July 2010 - Boost-users - lists.boost.org

enumeration type in boost
by archie14 27 Jul '10

27 Jul '10

Is there any support for proper usage of enumerations in any of the boost libraries? I am looking for something similar to Qt's QFlags class but can't find anything similar in boost.

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[Intrusive] problem with inheritance
by Stephen Schleimer 27 Jul '10

27 Jul '10

Folk, I have an object which serves as a header to a "page" of memory which I serialize by simply writing out. I deserialize by reading the page and then doing a bit of fixup. I do this for performance (no copies other than the I/O in both directions). The header has an intrusive list pointer. When I reload the page, I must clear the header from the intrusive list. The page has been relocated (it may not be in the same physical location as it was when it was written). Thus, a simple unlink does not work. I was unable to figure out how to re-init the pointer when I had a base_hook. So, I switched to a member hook supposing that I could simply clear the contents of the hook (violating the abstraction) on the reload. Unfortunately, the headers are members of a hierarchy. The member_hook is defined in the base class and it is used in a subclass. I abstracted the problem into the following code: #include <boost/intrusive/list.hpp> class Foo { public: boost::intrusive::list_member_hook<> hook_; }; class Bar : public Foo { public: int x; }; class BigMess { typedef boost::intrusive::member_hook<Bar, boost::intrusive::list_member_hook<>, &Bar::hook_> mho; typedef boost::intrusive::list<Bar, mho> BarList; BarList list; }; This fails to compile using g++ (GCC) 4.4.0 on centos 2.6.18-128.1.16.el5 with: foo.cpp:15: error: could not convert template argument ‘&Foo::hook_’ to ‘boost::intrusive::list_member_hook<> Bar::*’ Clearly, the type of the base class is taken to not be compatible with the subclass. It is not clear why, however. Any thoughts would be appreciated as to how to either fix the inheritance problem or how to clear the base_hook case (which does compile and runs, by the way :-) Thanks -steve

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Intrusive feature idea - accessor_hook
by Hite, Christopher 27 Jul '10

27 Jul '10

Intrusive has base_hooks and member_hooks. I wish it had a accessor hook, where you can define a member function which returns the a hook reference. My use case: I have a class being used between two threads and I want to break it up to avoid cache thrashing. struct Object{ struct UpdatedState{ } *updatedState; struct PrivateState{ } *privateState; struct PublishedState{ } *publishedState; }; So the users's thread updates stuff in UpdatedState and flags it for consumption by the service thread. The service thread has lots of private data associated with the object. It updates the user asychronously updating publishedState and flagging it for consumption by the user. The a nice way to flag things for consumption is to put them in an slist. The problem is that everyone wants an slist of Object instead of just a child like UpdatedState. The problem of course is that putting the hooks in Object would cause the cache trashing we were trying to avoid. Putting the hooks in the child objects requires a way back to Object. As work around a pointer could be added for each child back to Object. If I were writing my own linked lists, the solution is obvoius: I would add a field Object* nextUpdated to UpdatedState. What I propose is adding a accessor to Object list_member_hook<>& getUpdatedHook(); typedef accessor_hook<Object, list_member_hook<>, &Object::getUpdatedHook> MemberHookOption; Another advantage to allowing an accessor to be used is that the user can share memory between unused hooks by putting them in variant or union. In my case I've got 6 sorts 2 for add/change/delete prioritization. I only ever use 2 of these at a time, but I can't avoid the memory cost for having all the hooks. Chris Hite

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Failure to load boost libraries on Linux
by David Aldrich 27 Jul '10

27 Jul '10

Hi Please will some one help me with what is probably a simple Linux error? I have installed Boost 1.40 on Centos 5.3 using an rpm from blackopsoft.com. When I run my executable I get: Failed to load the following library files: [snip] dlerror = libboost_python.so.2: cannot open shared object file: No such file or directory Executing: /sbin/ldconfig -p | grep boost gives: libboost_python-mt.so.1.40.0 (libc6,x86-64) => /usr/lib64/libboost_python-mt.so.1.40.0 libboost_python-mt.so (libc6,x86-64) => /usr/lib64/libboost_python-mt.so libboost_python-mt-d.so.1.40.0 (libc6,x86-64) => /usr/lib64/libboost_python-mt-d.so.1.40.0 libboost_python-mt-d.so (libc6,x86-64) => /usr/lib64/libboost_python-mt-d.so Please can anyone suggest what is wrong? Best regards David

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[bind][function] Do copy constructors invoked inside boost::bind / boost::function get optimized out?
by Steve Lorimer 27 Jul '10

27 Jul '10

Hi I'm using boost::bind to convert a function of the form: T::fun(boost::intrusive_ptr<U>) into a form which can be stored by boost::function. Outputting calls to intrusive_ptr_add_ref and intrusive_ptr_release reveals there are a massive number of copies of the intrusive_ptr. For a single call of boost::bind on a I'm wondering what kind of overhead this will add if I'm calling boost::bind on boost::intrusive_ptr a LOT of times? Will the copies be optimized out? There are 6 calls to intrusive_ptr_add_ref when calling boost::bind to bind a member function pointer to an object which is wrapped up in an intrusive_ptr There are 5 calls to intrusive_ptr_add_ref when calling boost::bind to bind an argument which is an intrusive_ptr There are 12 calls to intrusive_ptr_add_ref when using boost::function to store the result of boost::bind when called to bind a member function pointer to an object which is wrapped up in an intrusive_ptr There are 11 calls to intrusive_ptr_add_ref when using boost::function to store the result of boost::bind when called to bind an argument which is an intrusive_ptr Example code and output showing the calls below: #include <iostream> #include <boost/intrusive_ptr.hpp> #include <boost/function.hpp> #include <boost/bind.hpp> using namespace std; struct ref_ctd { int refs; ref_ctd() : refs(0) { } }; template<typename T> void intrusive_ptr_add_ref(T* p) { cout << "++ setting p (" << p << ")'s refs to " << p->refs + 1 << endl; ++p->refs; } template<typename T> void intrusive_ptr_release(T* p) { cout << "-- setting p (" << p << ")'s refs to " << p->refs - 1 << endl; if (!--p->refs) delete p; } struct foo : public ref_ctd { void func(char a) { cout << a << endl; } }; void bar(boost::intrusive_ptr<foo> f) { f->func('b'); } int main() { cout << "--------- creating intrusive ptr ----------" << endl; boost::intrusive_ptr<foo> f(new foo); cout << "--------- binding intrusive_ptr object ----------" << endl; boost::bind(&foo::func, f, 'a'); cout << "--------- now storing result of bind ----------" << endl; boost::function<void()> func1 = boost::bind(&foo::func, f, 'a'); cout << "--------- binding intrusive_ptr object ----------" << endl; boost::bind(bar, f); cout << "--------- now storing result of bind ----------" << endl; boost::function<void()> func2 = boost::bind(bar, f); return 0; } Here are the results: --------- creating intrusive ptr ---------- ++ setting p (0x33b18)'s refs to 1 --------- binding intrusive_ptr object ---------- ++ setting p (0x33b18)'s refs to 2 ++ setting p (0x33b18)'s refs to 3 ++ setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 -- setting p (0x33b18)'s refs to 3 -- setting p (0x33b18)'s refs to 2 -- setting p (0x33b18)'s refs to 1 --------- now storing result of bind ---------- ++ setting p (0x33b18)'s refs to 2 ++ setting p (0x33b18)'s refs to 3 ++ setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 -- setting p (0x33b18)'s refs to 3 ++ setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 ++ setting p (0x33b18)'s refs to 7 ++ setting p (0x33b18)'s refs to 8 ++ setting p (0x33b18)'s refs to 9 -- setting p (0x33b18)'s refs to 8 -- setting p (0x33b18)'s refs to 7 -- setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 -- setting p (0x33b18)'s refs to 3 -- setting p (0x33b18)'s refs to 2 --------- binding intrusive_ptr object ---------- ++ setting p (0x33b18)'s refs to 3 ++ setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 -- setting p (0x33b18)'s refs to 3 -- setting p (0x33b18)'s refs to 2 --------- now storing result of bind ---------- ++ setting p (0x33b18)'s refs to 3 ++ setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 ++ setting p (0x33b18)'s refs to 5 ++ setting p (0x33b18)'s refs to 6 ++ setting p (0x33b18)'s refs to 7 ++ setting p (0x33b18)'s refs to 8 ++ setting p (0x33b18)'s refs to 9 ++ setting p (0x33b18)'s refs to 10 -- setting p (0x33b18)'s refs to 9 -- setting p (0x33b18)'s refs to 8 -- setting p (0x33b18)'s refs to 7 -- setting p (0x33b18)'s refs to 6 -- setting p (0x33b18)'s refs to 5 -- setting p (0x33b18)'s refs to 4 -- setting p (0x33b18)'s refs to 3 -- setting p (0x33b18)'s refs to 2 -- setting p (0x33b18)'s refs to 1 -- setting p (0x33b18)'s refs to 0

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BOOST_STATIC_ASSERT has different behavior on different platforms
by Alexander Vinokur 27 Jul '10

27 Jul '10

Hi, BOOST_STATIC_ASSERT has different behavior on different platforms Boost 1.34 -------- File foo01. cpp -------- #include <boost/static_assert.hpp> struct Foo { int m_value; Foo(); }; Foo::Foo() { BOOST_STATIC_ASSERT(sizeof(this->m_value) == 4); } int main() { Foo f; return 0; } --------------------------------- No compilation errors on UNIX compilers HP: aCC: HP C/aC++ B3910B A.06.25.01 [May 16 2010] Sun: C++ 5.9 SunOS_sparc Patch 124863-01 2007/07/25 AIX: IBM XL C/C++ Enterprise Edition V8.0 for AIX; Version: 08.00.0000.0014 Linux: Intel(R) C++ Intel(R) 64 Compiler, Version 11.0 There are compilation errors on Windows compiler Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 14.00.50727.762 for 80x86 foo01.cpp foo01.cpp(11) : error C2355: 'this' : can only be referenced inside non-static member functions foo01.cpp(11) : error C2227: left of '->m_value' must point to class/struct/union/generic type foo01.cpp(11) : error C2027: use of undefined type 'boost::STATIC_ASSERTION_FAILURE' C:\ADJUST\3rdParties\boost_1_34_0\boost/static_assert.hpp(34) : see declaration of 'boost::STATIC_ASSERTION_FAILURE' Regards, Alex Vinokur This message and the information contained herein is proprietary and confidential and subject to the Amdocs policy statement, you may review at http://www.amdocs.com/email_disclaimer.asp

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Phoenix3 port to proto complete
by Thomas Heller 27 Jul '10

27 Jul '10

Ladies and Gentlemen, I proudly announce that the port of phoenix3 is completed! All testcases pass! (some with minor modifications) So, What is next? Here is my proposed schedule: - fix some minor issues - improve boost.bind compatibility: make all boost.bind testcases pass - implement all boost.lambda testcases and make them pass, as far as it is reasonable - add support for C++0x lambdas - make interoperability testcases for std::function, boost::function - adapt the documentation - clean up code (some parts are a little messy as of now) - improve compile time Did I miss something? This is a very tight schedule, I may not be able to finish all points during the GSoC period. Any help will be appreciated. Additionally a review of the current code is highly appreciated to point out some defects that might exist. The code can be checked out at: https://svn.boost.org/svn/boost/sandbox/SOC/2010/phoenix3 I will be happy to answer your questions! Additionally I would like to thank Joel de Guzman and Eric Niebler for their great assistance and initial designs! Best Regards, Thomas Heller

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query regarding mutex
by Abbhishek Misra 27 Jul '10

27 Jul '10

Hello All, This is how mutex class looks like #include <boost/thread/mutex.hpp> class mutex: boost::noncopyable { public: mutex(); ~mutex(); void lock(); bool try_lock(); void unlock(); typedef platform-specific-type native_handle_type; native_handle_type native_handle(); typedef unique_lock<mutex> scoped_lock; typedef unspecified-type scoped_try_lock; }; Please help me figure out what purpose does 'unspecified-type' serve below. typedef unspecified-type scoped_try_lock; as I understand typedef type_a name_a ; enables name_a to be used instead of type_a what does unspecified-type stand for ? and how does one use it ? regards Abhishek

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[Graph] Lazy BFS
by Belcourt, Kenneth 27 Jul '10

27 Jul '10

Hi, I'm looking to traverse a DAG using BFS where vertices are discovered after the last incident edge has been examined. That is, I want to discover vertices lazily rather than the current BFS behavior of discovering vertices eagerly (following the first incident edge). I know I can modify the BFS algorithm to effect this behavior but I'm wondering if anyone has figured out the visitor changes necessary to support this? Thanks. -- Noel

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boost MPI Signal: Segmentation fault (11)
by Jack Bryan 26 Jul '10

26 Jul '10

Dear All, I run a 6 parallel processes with boost MPI on a system with OpenMPI. When the run-time of the program is short, it works well. But, if the run-time is long, I got errors: [n124:45521] *** Process received signal ***[n124:45521] Signal: Segmentation fault (11)[n124:45521] Signal code: Address not mapped (1)[n124:45521] Failing at address: 0x44[n124:45521] [ 0] /lib64/libpthread.so.0 [0x3c50e0e4c0][n124:45521] [ 1] /lib64/libc.so.6(strlen+0x10) [0x3c50278d60][n124:45521] [ 2] /lib64/libc.so.6(_IO_vfprintf+0x4479) [0x3c50246b19][n124:45521] [ 3] /lib64/libc.so.6(_IO_printf+0x9a) [0x3c5024d3aa][n124:45521] [ 4] /home/path/exec [0x40ec9a][n124:45521] [ 5] /lib64/libc.so.6(__libc_start_main+0xf4) [0x3c5021d974][n124:45521] [ 6] /home/path/exec [0x401139][n124:45521] *** End of error message *** It seems that there may be some problems about memory management. But, I cannot find the reason. My program needs to write results to some files. If I open the files too many without closing them, I may get the above errors. But, I have removed the writing files from my program. The problem appears again when the program runs longer time. Any help is appreciated. Jack July 25 2010 _________________________________________________________________ The New Busy is not the too busy. Combine all your e-mail accounts with Hotmail. http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=PID28…

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