December 2017 - Boost-users

(Newbie) Embedded programming, memory pools, and allocate_shared()
by Steven Boswell II 13 Dec '17

13 Dec '17

I apologize for bothering the mailing-list with this newbie question, but after searching the Net for several days, I still can't find the answers I'm looking for. I am considering using Boost for a project I'm doing on an embedded system.I can't seem to find a lot of discussion on the particulars of Boost in embedded systems, just a few here and there.The biggest relevant limitation in embedded programming is on dynamic memory allocation -- the usual pattern is to allocate all necessary memory in "startup" phases, e.g. launching the program, loading the next playing-field in a game application, etc. I believe I can do what I want with allocate_shared() and fixed-size memory pools.The first big issue I have is trying to figure out the size of the objects that'll be allocated from the pool.I don't want to just allocate a raw block of memory; I want to allocate a block with space for a certain number of objects of a homogeneous type.But an object_pool for a type T doesn't accurately reflect what allocate_shared() is going to try to create.From much digging around, it looks like it's actually creating a subclass of boost::detail::sp_counted_base, e.g. boost::detail::sp_counted_impl_pd<P,D>, boost::detail::sp_counted_impl_pda<P,D,A>, etc.It seems like I'm not supposed to refer to that class directly, but I don't know how else to get the size of individual objects for my pool-allocator.Also, navigating all the template-parameters needed by these classes is proving to be mind-twisting. Probably just because I'm seeing it for the first time. Another example of where I need to track down the implementation class is with async-operation handlers in Boost::ASIO, e.g. completion handlers for socket's async_read_some(), generic handlers passed to io_service::post(), and so on. In the case of socket::async_read_some(), there's an example in boost/doc/html/boost_asio/example/cpp03/allocation/server.cpp which shows how to allocate completion-handlers from a pool, but not how to get the size of the necessary completion-handler class. It appears the class is boost::asio::detail::reactive_socket_recv_op<>. Again, this doesn't seem to be a public class, nor can I find a nice public typedef for it. Can anyone advise me on how to use Boost in this way?All of the Boost memory-pools I've seen so far either just allocate chunks of raw memory, or they allocate non-shared variants of objects.A memory-pool with a given number of spaces for the final object type seems like a defensible, traditional solution, but it doesn't seem that Boost makes that easy.Am I way off base here? Thanks for any help. -Steven

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[thread] clock_gettime warning on OS X
by James Walker 13 Dec '17

13 Dec '17

I'm getting a warning in the file boost/thread/pthread/timespec.hpp pointing out that clock_gettime is only available on macOS 10.12 and later. This code is being compiled on macOS 10.13, but should be compatible with macOS versions back to 10.7. How can I fix it? Maybe change the setting of BOOST_THREAD_USEFIXES_TIMESPEC, which I don't see any documentation for?

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[SmartPtr] local_weak_ptr?
by Rob Conde 11 Dec '17

11 Dec '17

How are boost::local_shared_ptr and boost::weak_ptr intended to be used together? I expected a local_weak_ptr, but it's not there so I'm wondering how you would (correctly) use local_shared_ptr and weak_ptr, or if you need local_weak_ptr and this is just still on the TODO list? Thanks, Rob Conde

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boost::container::string: ambiguous overload for 'operator!='
by niXman 10 Dec '17

10 Dec '17

Hi, using gcc-7.2 in C++17 mode and boost-1.65.1 I get the "ambiguous overload for 'operator!='" error: test here: http://coliru.stacked-crooked.com/a/3fd8fb94c0d1aec2 the same error for 'operator==' -- Regards, niXman ___________________________________________________ Work for Bitcoins ___________________________________________________ Dual-target(32 & 64-bit) MinGW-W64 compilers for 32 and 64-bit Windows: https://sf.net/p/mingw-w64/

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[release] Boost 1.66.0 Release Candidate 1
by Daniel James 09 Dec '17

09 Dec '17

The release candidates for the 1.66.0 release are now available at: <https://dl.bintray.com/boostorg/release/1.66.0/source/> The in progress release notes are: <http://www.boost.org/users/history/in_progress.html> Library documentation is available at: <http://www.boost.org/doc/libs/1_66_0/> The SHA256 checksums are as follows: c9d29486dd12f19d321da65eb5f0a157ec0f0edfd4701ade48c644310c8f0676 boost_1_66_0_rc1.7z 6232f7e7873b2d1f112fb62c726f7066e9a7e0643ed2aac7d31d20bf5749fbc0 boost_1_66_0_rc1.tar.bz2 30ad6d1c7380d6e6a87ce1bc54388ab957de67a2e8fa44dd3c106eafad0f6ac2 boost_1_66_0_rc1.tar.gz cd2c64f243c89e04329e94f3b803f0744171b44fee7a8b4e3256b3a625dcbd1c boost_1_66_0_rc1.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy.

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Errors while trying to build boost::priority_queue
by Ram 09 Dec '17

09 Dec '17

Hi, When I try to build "priority_queue_example.cpp" it get these warnings(and so errors) pointing to "priority_queue_example.h" on the line where my priority_queue is declared. The warnings are, 1> priority_queue_example.cpp 1>c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(102): error C2220: warning treated as error - no 'object' file generated 1>c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(102): warning C4100: 'rhs' : unreferenced formal parameter 1> c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(102) : while compiling class template member function 'boost::heap::detail::size_holder<false,size_t>::size_holder(const boost::heap::detail::size_holder<false,size_t> &)' 1> c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(189) : see reference to function template instantiation 'boost::heap::detail::size_holder<false,size_t>::size_holder(const boost::heap::detail::size_holder<false,size_t> &)' being compiled 1> c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(151) : see reference to class template instantiation 'boost::heap::detail::size_holder<false,size_t>' being compiled 1> c:\Projects\lib\boost\boost\heap\priority_queue.hpp(65) : see reference to class template instantiation 'boost::heap::detail::heap_base<T,myObjectPtrCompare,false,unsigned __int64,false>' being compiled 1> with 1> [ 1> T=myObject * 1> ] 1> c:\Projects\priority_queue_example.h(193) : see reference to class template instantiation 'boost::heap::priority_queue<myObject *,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_>' being compiledcompare<ObjectPtrCompare>,boost::parameter::void_,boost::parameter::void My priority_queue is declared as, mutable boost::heap::priority_queue<myObject*, boost::heap::compare<myObjectPtrCompare> > hp; Can you please help me fix this, I have been trying to for 2 days. Not sure what this means. This is my comparison class defined, struct myObjectPtrCompare { bool operator()(const myObject* lhs, const myObject* rhs) const { return (lhs->getProp() < rhs->getProp()); } }; Thanks!

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boost::priority_queue help
by Ram 09 Dec '17

09 Dec '17

Created a boost::priority_queue with my comparison operation defined. Here is how my priority_queue looks, boost::heap::priority_queue<myObject*, boost::heap::compare<myObjectPtrCompare> > max_heap; My comparison is defined as, struct myObjectPtrCompare{ bool operator()(const myObject* lhs, const myObject* rhs) const { return (lhs->getTime() < rhs->getTime()); }}; I have used it as, myObject* obj1 = static_cast<myObject*>(base1); 'base1' is an object of class 'myBase'(base class of myObject) myObject and getTime() within it used for comparision are defined as, class myObject : public myBase { Time getTime() const { return time; }... ...} Compiling this gives me this error, c:\Projects\pq_test.cpp(27): error C2662: 'void boost::heap::priority_queue<myObject*,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_>::push(myObject *const &)' : cannot convert 'this' pointer from 'const boost::heap::priority_queue<myObject *,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_>' to 'boost::heap::priority_queue<myObject *,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_> &'1> Conversion loses qualifiers Using Visual Studio 2013 C++. I understand that I am doing something wrong with const correctness, but I am not able to figure out what is wrong. Any help is appreciated. TIA!

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boost::priority_queue const correctness problem, help needed
by Ram 08 Dec '17

08 Dec '17

Created a boost::priority_queue with my comparison operation defined. Here is how my priority_queue looks, boost::heap::priority_queue<myObject*, boost::heap::compare<myObjectPtrCompare> > max_heap; boost::heap::priority_queue<myObject*, boost::heap::compare<myObjectPtrCompare> > max_heap; My comparison is defined as, struct myObjectPtrCompare { bool operator()(const myObject* lhs, const myObject* rhs) const { return (lhs->getTime() < rhs->getTime()); } }; I have used it as, myObject* obj1 = static_cast<myObject*>(base1); 'base1' is an object of class 'myBase'(base class of myObject) myObject and getTime() within it used for comparision are defined as, class myObject : public myBase { Time getTime() const { return time; } .... } Compiling this gives me this error, c:\Projects\pq_test.cpp(27): error C2662: 'void boost::heap::priority_queue<myObject*,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_>::push(myObject *const &)' : cannot convert 'this' pointer from 'const boost::heap::priority_queue<myObject *,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_>' to 'boost::heap::priority_queue<myObject *,boost::heap::compare<myObjectPtrCompare>,boost::parameter::void_,boost::parameter::void_,boost::parameter::void_> &' 1> Conversion loses qualifiers Using Visual Studio 2013 C++. I understand that I am doing something wrong with const correctness, but I am not able to figure out what is wrong. Any help is appreciated. TIA!

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boost.test fails to zip custom datasets
by Georgios Sermaidis 08 Dec '17

08 Dec '17

I am trying to understand how to use datasets with the boost.test library. I am following the documentation here <http://www.boost.org/doc/libs/1_65_1/libs/test/doc/html/boost_test/tests_or…> and have created my dataset as follows: namespace bdata = boost::unit_test::data; struct test_set { class iterator { int m_a; public: iterator() : m_a(0){} void operator++() { ++m_a; } int operator*() const { return m_a; } }; using sample = int; enum {arity = 1}; auto begin() const { return iterator{}; } bdata::size_t size() const { return 5; // let's assume only 5 numbers } }; namespace boost { namespace unit_test { namespace data { namespace monomorphic { template <> struct is_dataset<test_set> : std::true_type{}; }}}} which is very simple and iterates numbers from 0 to 4. The following simple test compiles and runs just fine: // this works as expected and prints 0, 1, 2, 3, 4 BOOST_DATA_TEST_CASE( example_test1, test_set(), my_datum) { std::cout << my_datum << std::endl; } However, when I try to zip <http://www.boost.org/doc/libs/1_65_1/libs/test/doc/html/boost_test/tests_or…> two such datasets it fails to compile (Apple LLVM version 9.0.0 (clang-900.0.38)): // error: invalid operands to binary expression ('typename data::result_of::make<test_set>::type' (aka 'test_set') and 'test_set') test_set() ^ test_set(), // ~~~~~~~~~~~^~~~~~~~~~~~~ BOOST_DATA_TEST_CASE( example_test2, test_set() ^ test_set(), my_datum1, my_datum2) { std::cout << my_datum1 << " " << my_datum2 << std::endl; } Is what I am trying to do legal? If so, what is the correct way to achieve it? Thank you for your help! Live code here <https://wandbox.org/permlink/6CI286mynvVCjQdW>

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Easy install doesn't
by Jean-Louis Leroy 07 Dec '17

07 Dec '17

I downloaded the current version of boost from here: http://www.boost.org/users/download/ (the Unix tgz) Then I religiously followed these instructions: http://www.boost.org/doc/libs/1_61_0/more/getting_started/unix-variants.htm… It didn't install much of anything useful...just stuff in /usr/local/share/boost-build, apparently the build system. No headers were installed, no libs were built or installed... I tried to install from debian packages and that failed miserably too but that's another story... Help please?

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