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[MPL] Proposal for runtime_contains_if algorithm submission
by Eldar Kononov 26 Apr '10

26 Apr '10

Hello everyone. Currently only one runtime algorithm is available in MPL: for_each. I suggest to add another one: runtime_contains_if. The problem is searching through the sequence of types and find that one which satisfies some runtime predicate. Sample task: Given some base abstract class: struct base { virtual ~base(){} }; The implementation of the base could be one of the following classes: struct child1 : public base {}; struct child2 : public base {}; struct child3 : public base {}; struct child4 : public base {}; struct child5 : public base {}; Now suppose you have "base* b" and you need to find out if its concrete type is either child3 or child4 (in practise the set of types to check could be larger). I propose the following solution: 1. You write a predicate similar to STL contains_if but with template type in operator(). The concept is the same as in boost::mpl::for_each. struct child_detector { base* base_; child_detector( base* b ) : base_( b ) {} template< typename Derived_ > bool operator()( Derived_* ) { return ( 0 != dynamic_cast< Derived_* >( base_ ) ); } }; 2. You use boost::mpl::runtime_contains_if algorithm: bool type_is_special( base* b ) { typedef boost::mpl::list< child3, child4 > special_types; return boost::mpl::runtime_contains_if< special_types >( child_detector(b) ); } The implementation of the boost::mpl::runtime_contains_if is in attached runtime_contains_if.hpp. Complete example is in attached runtime_contains_if_example.cpp.

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[Install] Am I doing something silly....?
by Robert Jones 26 Apr '10

26 Apr '10

Hi Guys Despite having used Boost for quite while I'm doing my first install of Boost on a Linux box and don't seem to be getting it right! This should be straight forward, using all the defaults. Specifically this is Fedora 11 (64-bit), with gcc 4.4.1 and Boost 1.42, and I don't have write permission for /usr/local, so... > ./bootstrap.sh --prefix=/home/rjones/thirdparty/boost/boost_1_42_0 .... > ./bjam install 2>&1 | tee bjam.log There's A LOT of noise, lots of warnings, some errors, and finally cp: cannot create regular file `/usr/local/lib/libboost_wave.a': Permission denied cp "bin.v2/libs/wave/build/gcc-4.4.1/release/link-static/threading-multi/libboost_wave.a" "/usr/local/lib/libboost_wave.a" ...failed common.copy /usr/local/lib/libboost_wave.a... ...failed updating 98 targets... ...skipped 7732 targets... ...updated 674 targets... I've attached the logfile begin and end (it's huge!). Can anyone tell me what I'm doing wrong. Thanks, Rob.

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Compiling specific modules
by Samuel Williams 26 Apr '10

26 Apr '10

Dear Friends, I'm sorry if this is a stupid question... however, I want to compile boost but only specific parts of it. Is this possible? I'm already using --build-type=minimal - but I want to compile libraries for exactly what I'm using so it doesn't take so long for cross platform compilation. Is there some documentation somewhere? Thanks, Samuel

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[1.43.0] Beta 1 now available from SourceForge
by Beman Dawes 25 Apr '10

25 Apr '10

Boost release 1.43.0 beta 1 is now available from SourceForge See http://sourceforge.net/projects/boost/files/ For details of what's in the release, see http://beta.boost.org/users/news/version_1_43_0. Note that the links to files on this web page are for the final release - use the SourceForge link above to get the beta files. There are known issues with GCC 4.5 and VC++ 2010. These compilers were released a few weeks ago so support is still rough around the edges. Some fixes will make it into the final 1.43.0 release, but full support will not be available until 1.44.0. Please download the beta, give it a try, and report any problems you encounter here. -- The Boost Release Team

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[BGL] Examples missing in the documentation
by Hossein Haeri 25 Apr '10

25 Apr '10

Dear all, I have noticed that the following two examples have are missing in the BGL online documentation: example/exterior_edge_properties.cpp example/bellman_ford.cpp (I spotted these in the following page: http://www.boost.org/doc/libs/1_42_0/libs/graph/doc/using_property_maps.html) Strangely enough, they apparently don't exist in the entire Boost website either (Google doesn't find them). Nor are they part of the 1.42 pack. Am I missing anything? TTFN, --Hossein

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phoenix function problem
by Olaf Peter 24 Apr '10

24 Apr '10

Hi, in the example attached, the 1st test case fails on runtime: test_phoenix_fcn.cpp(105): test 'at_c<0>( rlc ) && at_c<1>( rlc ) && at_c<2>( rlc )' failed in function 'int main(int, char**)' test_phoenix_fcn: /home/olaf/Projects/programming/cpp/boost/trunk/boost/optional/optional.hpp:591: typename boost::optional_detail::optional_base<T>::reference_type boost::optional<T>::get() [with T = double]: Assertion `this->is_initialized()' failed. Aborted the 2nd (with defined WANT_TO_HAVE) doesn't compile. This is the goal. Where is my misunderstanding here? To to get it working correctly? Thanks, Olaf

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Boost.Fusion compilation error gcc 4.4.3 in boost/fusion/include/make_unfused_generic.hpp
by Theo de Vries 24 Apr '10

24 Apr '10

I have an up-to-date Archlinux system with a standard gcc 4.4.3. I wish to use a library that in turn uses Boost.Fusion. I get compilation errors for Boost.Fusion 1.41 and 1.42 (version 1.40 and 1.37 are ok). Simple test program to reproduce: #include <boost/fusion/include/make_unfused_generic.hpp> #include <iostream> int main() { std::cout << "Hello world"; } The first error that I get is: boost/fusion/functional/adapter/unfused_generic.hpp:54 error: a function call cannot appear in a constant-expression boost/fusion/functional/adapter/unfused_generic.hpp:54 error: template argument 1 is invalid Google has not helped me to resolve my problems. Any help is greatly appreciated. Theo.

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shared_ptr
by mh00219＠surrey.ac.uk 23 Apr '10

23 Apr '10

Hello Please tell me how can base class pointer be assigned to derived class pointer? are they both same? if they then how? Please reply must. regrads Hammad

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Re: [Boost-users] Boost graph write_graphml
by Overmind DL1 23 Apr '10

23 Apr '10

On Fri, 23 Apr 2010, Theodore McCormack wrote: > I am having troubles figuring out how to use write_graphml from the > documentation. My problem is in creating the dynamic_property.ï¿œTo access > my vertex properties i use this:ï¿œ > > VERTEXPROPERTIES& properties(const Vertex& v) > { > typename property_map<GraphContainer, vertex_properties_t>::type param = get(vertex_properties, graph); > return param[v]; > } > whereï¿œVERTEXPROPERTIES is a type of a structure that i use for vertex properties. > > how would i go about creating a dynamic_property from that property map? dynamic_properties dp; dp.property("properties", param); A more complete example is at <URL:http://www.boost.org/doc/libs/1_42_0/libs/graph/doc/write_graphml.html>. Note that if you would like separate names for the different properties you will need to define separate property names and add an entry to dp for each; property maps can be created using a function call on an existing property map, though, so you would not need to rearrange your graph data structures. Are you using bundled properties by any chance? Or do you really have a single struct that has all of your properties but is not used as a bundle? -- Jeremiah Willcock

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Re: [Boost-users] Troubleshooing deadlock with upgrade_lock<shared_mutex>
by Ken Smith 23 Apr '10

23 Apr '10

Hmmm . . . actually, as I've been poking around, I think I've I found some more explanations elsewhere which, if I'm understanding them correctly, indicate that (a) I've misunderstood what an upgrade_lock does, but also that (b) my code shouldn't be subject to* *the deadlocks you're describing (though it's clearly susceptible to others :-). The key (which isn't clearly noted in the documentation) is that an upgrade_lock is like a unique_lock in that only one upgrade_lock can be held at a time. (I was thinking it was more like a shared_lock, in that multiple instances of it could be held at the same time, but Anthony Williams indicates that's not the case: http://groups.google.mv/group/boost-list/msg/2c93110e9e3dbb45.) This means that the behavior in my code could go something like: - transmit() acquires shared_lock. - createRoom() acquires upgrade_lock. - deleteRoom() attempts to acquire upgrade_lock and blocks (because of the upgrade_lock held by createRoom()). - createRoom() attempts to upgrade to a unique_lock and blocks (because of the shared_lock held by transmit()). - transmit() releases shared_lock. - createRoom() successfully upgrades to a unique_lock. (deleteRoom() is still blocked because createRoom() already has an upgrade_lock) - transmit() attempts to acquire shared_lock and blocks. - createRoom() releases unique lock. - deleteRoom() successfully acquires upgrade_lock. - transmit() successfully acquires shared_lock. - life goes on Now, if transmit() were regularly taking longer than 20 ms to complete, so that it was regularly being called reentrantly, I could imagine that it would build up a pretty good backlog of shared locks, which would prevent createRoom() and deleteRoom() from acquiring their *unique* locks. But if I'm understanding this correctly, I can't think of a scenario that would result in the behavior I'm seeing, i.e., both the createRoom() and deleteRoom() methods blocking each other while attempting to acquire an upgrade_lock. (Since no other unique or upgrade locks appear to be held elsewhere at the time.) That said, I'm reasonably new to multithreading, and I'm still having to think through these issues, so I might be missing something. (Actually, I clearly am, I'm just trying to figure out what it is :-). Ken Smith Cell: 425-443-2359 Email: smithkl42(a)gmail.com Blog: http://blog.wouldbetheologian.com/ On Fri, Apr 23, 2010 at 11:42 AM, Frank Mori Hess <frank.hess(a)nist.gov>wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On Friday 23 April 2010, Ken Smith wrote: > > On Fri, Apr 23, 2010 at 10:57 AM, Frank Mori Hess > > > Yes, they are deadlocked because both upgrade locks are waiting for the > > other to release shared ownership so they can upgrade to unique > ownership. > > > > Perhaps I wasn't clear. They're not waiting on the > upgrade_to_unique_lock > > lines, but on the upgrade_lock lines. > > Despite my initial misunderstanding, your code still appears to be > vulnerable > to the deadlock I described, even if that isn't what you are hitting at the > moment. > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (GNU/Linux) > > iEYEARECAAYFAkvR6i0ACgkQ5vihyNWuA4VNfQCfevtL72DQKITwIm8TaH3hk6z5 > TDAAnRyjfQVEitRqrlWtkzl/62EiG8Dc > =+p2O > -----END PGP SIGNATURE----- >

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