October 2010 - Boost - lists.preview.boost.org

[btree] build advice needed
by Phil Endecott 04 Oct '10

04 Oct '10

Dear Beman & others, At the risk of appearing ignorant and being told the RTM, can someone please help me to build btree? I am attempting to do this on a smallish ARM Linux box where building the whole of Boost is impractical (but which should otherwise be very similar to an x86 Linux system). So far: # apt-get install g++ (etc) # apt-get install boost-build # apt-get install bjam # apt-get install git $ git clone git://github.com/Beman/Boost-Btree btree $ cd btree/libs/btree/build $ bjam error: Could not find parent for project at '.' error: Did not find Jamfile or project-root.jam in any parent directory. As it says, there is no project-root.jam or Jamfile in any parent; this makes me think that perhaps it is expecting this to be part of a larger Boost tree. Or, maybe I just don't know the right incantations. What's the easiest way to go about this? If I do need to get other Boost source code, if there some git magic that will do it for me? Thanks, Phil.

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[thread] Memory leak in Boost.Thread?
by Denis Arnaud 03 Oct '10

03 Oct '10

Hello, a Fedora user has reported a potential memory leak in Boost.Thread (see https://bugzilla.redhat.com/show_bug.cgi?id=627875 for details), detected with Valgrind in (at least) versions 1.41.0 and 1.44.0. Following is a code snippet allowing to reproduce the issue: ==================================== #include <boost/thread.hpp> void someWork() { double a; for(int i= 0;i< 1000;i++) { a+=log((double)i); } } int main() { for(int i = 0; i< 10; ++i) { boost::thread_group pool; for(int j = 0; j< 100; ++j) { pool.create_thread(someWork); } pool.join_all(); } } ==================================== Then, following is Valgrind's report: ==================================== ==6442== Memcheck, a memory error detector ==6442== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al. ==6442== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info ==6442== Command: ./boost_leak ==6442== ==6442== ==6442== HEAP SUMMARY: ==6442== in use at exit: 8 bytes in 1 blocks ==6442== total heap usage: 5,967 allocs, 5,966 frees, 701,720 bytes allocated ==6442== ==6442== 8 bytes in 1 blocks are still reachable in loss record 1 of 1 ==6442== at 0x4C2615D: malloc (vg_replace_malloc.c:195) ==6442== by 0x4E3F989: boost::detail::get_once_per_thread_epoch() (in /usr/lib64/libboost_thread-mt.so.1.44.0) ==6442== by 0x4E39923: ??? (in /usr/lib64/libboost_thread-mt.so.1.44.0) ==6442== by 0x4E39BC8: boost::detail::get_current_thread_data() (in /usr/lib64/libboost_thread-mt.so.1.44.0) ==6442== by 0x4E3A528: boost::this_thread::interruption_enabled() (in /usr/lib64/libboost_thread-mt.so.1.44.0) ==6442== by 0x4E3A548: boost::this_thread::disable_interruption::disable_interruption() (in /usr/lib64/libboost_thread-mt.so.1.44.0) ==6442== by 0x404DC4: boost::shared_mutex::lock() (in /tmp/boost_leak) ==6442== by 0x40588D: boost::lock_guard<boost::shared_mutex>::lock_guard(boost::shared_mutex&) (in /tmp/boost_leak) ==6442== by 0x405DB5: boost::thread* boost::thread_group::create_thread<void (*)()>(void (*)()) (in /tmp/boost_leak) ==6442== by 0x403B91: main (in /tmp/boost_leak) ==6442== ==6442== LEAK SUMMARY: ==6442== definitely lost: 0 bytes in 0 blocks ==6442== indirectly lost: 0 bytes in 0 blocks ==6442== possibly lost: 0 bytes in 0 blocks ==6442== still reachable: 8 bytes in 1 blocks ==6442== suppressed: 0 bytes in 0 blocks ==6442== ==6442== For counts of detected and suppressed errors, rerun with: -v ==6442== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 6) ==================================== Is that really a memory leak? Kind Regards Denis

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[filesystem] Issue with replace_extension
by cheesy4poofs 02 Oct '10

02 Oct '10

I've recently switched all our code to filesystem v3 and added BOOST_FILESYSTEM_NO_DEPRECATE on our builds for good measure. One of the changes I had to fix was our use of change_extension(), which was modified to use the replace_extension() method. However, some of our code started failing and I tracked it down to this example: boost::filesystem::path p("C:\\database\\test\\filename"); p.replace_extension(".db"); std::cout << p.string() << std::endl; // OUTPUT - C:\database\test\filename.db p = "C:\\database.1\\test\\filename"; p.replace_extension(".db"); // bug? std::cout << p.string() << std::endl; // OUTPUT - C:\database.db As you can see, in the second example, it truncates the path and assumes the directory name "database.1" has the extension that needs replacing. change_extension() did not behave this way. Is this the expected behavior? Thanks, Scott

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[ratio] Mini-review of the proposed ratio library
by Beman Dawes 02 Oct '10

02 Oct '10

> The review of Vicente Botet' Ratio library starts October 2nd and lasts > until October 11th, 2010, unless an extension occurs. > > What is it? > ======== > Portable implementation of the C++0x Standard Library's compile-time > rational arithmetic working on C++03 and C++0x compilers. See the > current C++0x working draft at > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3126.pdf > - What is your evaluation of the design? The question is essentially moot since Vicente followed the C++0x standard library design. The real question is "Does Boost need a library that every standard library vendor will be supplying anyhow?" For me, the answer is, yes, at least provisionally. The provisional part is because the library I'd really like to see in Boost in chrono. But we can't have <boost/chrono.hpp> without <boost/ratio.hpp>, so I'm in favor of ratio. The reason I'd like a Boost version is that I don't want to have to wait years and years to be able to use <boost/chrono.hpp> and <boost/ratio.hpp> in Boost libraries. I want to be able to use them with the compilers and standard libraries people are using today, not years from now. > - What is your evaluation of the implementation? I am familiar with the original source code, and worked on boostifying it. Vicente has done a lot of work to make the code more robust in the Boost environment. > - What is your evaluation of the documentation? I skimmed through it, and checked the header against the C++ standard. My impression is favorable. > - What is your evaluation of the potential usefulness of the library? Chrono needs it:-) > - Did you try to use the library? With what compiler? Did you have any problems? No. > - How much effort did you put into your evaluation? A glance? A quick > - reading? In-depth study? A quick skim through the docs. > - Are you knowledgeable about the problem domain? Some knowledge, but far from an expert. > And finally, every review should answer this question: > > - Do you think the library should be accepted as a Boost library? Yes. I'm hoping others will post more in depth reviews. My review is really just a mini-review, but maybe will help to keep the ball rolling. --Beman

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Boost ABI compatibility analysis at linuxtesting.org
by Mateusz Loskot 02 Oct '10

02 Oct '10

Hi, I've searched the list archives and I don't find any posts referring to this interesting resource. The http://linuxtesting.org hosts reports of ABI analysi performed by ABI compatibility checker [1] tool against number of open source libraries [2]. Boost included [3]. [1] http://ispras.linux-foundation.org/index.php/ABI_compliance_checker [2] http://linuxtesting.org/upstream-tracker/index.html [3] http://linuxtesting.org/upstream-tracker/versions/boost.html Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org Member of ACCU, http://accu.org

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[boost::bind] How does it works for overloaded member functions in this example?
by Chaos A.D. 02 Oct '10

02 Oct '10

Hi there! Recently I was extremely surprised by the fact that boost::bind can handle the case of binding overloaded member functions! Here is the simplified testcase, which works fine in gcc 4.4.3. #include <boost/bind.hpp> struct Test { static void Func(int) {}; static void Func(int, const char*) {}; }; int main(int argc, char **argv) { boost::bind(&Test::Func, 5)(); boost::bind(&Test::Func, 5, "WORKS!")(); return 0; } In full testcase i tried to reproduce simplified boost::bind logic, and ensured, that my simplified version is still incorrect: #include <boost/bind.hpp> template <class A1> class Args1 { template <class Fn> void call(Fn fn) { fn(a1); } A1 a1; }; template <class A1, class A2> class Args2 { template <class Fn> void call(Fn fn) { fn(a1, a2); } A1 a1; A2 a2; }; template <class Fn, class Args> struct bind_t { bind_t( Fn fn, Args const& args ) : fn_(fn), args_(args) {} void operator()() { args_.call(fn_); } private : Fn fn_; Args args_; }; template <class Fn, class A1> bind_t< Fn, Args1<A1> > bind(Fn fn, A1 a1) { typedef Args1<A1> args; return bind_t<Fn, args>(args(a1)); } template <class Fn, class A1, class A2> bind_t< Fn, Args2<A1, A2> > bind(Fn fn, A1 a1, A2 a2) { typedef Args2<A1, A2> args; return bind_t<Fn, args>(args(a1, a2)); } struct Test { static void Func(int) {}; static void Func(int, const char*) {}; }; int main(int argc, char **argv) { boost::bind(&Test::Func, 5)(); boost::bind(&Test::Func, 5, "WORKS!")(); bind(&Test::Func, 5)(); bind(&Test::Func, 5, "NOT WORKS!")(); return 0; }

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[btree] Large file support
by Beman Dawes 01 Oct '10

01 Oct '10

The btree library uses low level I/O. On POSIX-like systems that means read/write/lseek. lseek() won't support large files on systems where long is 32 bits. POSIX-like operating systems get around this problem by supply functions with names like llseek or lseek64 that traffic in long long instead of long. So there is a line of code: new_offset = ::lseek(handle(), offset, whence); // offset is a variable of type int64_t That needs to change to something like: #if defined(SOMEOS) new_offset = ::|lseek(handle(), offset, whence); #elif defined(ANOTHEROS) new_offset = ::whatever(handle(), offset, whence); #else new_offset = ::lseek(handle(), offset, whence); #endif Up at the front of the source file there may also have to be special headers included or symbols defined, depending on the operating system. I'd appreciate some help from folks familiar with particular non-Windows operating systems. What is the preferred name for the 64-bit seek function and what is the preferred #if defined(symbol)? Do special headers have to be included or special symbols defined? Thanks, --Beman

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[1.43.0] [variant] Compilation errors when swapping variant type objects
by Adam Badura 01 Oct '10

01 Oct '10

We are using Boost 1.43.0 (we tried to move to 1.44.0 but there were some problems which I reported some time ago) in Visual Studio 2010. And there are some compilation problems when variant type objects are swapped. This does not affect all variant types but I didn't figured out what are the exact conditions (however I guess it is likely something with namespaces and templates). Following code demonstrates the issue: ---------------------------------------- #include <cstdlib> #include <list> #include <boost/variant.hpp> int main() { typedef boost::variant< std::list< int >::iterator > variant_type; variant_type v; variant_type().swap( v ); return EXIT_SUCCESS; } ---------------------------------------- compilation fails with following message: ---------------------------------------- 1>d:\libraries\boost_1_43_0\boost\variant\detail\move.hpp(155): error C2668: 'boost::detail::variant::detail::move_swap::swap' : ambiguous call to overloaded function 1> d:\libraries\boost_1_43_0\boost\variant\detail\move.hpp(141): could be 'void boost::detail::variant::detail::move_swap::swap<T>(T &,T &)' 1> with 1> [ 1> T=T0 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(100): or 'void std::swap<T>(_Ty &,_Ty &)' [found using argument-dependent lookup] 1> with 1> [ 1> T=T0, 1> _Ty=T0 1> ] 1> while trying to match the argument list '(T0, T0)' 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(698) : see reference to function template instantiation 'void boost::detail::variant::move_swap<T>(T &,T &)' being compiled 1> with 1> [ 1> T=T0 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(825) : see reference to function template instantiation 'void boost::detail::variant::swap_with<Variant>::operator ()<T>(T &) const' being compiled 1> with 1> [ 1> Variant=boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>, 1> T=T0 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\detail\visitation_impl.hpp(141) : see reference to function template instantiation 'void boost::detail::variant::invoke_visitor<Visitor>::internal_visit<T>(T &,int)' being compiled 1> with 1> [ 1> Visitor=boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>>, 1> T=T0 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\detail\visitation_impl.hpp(169) : see reference to function template instantiation 'void boost::detail::variant::visitation_impl_invoke_impl<Visitor,VoidPtrCV,T>(int,Visitor &,VoidPtrCV,T *,boost::mpl::false_)' being compiled 1> with 1> [ 1> Visitor=boost::detail::variant::invoke_visitor<boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>>>, 1> VoidPtrCV=void *, 1> T=T0 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\detail\visitation_impl.hpp(252) : see reference to function template instantiation 'void boost::detail::variant::visitation_impl_invoke<Visitor,VoidPtrCV,T0,NoBackupFlag>(int,Visitor &,VoidPtrCV,T *,NoBackupFlag,int)' being compiled 1> with 1> [ 1> Visitor=boost::detail::variant::invoke_visitor<boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>>>, 1> VoidPtrCV=void *, 1> NoBackupFlag=boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>::has_fallback_type_, 1> T=T0 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(1769) : see reference to function template instantiation 'void boost::detail::variant::visitation_impl<first_which,first_step,Visitor,VoidPtrCV,boost::variant<T0_>::has_fallback_type_>(const int,const int,Visitor &,VoidPtrCV,boost::mpl::false_,NoBackupFlag,Which *,step0 *)' being compiled 1> with 1> [ 1> Visitor=boost::detail::variant::invoke_visitor<boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>>>, 1> VoidPtrCV=void *, 1> T0_=std::_List_iterator<std::_List_val<int,std::allocator<int>>>, 1> NoBackupFlag=boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>::has_fallback_type_, 1> Which=first_which, 1> step0=first_step 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(1780) : see reference to function template instantiation 'void boost::variant<T0_>::internal_apply_visitor_impl<Visitor,void*>(int,int,Visitor &,VoidPtrCV)' being compiled 1> with 1> [ 1> T0_=std::_List_iterator<std::_List_val<int,std::allocator<int>>>, 1> Visitor=boost::detail::variant::invoke_visitor<boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>>>, 1> VoidPtrCV=void * 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(1803) : see reference to function template instantiation 'void boost::variant<T0_>::internal_apply_visitor<boost::detail::variant::invoke_visitor<Visitor>>(boost::detail::variant::invoke_visitor<Visitor> &)' being compiled 1> with 1> [ 1> T0_=std::_List_iterator<std::_List_val<int,std::allocator<int>>>, 1> Visitor=boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>> 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(1637) : see reference to function template instantiation 'void boost::variant<T0_>::apply_visitor<boost::detail::variant::swap_with<Variant>>(Visitor &)' being compiled 1> with 1> [ 1> T0_=std::_List_iterator<std::_List_val<int,std::allocator<int>>>, 1> Variant=boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>, 1> Visitor=boost::detail::variant::swap_with<boost::variant<std::_List_iterator<std::_List_val<int,std::allocator<int>>>>> 1> ] 1> d:\libraries\boost_1_43_0\boost\variant\variant.hpp(1631) : while compiling class template member function 'void boost::variant<T0_>::swap(boost::variant<T0_> &)' 1> with 1> [ 1> T0_=std::_List_iterator<std::_List_val<int,std::allocator<int>>> 1> ] 1> d:\test\simple\simple.cpp(10) : see reference to class template instantiation 'boost::variant<T0_>' being compiled 1> with 1> [ 1> T0_=std::_List_iterator<std::_List_val<int,std::allocator<int>>> 1> ] ---------------------------------------- Adam Badura

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