- Boost - lists.boost.org

[Circular Buffer] Partial thread-safety
by Lasse Kärkkäinen 26 Nov '08

26 Nov '08

It would be very helpful if this container provided lock-free thread-safe implementation of concurrent reads and writes by two threads (producer-consumer), as such function is often needed where ring buffers are used. A prime example of that being receiving audio from a callback (possibly a signal handler), where the callback must not be blocked in any circumstances (meaning that it cannot wait for a lock). As this is a rather common use case, the realtime audio processing framework JACK actually implements such lock-free ring buffer: http://jackit.sourceforge.net/cgi-bin/lxr/http/source/libjack/ringbuffer.c Is there any reason why Boost.circular_buffer should not also implement this kind of thread-safety?

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accepted libraries for boost
by Hansi 26 Nov '08

26 Nov '08

Hello, I have one question regarding to the accepted libraries for boost. At the moment are a lot of libraries accepted which don't get the way to the released version of boost... is it not possible at least that there is one and only one place where the last version of the library is saved? At the moment it is really hard to find this last version.. Best regards Hansjörg

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[intrusive] constant/non-constant time size lists
by Kevin Sopp 26 Nov '08

26 Nov '08

Hi Ion, have you thought about instantiating two different interfaces for constant and non-constant time size() lists respectively? Instead of instantiating one interface that has differing complexity guarantees and is restricted by the lowest common denominator of what is possible with constant-time size(). Non-constant time size() lists would allow to implement higher level functionality as static member functions or as non-member functions, and some functionality like splicing needs no additional list& parameter. If I had such a list I could make my functions work on iterator ranges without the need to pass the list object along. So what I need is access to the nodes so that I can call circular_list_algorithms directly on these. I don't see an easy way to achieve that goal right now. As far as I can tell I need to use the undocumented list_iterator::pointed_node() function - which is okay, I'm only hesitant because it is undocumented. I'm willing to change my code if that interface ever changes though. Kevin

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[UUID] seed_rng on Windows
by Kaj Björklund 26 Nov '08

26 Nov '08

Hi all, It would be nice if seed_rng used CryptGenRandom (or something similar) on Windows instead of trying to open /dev/urandom. The patch for seed_rng.hpp at: http://www.dynaroad.com/win.diff tries to use CryptGenRandom when BOOST_WINDOWS and _WINDOWS_ (i.e. windows.h has been included before uuid.hpp) are defined. This seems to work on Windows XP SP2 and Visual Studio 2005. Cheers, -kaj

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Support for std::nested_exception in Boost.Exception?
by Chris Newbold 26 Nov '08

26 Nov '08

Are there any plans (or any desire) for supporting the nested exception functionality (N2559) now in the C++0x draft in the Boost.Exception library? -Chris

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Using boost::filesystem with TCHAR
by Rob Caldecott 25 Nov '08

25 Nov '08

I wish to use the boost::filesystem library with some Windows apps and want to define TCHAR-friendly types. I *think* the following code should do the trick, giving me a boost::filesystem::tpath type, but is there anything I've missed? tpath.hpp #include <boost/filesystem.hpp> namespace boost { namespace filesystem { struct tpath_traits; typedef basic_path<std::basic_string<TCHAR>, tpath_traits> tpath; struct tpath_traits { typedef std::basic_string<TCHAR> internal_string_type; typedef std::basic_string<TCHAR> external_string_type; static external_string_type to_external( const tpath &, const internal_string_type & src ) { return src; } static internal_string_type to_internal( const external_string_type & src ) { return src; } }; } // filesystem } // boost

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Building 'stage' by default
by Vladimir Prus 25 Nov '08

25 Nov '08

We presently have 3 ways of building C++ Boost from top-level directory: - with 'stage' target -- only libraries are installed - with 'install' target -- both libraries and headers are installed - with no explicit target -- everything is built, but nothing installed It seems to me that the first two options are what the majority of users will want, so some of them should be the default. I have a local patch that makes 'stage' the default, and additionally prints the following message: Performing 'stage' build by default: - binaries installed into 'stage/lib' - headers not installed, use the source tree Use the 'install' target for complete installation. This message is printed only if no explicit target is specified -- if user types 'stage' or 'install', it's assumed he knows what he's doing. Anybody has any comments on this change in defaults, or about the wording of the message? Thanks, Volodya -- Vladimir Prus http://vladimir_prus.blogspot.com Boost.Build V2: http://boost.org/boost-build2

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Boost version meaning
by vicente.botet 25 Nov '08

25 Nov '08

Hi, I would like to know what is the meaning of the 3 numbers on the Boost version X.Y.Z. When X changes, i.e. when we could have a Boost version 2.0.0 Which number means a complete rewriten? Which number means an incompatible evolution? Which number means new functions? Which number means major bugs corrections? Which number means only minor bugs corrections? Is this written somewhere? If we were to version individual Boost libraries which will be the apropiated schema? Should all the libraries follow the same schema? What do you think of? X: complete rewriten or incompatible evolution Y: new functions or major bugs corrections Z: minor bugs corrections Thanks, Vicente

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Strange snippet around operator T()
by Joel Falcou 24 Nov '08

24 Nov '08

I was trying to find some decent way to declare named constants in my code and ended up with the following snippet : struct const_one { typedef int type; const_one() {} template<class T> const_one(T const& ) {} template<class T> operator type() const { static type const v = {1}; return v; } template<class T> operator T() const { static T const v = {1}; return v; } }; static const const_one one_; This allow me to have the following behavior : int k = one_; float e = one_; and have proper transtyping taking place when needed. Turning this into a macro allow to declare a large sample of named constant that auto-transtype them when needed. Now funny thing is that this structure allow me to do stuff like : float k = one_ / ( 1. + three_); Now if I remove the operator type(), I can't. But if i add a printf statement in this one, it is never called. Do someone has a clue about this behavior or am I playing with some undefined behavior ? TIA -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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Re: [boost] dynamic_cast with WeakPtr?
by Sören Freudiger 24 Nov '08

24 Nov '08

ups, sorry, my fault.. the example seems to work, but I run into that problem because I tried to perform an dynamic_cast on that weak_ptr. How this should be done in this simple example? class Base { public: boost::weak_ptr<Base> neigh; }; class Derived : public Base { }; int main() { { boost::shared_ptr<Base> a(new Base); boost::shared_ptr<Derived> d(new Derived); a->neigh = d; d->neigh = a; //like that? boost::shared_ptr<Derived> pD2 = boost::shared_dynamic_cast< Derived >( a->neigh.lock()); } } -----Ursprüngliche Nachricht----- Von: Sören Freudiger [mailto:muffmolch@gmx.de] Gesendet: Montag, 24. November 2008 21:03 An: boost(a)lists.boost.org Betreff: dynamic_cast with WeakPtr? Hi @all Maybe you can help me. I tried to use weak_ptr for breaking circular references, but I found out that this pointers can't handle derived classes. But in my classes I have some neighbor relations that I want to tore with shared_ptr: class Base { public: boost::shared_ptr<Base> neigh; }; class Derived : public Base { }; int main() { { boost::shared_ptr<Base> a(new Base); boost::shared_ptr<Derived> d(new Derived) a.neigh = d; d.neigh = a; } //both objects are in memory because of circular references, but weak pointer doesn't work, //becaus eit seems to be unable handling derived classes... and there's no dynamic cast } How do you solve problems like that with boost pointers avoiding circular references? Best reagrds, SirAnn

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