January 2011 - Boost-users - lists.preview.boost.org

[interprocess] Determine size of managed_shared_memory
by Kai Benndorf 12 Oct '19

12 Oct '19

Hi all, I want to create a managed_shared_memory in exactly the size I needed. Therefore I do something like this: size = sizeof( common_managed_shared_memory ); size += sizeof( MyClassInSharedMem ); managed_shared_memory segment(create_only, "name", size ); MyClassInSharedMem allocates itself some memory by segment->allocate(). I added this also to the size, but get a boost::interprocess::bad_alloc exception on allocating this additional memory. Are there some magic bytes I forgot to add? Many thanks in advance Kai

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[statechart] Passing parameters from event to State Local Storage
by Christophe Bourez 16 Nov '16

16 Nov '16

I need to maintain a parameter into the state local storage. This parameter is initially contained in the event that causes the transition to the target state. I give hereafter a small illustrative example. typename sc = boost::statechart; class EvTest : public sc::event<EvTest> { public: EvTest(std::size_t val) : value(val) {} std::size_t getValue() const { return this->value; } private: std::size_t value; }; class MyStateMachine; class StSource; class StTarget; class StSource : public sc::simple_state<StSource, MyStateMachine> { public: typedef sc::custom_reaction<EvTest> reactions; sc::result react(const EvTest &event) { // How to pass event.getValue() to the target state ? transit<StTarget>(); } }; class StTarget : public sc::simple_state<StTarget, MyStateMachine> { public: StTarget(std::size_t val) : val(value) {} private: std::size_t value; }; Thanks, Christophe

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Statechart serialization
by mbrodeur65 04 Mar '15

04 Mar '15

Hi, I'm looking for a solution to serialize boost::statechart objects. I'm aware that this feature is on the statechart library todo list but was wondering if there are any workaround to achieve this with the latest boost release (1.34) ? thanks for your help ! mbrodeur65 -- View this message in context: http://www.nabble.com/Statechart-serialization-tf4131326.html#a11749139 Sent from the Boost - Users mailing list archive at Nabble.com.

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[Thread] Read-write locks
by lfrfly＠icqmail.com 18 Sep '14

18 Sep '14

I'm trying to create a standard read/write lock using Boost Threads, and I'm having a bit of difficulty mapping the Boost concepts onto the usual ones. A read/write lock should have several states: Locked for reading (multiple threads may lock at once), locked for writing (only one thread may lock, and no threads may be locked for reading at the same time), and unlocked. Ideally it would be nice if an RWL which is locked for reading may temporarily upgrade to locked for writing, then return to the locked for reading state. Boost supports several relevant notions of locking: shared locking, upgrade locking, and exclusive locking. This to me is a confusing distinction. In particular, a shared_mutex seems appropriate as the basis for a RWL, but is lock_upgrade() the equivalent of a write lock and lock_shared the equivalent of a read lock? This is unclear. If "upgrade locking" is not the same as "exclusive locking", then is an upgrade lock actually exclusive? Could someone please clarify this.

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[Statechart] How to decide between post_event and process_event atrun time ?
by Philippe DAVID 22 Jul '14

22 Jul '14

Hi, I have a method in which I want to post/process an event. The thing is, this method can be called from outside the state machine (so I need to call process_event), or indirectly by a reaction of the state machine (in this case I must call post_event since process_event is not reentrant). I don't want to write 2 distinct methods to do this (one that calls post, and the other process), I would much rather prefer adding a 'if' in my method that tells me if I have to call process_event or post_event (if I'm being called indirectly by the state machine or not). Is there a way to do this with statechart ? regards, Philippe

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[asio] resolver::cancel() problem
by Matthew Edwards 14 Mar '14

14 Mar '14

In my application (and a separate test program) it seems as though the cancel() function on the resolver does not work as intended. For async resolves, the cancel functionality should abort them immediately and pass an 'operation aborted' error code to the callback handler. In my tests, I will resolve an invalid domain (this causes the resolve to take a few seconds, to demonstrate the problem), sleep for 100ms, then call cancel on the resolver object. No cancelling actually occurs, and the callback is simply triggered after a few seconds with a "No host found" error code, not the expected operation aborted. Has anyone experienced this before, or know how I might be using the resolver incorrectly?

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[BGL] Having a cost function as weight map
by Maxime van Noppen 06 Sep '13

06 Sep '13

Hi, I can't find how to do this pretty basic thing : having a function instead of a field to compute the cost of edges for various path finding algorithms. I couldn't find the answer in the documentation and Google was of no help. Did I miss something obvious ? Example : ------------------- #include <boost/graph/dijkstra_shortest_paths.hpp> #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> struct my_edge { double cost() const { return cost_ * 2; } double cost_; }; struct my_node { }; int main() { typedef boost::adjacency_list< boost::vecS, boost::vecS, boost::directedS, my_node, my_edge > graph_t; typedef boost::graph_traits<graph_t>::vertex_descriptor vertex_t; graph_t graph; vertex_t v /*= ... */; using boost::weight_map; // Works : boost::dijkstra_shortest_paths(graph, v, weight_map(boost::get(&my_edge::cost_, graph))); // Doesn't compile : //boost::dijkstra_shortest_paths(graph, v, // weight_map(boost::get(&my_edge::cost, graph))); } ------------------- Thanks ! -- Maxime

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can't get first example in boost tutorial to work
by 7stud 11 Mar '13

11 Mar '13

I'm trying to install boost on mac osx 10.4.7. I followed the tutorial "Getting Started on Unix Variants" found here: http://www.boost.org/doc/libs/1_35_0/ more/getting_started/unix-variants.html Following the instructions in the tutorial, I installed boost in /usr/local as instructed, so my directory structure is: /usr/local/boost_1_34_1/boost But when I run the first example in the tutorial: #include <boost/lambda/lambda.hpp> #include <iostream> #include <iterator> #include <algorithm> int main() { using namespace boost::lambda; typedef std::istream_iterator<int> in; std::for_each(in(std::cin), in(), std::cout << (_1 * 3) << " " ); } I get the error(among others): error: boost/lambda/lambda.hpp: No such file or directory If I change the include path to: #include </user/local/boost_1_34_1/boost/lambda/lambda.hpp> I get the error(among others): error: boost/lambda/core.hpp: No such file or directory But core.hpp is in the lambda directory: /usr/local/boost_1_34_1/boost/lambda$ ls algorithm.hpp control_structures.hpp lambda.hpp bind.hpp core.hpp loops.hpp casts.hpp detail numeric.hpp closures.hpp exceptions.hpp switch.hpp construct.hpp if.hpp I'm using the Xcode 2.4 IDE to run my C++ programs. I also tried to execute the program from the command line with the original include path: #include <boost/lambda/lambda.hpp> but I get the same error: ~/2testing/dir1$ g++ prog1.cpp prog1.cpp:1:35: error: boost/lambda/lambda.hpp: No such file or directory prog1.cpp: In function 'int main()': prog1.cpp:8: error: 'boost' has not been declared prog1.cpp:8: error: expected namespace-name before ';' token prog1.cpp:8: error: '<type error>' is not a namespace prog1.cpp:11: error: '_1' was not declared in this scope I get the same errors again with the full include path: #include </user/local/boost_1_34_1/boost/lambda/lambda.hpp> $ g++ prog1.cpp In file included from prog1.cpp:1: /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:14:33: error: boost/lambda/core.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:21:52: error: boost/lambda/detail/operator_actions.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:22:61: error: boost/lambda/detail/operator_lambda_func_base.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:23:63: error: boost/lambda/detail/operator_return_type_traits.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:26:45: error: boost/lambda/detail/operators.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:30:46: error: boost/lambda/detail/member_ptr.hpp: No such file or directory prog1.cpp: In function 'int main()': prog1.cpp:8: error: 'boost' has not been declared prog1.cpp:8: error: expected namespace-name before ';' token prog1.cpp:8: error: '<type error>' is not a namespace prog1.cpp:11: error: '_1' was not declared in this scope What path should I be using? Or, should I set an environment variable somewhere?

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Re: [Boost-users] asio HTTP Server 3 example memory leak
by admin＠thefireflyproject.us 25 Aug '12

25 Aug '12

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[multi_array] operator= requires resize - why?
by Markus Werle 04 Jun '12

04 Jun '12

Hi! IMHO the behaviour of operator= for multi_array is a little bit broken. A lot of preconditions required: template <typename ConstMultiArray> multi_array_ref& operator=(const ConstMultiArray& other) { [...] // make sure the dimensions agree assert(other.num_dimensions() == this->num_dimensions()); assert(std::equal(other.shape(),other.shape()+this->num_dimensions(), this->shape())); Besides the fact that I get mad about asserts instead of exceptions (please change this to a way users may choose) why do we have such an odd behaviour here? >From page 1, line 3 of the docs I cite: "The interface design is in line with the precedent set by the C++ Standard Library containers" - this is not true for operator=, since std::<container>::operator= works fine for me all the time _without_ any resize. Could we please change the behaviour of multi_array::operator= to take care of resize where in need to? IMHO operator= should result in a true copy ignoring previous state. Markus

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Recommended mock framework to use with Boost?
by doug livesey 15 Mar '12

15 Mar '12

Hi -- I'm trying to learn to develop properly with C++ and Boost, and to that end am learning along with Boost.Test, as I'm a BDD coder in another language (Ruby) in my day job. I'm at the point, now, where my tests could really benefit from a mocking framework. There doesn't appear to be one in Boost (not documented, at least), so I wondered if anyone on the list could recommend a mocking framework that they use that works well with Boost.Test? Any and all advice gratefully received, Doug.

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[build] cannot specify different version of gcc
by Brodie Thiesfield 25 Aug '11

25 Aug '11

Hi, I'm trying to build boost on CentOS 5.5 using the /usr/bin/gcc44 compiler and I'm running into difficulties with documentation not fitting reality. How do I make this work? What I've tried... Note: I've removed /usr/bin/gcc and /usr/bin/g++ to force errors when gcc44 and g++44 are not used. Using ./bootstrap.sh Building Boost.Jam with toolset ... tools/jam/src/### ### No toolset specified. Please use --toolset option. Setting CC=/usr/bin/gcc44 and CXX=/usr/bin/g++44 (note that this won't work if gcc and g++ exist because then it will default to the gcc toolkit and not the gcc-4.4 toolkit that I want). This builds a number of things (looking at the bootstrap.log) but still gives the following error. Ignoring the error and calling ./bjam then fails. Building Boost.Jam with toolset ... tools/jam/src/### ### No toolset specified. Please use --toolset option. Using ./bootstrap.sh --toolset=gcc gives an error: unrecognized option: --toolset=gcc Using ./bootstrap.sh --with-toolset=gcc gives an error: Building Boost.Jam with toolset gcc... Failed to build Boost.Jam -> bootstrap.log shows that it is trying to build with gcc, which doesn't exist, therefore error. Using ./bootstrap.sh --with-toolset=gcc-4.4 gives an error: Building Boost.Jam with toolset gcc... Failed to build Boost.Jam -> bootstrap.log shows ### Unknown toolset: gcc-4.4 Creating ~/user-config.jam as: import toolset.using ; using gcc : 4.4 : g++44 ; export BOOST_USER_CONFIG=~/user-config.jam Then calling the same ./bootstrap.sh command lines above show no difference. How in the world do I get this thing to use /usr/bin/gcc44 and /usr/bin/g++44 to compile? I think that I'm going to have to create local links ./gcc -> /usr/bin/gcc44 and add the current directory to the path just to get this to build the way that I want it to. This seems crazy. Regards, Brodie

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MSVC Visualizers Update
by Filip Konvička 28 Jul '11

28 Jul '11

Hi all, I've just updated the Boost visualizers wiki page at https://svn.boost.org/trac/boost/wiki/DebuggerVisualizers I updated the visualizer for Boost.MultiIndex, which did not work since Boost 1.35. I also added new visualizers for Boost.DateTime (ptime and time_duration) and a simple boost::shared_ptr visualizer. The visualizers are available for checkout via SVN at https://svn.boost.org/svn/boost/sandbox/boost_docs/subprojects/DebuggerVisu… Cheers, Filip

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[multi-array] Extracting dimension information from a multi-array
by Ryan McConnehey 15 Jul '11

15 Jul '11

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Asio unhandled exception
by Łukasz Majewski 20 May '11

20 May '11

Hello, I created a server single thread async (linux) and clinet (win). Every time client is close while server is writing to the socket connected to this client exception appears: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error>>' what(): Transport endpoint is not connected Aborted and server is terminated. I dont know why this exception is unhandled. int main( int argc, char** argv ) { try { boost::asio::io_service io_service; quotation_server server( io_service ); while ( true ) { try { io_service.run(); } catch( ... ){} } } catch ( std::exception& e ) { LOG << e.what() << std::endl; } catch( ... ) { LOG << "Unexpected exception" << std::endl; } return 0; }

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Boost Install on Mac OS X using GCC
by Andrew 07 May '11

07 May '11

Hello, I'm trying to install boost on mac using the gcc compiler. I encounter these errors during installation for all libraries: "g++" -Wl,-R -Wl,"/System/Library/Frameworks/Python.framework/Versions/2.6/lib" -Wl,-R -Wl,"/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/config" -o "stage/lib/libboost_prg_exec_monitor.dylib" -Wl,-h -Wl,libboost_prg_exec_monitor.dylib -shared -Wl,--start-group "/Users/andrew/boost/boost/bin.v2/libs/test/build/gcc-4.2.1/release/threading-multi/execution_monitor.o" "/Users/andrew/boost/boost/bin.v2/libs/test/build/gcc-4.2.1/release/threading-multi/debug.o" "/Users/andrew/boost/boost/bin.v2/libs/test/build/gcc-4.2.1/release/threading-multi/cpp_main.o" -Wl,-Bstatic -Wl,-Bdynamic -Wl,--end-group ...failed gcc.link.dll stage/lib/libboost_prg_exec_monitor.dylib... gcc.link.dll stage/lib/libboost_unit_test_framework.dylib ld: unknown option: -R collect2: ld returned 1 exit status I have no experience at all using boost in mac, and it is necessary that I use gcc. I am wondering if anyone could point me to a solution regarding this. Thanks, Andrew

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distributed breadth first search doesn't work properly?
by Mattia Lambertini 04 May '11

04 May '11

Hi, i am new to boost and i'm using the PBGL to write a software that compute some graph analysis. I've installed boost 1.44.0 and openmpi 1.5 I tried to run the breadth first search example located in $BOOST_ROOT/libs/graph_parallel/example with the graph $BOOST_ROOT/libs/graph/test/weighted_graph.gr All went well since i figure out that the result is different if i run the algorithm with a different number of processors. Only with one processor the values are corrected. here's what happens: mpirun -np 1 ./breadth_first_search.out graph g { subgraph cluster_0 { label="p0"; n0[label=0]; n1[label=2]; n2[label=1]; n3[label=2]; n4[label=1]; } n0 -- n2; n1 -- n1; n1 -- n3; n1 -- n4; n2 -- n1; n2 -- n3; n3 -- n4; n4 -- n0; n4 -- n1; } --------------------- mpirun -np 2 ./breadth_first_search.out graph g { subgraph cluster_0 { label="p0"; n0[label=0]; n1[label=1]; n2[label=1]; } n0 -- n2; n1 -- n1; n1 -- n3; n1 -- n4; n2 -- n1; n2 -- n3; subgraph cluster_1 { label="p1"; n3[label=1]; n4[label=0]; } n3 -- n4; n4 -- n0; n4 -- n1; } Is that correct? From the doc i can't figure out why.. -- Cordiali saluti, Mattia Lambertini

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Request for conditional index feature in boost multi-index
by Gokulakannan Somasundaram 28 Apr '11

28 Apr '11

Hi, First of all thanks for the great library, which had reduced our development time by a lot. In boost multi-index, we currently have almost all the indexing concepts integrated. Hence i am requesting for a new feature called conditional indexes, where in an index/view inside multi-index will only index a portion of the entries inside the entire multi-index(Say something that satisfies a functor). This is in resemblance to the partial indexes in Postgresql. I feel that would provide elegant solutions to lot of issues without forming round about solutions. For example i have a requirement where in there are two sets of data with the same search criteria, but different eviction criteria Say i have two sets of data with same search condition, but one set needs a MRU(Most Recently Used) list of 100 and the other set requires a MRU of 200. Say the entry is like this class Student { int student_no; char sex; std::string address; }; The search criteria is student_no, but for sex='m', we need MRU of 200 and for sex='f', we need a MRU of 100. Now i have a solution where in i introduce a new ordered index to maintain ordering. For example the IndexSpecifierList will be something like this typedef multi_index_container< Student, indexed_by< ordered_unique< member<Student, int, &Student::student_no> >, ordered_unique< composite_key< member<Student, char, &Student::sex>, member<Student, int, &Student::sex_specific_student_counter> > > > > student_set Here i have to introduce a new counter called sex_specific_student_counter, and during the eviction time, i need a logn search. Insertion also involves a extra logn complexity. Now instead if i have two sequenced indexes (like mentioned in the MRU example) in the place of second ordered index, but both with a condition on indexing only a few items, this would have looked more elegant and with better performance. Thanks in advance, Gokul.

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[Asio] Socket Read/Write Thread-Safety
by Timothy Liang 06 Apr '11

06 Apr '11

Hi, I'm implementing a full-duplex protocol over TCP/IP using Boost.Asio. Multiple threads will be calling 'io_service::run_one()', so I have to serialize my completion handlers. Since I need to be reading and writing on a socket at the same time, can I use the 'boost::asio::async_read(...)' and 'boost::asio::async_write(...)' functions? The documentation states that these are implemented in terms of calls to the stream's async_read_some and async_write_some functions, and the 'basic_stream_socket' class isn't thread-safe. Thanks, Timothy

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vs 2010 can't find correct boost lib version?
by Li, Tieniu 30 Mar '11

30 Mar '11

I built boost with visual studio 2010. Libraries of *-vc100-* are generated correctly. When trying to using boost.thread, VS 2010 generated error message: can't find *-vc90-*.lib. Any idea and fixing? Thanks a lot.

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Re: [Boost-users] Collecting boost multi-index meta data
by Joaquin M Lopez Munoz 25 Mar '11

25 Mar '11

Gokulakannan Somasundaram <gokul007 <at> gmail.com> writes: > > > Hi, > Say i have a boost::tuple / MPL Sequence, on which i have > created a multi-index. Is it possible for me collect all the > attribute numbers on which i have declared the > IndexSpecifierList( the one passed as template parameter to > boost::multi_index::indexed_by ) ? Hi Gokul, I'm not sure I undersand your question. Have you taken a look at the index_type_list nested type? http://www.boost.org/libs/multi_index/doc/reference/multi_index_container.h… types >From this MPL sequence you can easily extract the list of key extractor types used for defining the multi_index_container, which hopefully is close to what you're after. Don't hesitate to elaborate a little more on your question and I'll see whether I can be more helpful. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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[BGL] Separating twin vertices
by Shaun Jackman 19 Mar '11

19 Mar '11

Hi, I have a directed graph where every vertex has a twin vertex. It is known ahead of time which pairs of vertices are twins. I want to remove as few vertices as possible from the graph such that no vertex and its twin is in the same connected component. Could someone suggest an appropriate algorithm? I've just started delving into the BGL. So far I'm suitably impressed! Cheers, Shaun

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[iostreams] restriction device/filter
by Borko Jandras 09 Mar '11

09 Mar '11

Hello, I'm looking at the implementation of the "restriction" device, from Boost.Iostreams library, which provides access to a subsequence of the original device. When it reaches the end of the input subsequence, the restriction device start performing read()'s of size zero on the original device. Shouldn't it be returning an end-of-sequence marker (EOF) instead? I am using a restriction device as source parameter for the iostreams::copy function and this always results in an infinite loop. Am I doing something wrong? Thanks! - Borko

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[GIL] gray pixel iterator in generic algorithm
by Curtis Gehman 17 Feb '11

17 Feb '11

I'm trying to use GIL pixel iterators in a generic STL-style algorithm. I'm primarily using GIL for the generic 2D iterators. And in my context, I'm only interested in grayscale images. The value_type associated with GIL iterators is a pixel type, which typically is an object representing multiple channels (e.g., colors). It makes sense that comparison operators (e.g., <) are not defined for general color pixel types. For grayscale images, however, it makes sense that common arithmetic and comparison operators would be defined for the pixel type. This seems to be the case for the 8-bit grayscale GIL type (gray8_view_t). The iterator's value_type appears to be seamlessly evaluated to an unsigned char, exactly as I would expect. When I try to use a float image view type, however, the same magic doesn't seem to happen. Below is some toy code that demonstrates the issue. When the last line is knocked out with "//", the code compiles. But with that second template instantiation (for floats) there, the compiler (gcc 4.2 and VC++2010) exits when it does not find an operator< for the iterator's value_type when instantiating for gray32fc_view_t. I suppose that I can roll my own less<iterator_traits<SrcView::x_iterator>::value_type> functors. But I just started using GIL, and I'm hoping that there is a simpler solution. Any ideas? #include <algorithm> #include <iterator> #include <vector> #include <boost/gil/gil_all.hpp> namespace g = boost::gil; using std::vector; using std::iterator_traits; template <typename SrcView> inline vector<typename iterator_traits<typename SrcView::x_iterator>::value_type> row_min(const SrcView& src) { typedef typename iterator_traits<typename SrcView::x_iterator>::value_type value_t; vector<value_t> result; for (int y = 0; y < src.height(); ++y) { result.push_back(*std::min_element(src.row_begin(y), src.row_end(y))); } return result; } // Explicit template instantiation // Works for gray8c_view_t. template vector<iterator_traits<g::gray8c_view_t::x_iterator>::value_type> row_min(const g::gray8c_view_t& src); // Compile error for gray32fc_view_t. // No operator< for iterator_traits<g::gray32fc_view_t::x_iterator>::value_type. template vector<iterator_traits<g::gray32fc_view_t::x_iterator>::value_type> row_min(const g::gray32fc_view_t& src);

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Thread changes from Boost 1.38 to 1.45
by Ven Tadipatri 08 Feb '11

08 Feb '11

Hi, We upgraded our project from using Boost 1.38 to Boost 1.45 but now seem to be having some thread issues. The error doesn't happen for every run, but occasionally the wait method in condition_variable_any fails. At other times the program seems to run into an infinite loop, presumably waiting for a lock that's never released. I looked at the changes in http://www.boost.org/doc/libs/1_45_0/doc/html/thread/changes.html but don't see what could be causing the error to occur only after upgrading to Boost 1.45. Has anyone else experienced their code breaking when upgrading to the latest version of Boost? Thanks, Ven

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