_from_this2
by Peter Soetens 17 Feb '11

17 Feb '11

Hi list, I was in the need for a shared_from_this() in my constructor, so I chose this implementation for my class. Apart from the header being there and one mailing list thread, there's nothing that points to the existence of this header. Since we want to keep compatibility with Boost 1.38, I tried to backport the enable_shared_from_this2 class to that version. I was wondering why the weak_ptr::_empty() method was added to the weak_ptr API and why weak_ptr::expired() was not used instead ? I tried to emulate the same behavior by adding a 'bool' to the enable_shared_from_this2 class. Which works for my tests, but is there a pitfall to that solution ? Could I just replace this logic with weak_this_.expired() ? diff --git a/rtt/internal/enable_shared_from_this2.hpp b/rtt/internal/enable_shared_from_this2.hpp index a5bfcff..cb659f0 100644 --- a/rtt/internal/enable_shared_from_this2.hpp +++ b/rtt/internal/enable_shared_from_this2.hpp @@ -53,11 +53,13 @@ template< class T > class enable_shared_from_this2 { protected: - enable_shared_from_this2() + enable_shared_from_this2() : weak_init(false) { } - enable_shared_from_this2( enable_shared_from_this2 const & ) + // note: the copy constructor and operator= don't do anything, ie, they don't copy + // refcount status from the other object. + enable_shared_from_this2( enable_shared_from_this2 const & ) : weak_init(false) { } @@ -75,6 +77,7 @@ private: mutable weak_ptr<T> weak_this_; mutable shared_ptr<T> shared_this_; + mutable bool weak_init; // we deviate from the boost 1.40 implementation because weak_this_._empty() is not available in older versions. public: @@ -94,10 +97,11 @@ private: void init_weak_once() const { - if( weak_this_._empty() ) + if( !weak_init ) { shared_this_.reset( static_cast< T* >( 0 ), detail::esft2_deleter_wrapper() ); weak_this_ = shared_this_; + weak_init = true; } } @@ -111,6 +115,7 @@ public: // actually private, but avoids compiler template friendship issues if( weak_this_.use_count() == 0 ) { weak_this_ = shared_ptr<T>( *ppx, py ); + weak_init = true; } else if( shared_this_.use_count() != 0 ) { Thanks for any feedback, Peter

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[range] Using container find
by Robert Jones 17 Feb '11

17 Feb '11

The boost range library provides a smart version of begin/end that resolves to different things depending on whether its argument is a pair or something with its own begin/end method. Does a similar thing exist anywhere for find? Ie., if a find exists, eg,. for maps, then use it, otherwise fall back to std::find()? Thx - Rob.

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[Proto] Nested Types in Transforms
by Hossein Haeri 17 Feb '11

17 Feb '11

Dear all, In my namespace arity_caller, I have a struct CanBeCalled<> such that CanBeCalled<T, mpl::int_<n> >::type is an mpl::bool_<> representing whether T can be called with n doubles. I also have the following grammar (in a file called 'EmtnGram.hpp') in which I am trying to employ this CanBeCalled<>::type: struct EmtnShiftFObjGram: boost::proto::and_ < boost::proto::shift_right < EmtnTermOrGram, boost::proto::terminal<boost::proto::_> >, boost::proto::if_ < arity_caller::CanBeCalled < boost::proto::_value(boost::proto::_right), EmtnTermOrGram(boost::proto::_left) >::type > > {}; For an expression like x >> f, here, I am trying to make sure that f can be called with the right number of doubles -- that I have accumulated in x. When I compile this under GCC 4.5.1 (MinGW32, WinXP, SP3) and Boost 1.42, I get the following errors: In file included from main.cpp:5:0: EmtnGram.hpp:141:4: error: incomplete type 'arity_caller::CanBeCalled<boost::proto::_value(boost::proto::_child_c<1>), EmtnTermOrGram(boost::proto::_child_c<0>)>' used in nested name specifier EmtnGram.hpp:141:4: error: incomplete type 'arity_caller::CanBeCalled<boost::proto::_value(boost::proto::_child_c<1>), EmtnTermOrGram(boost::proto::_child_c<0>)>' used in nested name specifier EmtnGram.hpp:146:3: error: template argument 1 is invalid EmtnGram.hpp:147:2: error: template argument 2 is invalid Do I get it correctly that it's the ::type part of CanBeCalled<>::type that is confusing the compiler? Why is that happening? And, what's the cure? TIA, --Hossein

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[thread] equivalent of WaitForSingleObject
by Sean Farrow 16 Feb '11

16 Feb '11

Hi: I've got some boost code that calls wait for single object on windows. I'd like to transition this to use boost.thread. What is the best way of doing this, in the while loop I'm doing: while( WaitForSingleObject( hDir, WAIT_TIMEOUT ) != WAIT_OBJECT_0 ) Any help appreciated. Cheers Sean.

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[serialization] Undefined symbol
by John Reid 16 Feb '11

16 Feb '11

Hi, I'm trying to work on some code I haven't looked at in some time and in debug builds (with gcc 4.4.3) I keep getting an undefined symbol: boost::serialization::version<boost::multi_index::detail::serialization_version<bio::BindingHit<bio::BindingModel> > >::value I can't work out where this is getting referenced and why the compiler is not instantiating it there? Can anyone point me in the right direction? I'm using boost SVN revision 64053. Thanks, John.

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kd-tree
by Kraus Philipp 16 Feb '11

16 Feb '11

Hello, is there a kd-tree implementation with the ublas structures within the boost? I have some vectors and need a kd-tree to organize them. Thanks Phil

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Re: [Boost-users] Building boost on Visual Studio
by John Drescher 15 Feb '11

15 Feb '11

On Tue, Feb 15, 2011 at 4:22 PM, Tyler Weston <tyler.weston(a)gmail.com> wrote: > --toolset=msvc-9.0 > Excellent. That is working. Thanks John

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Building boost on Visual Studio
by John Drescher 15 Feb '11

15 Feb '11

I opened a 32 bit Visual Studio 2008 command prompt to the location of the boost-1.45.0 source then ran the bootstrap batch file to create bjam. After this I executed the following command to build boost. bjam --build-dir="X:\32Bit\VC.90\Libraries\boost-1.45.0" toolset=msvc --build-type=complete stage it appears that boost built successfully however it named them vc100 instead of vc90. I do not have Visual Studio 2010 installed on my machine. I never had it installed. Anyways to use these in the framework that I will be using them in I need the names to be correct. Is there any way to force bjam to use the correct visual studio version when it names the libraries? Thanks in Advance, John M. Drescher

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shared_ptr failure with undefined type (msvc)
by Gennadiy Rozental 15 Feb '11

15 Feb '11

Hi, I came to expect shared_ptr to handle undefined type, but here I got a test case (simplified from my use case) where it's actually breaks under msvc and works under gcc: #include "boost/shared_ptr.hpp" class UndefinedType; //// base class for template class FooBase{ public: virtual ~FooBase(); virtual void fff(); }; template <typename T> class Foo: public FooBase { public: virtual void fff() { // any virtual implementations seen are [have to be able to be] instantiated. This fails unless T is visible. x.reset(x.get()); } private: boost::shared_ptr<T> x; }; //// now use Foo as a field in a class class User { Foo<UndefinedType> y; }; It fails with: ...\boost-1.39\boost/checked_delete.hpp(32) : error C2027: use of undefined type 'UndefinedType' Is this expected to compile? Is this MSVC issue? Gennadiy

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[Proto] Compiles under 1.42 but not under 1.44
by Hossein Haeri 15 Feb '11

15 Feb '11

Dear all, I have a piece of code that compiles under the Proto of Boost 1.42 but doesn't compile under that of Boost 1.44! The error messages that I get under 1.44 can be found in the PS. Any idea there? TIA,--Hossein P.S. Compiling: main.cpp main.cpp: In function 'int main()': main.cpp:73:3: error: no match for 'operator>>' in 'EW1<InpPool, GameState, KillMsg>() >> plus1' main.cpp:73:3: error: template argument 1 is invalid main.cpp:73:3: error: invalid type in declaration before ';' token main.cpp:73:3: error: no match for 'operator>>' in 'EW1<InpPool, GameState, KillMsg>() >> plus1' main.cpp:73:3: error: template argument 1 is invalid main.cpp:73:3: error: invalid type in declaration before '(' token main.cpp:73:3: error: no match for 'operator>>' in 'EW1<InpPool, GameState, KillMsg>() >> plus1' main.cpp:81:14: error: request for member 'value' in 'e1', which is of non-class type 'int'

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