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

thread::id holding resources after thread has exited
by Oliver Seiler 11 Jun '11

11 Jun '11

Hi all -- Long time boost user with some unexpected behaviour related to the use of thread::id; as this isn't in any way obvious from the documentation, I thought it might be of some interest here. In the case where this came up, we had a deadlock which was traced to a thread::id member variable being reassigned. The basic flow goes something like this: * we have a shared resource protected with a mutex that happens to store a thread::id * thread 1 is started using a bind call with a shared_ptr to some resource A; destruction of A will call our shared resource, which in turn requires locking the mutex * the thread::id of thread 1 is stored in the shared resource * thread 1 exits; the unexpected bit is that the last reference to A is held by the function object used to start this thread, which is now being kept active by the thread::id we are still storing * another thread, thread 2, has the mutex of our shared resource locked and assigns its thread id to it * the assignment results in the destruction of the thread::id associated with thread 1, which results in the destruction of A, which in turn tries to lock (again) the mutex in our shared resource, resulting in a deadlock. Initially when I saw the fix for this deadlock I thought that the thread::id was preventing the thread itself from exiting properly, but the deadlock was clear in the thread backtraces we had. This is a somewhat surprising result, and isn't at all apparent from the boost.thread documentation; it makes more sense looking through the code, though. This appears to have the same behaviour across all versions I've looked at (1.36, 1.42, 1.46.1). I wonder if this is a bug; I suspect it would be possible to reset the function object holding the thread entry point when the thread exits, ensuring that any resources held by it are released; it certainly isn't obvious to me that this would be prevented by holding a stray thread::id somewhere. If this is a confusing description, I'm sure I could bang together some code that demonstrates the issue; not typing this at a development box right now. Cheers Oliver

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[Test] can tests be run in parallel?
by Thorsten Ottosen 11 Jun '11

11 Jun '11

Hi all, I was trying to make better use of my cores for running tests. I tried to find something about running tests in parallel in the online documentation, but without any luck. Does anyone know if this is possible? Thanks Thorsten

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Objective-C++ boost integration
by kelvSYC 10 Jun '11

10 Jun '11

I'm wondering if there is any effort either at boost or elsewhere to have a library that integrates the C++ libraries with those of Objective-C++ (or Cocoa, since it seems that most treat the two as synonymous) in a nice way - for example, a smart pointer for Objective-C classes (via something like boost::intrusive_ptr), STL iterators for Objective-C containers, C++ function object integration with Objective-C selectors, etc.

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Re: [Boost-users] Create A Boost Thread for each HW Thread?
by Brad 10 Jun '11

10 Jun '11

Thanks Christoph and Scott! thread_group is exactly what I need. I appreciate the advice. Brad

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boost exception question when threading library header is included.
by Robert Ramey 10 Jun '11

10 Jun '11

I am building a small ap to test the ASIO library. I run my test ap and things run as expected. But when I set my IDE options (MSVC 8.0) to trap when an exception is thrown, I get an exception thrown before main(.. is invoked. The call stack looks like: msvcr90d.dll!_CxxThrowException(void * pExceptionObject=0x0012fc3c, const _s__ThrowInfo * pThrowInfo=0x0047f944) Line 161 C++ time_pair.exe!boost::copy_exception<boost::exception_detail::bad_alloc_>(const boost::exception_detail::bad_alloc_ & e={...}) Line 47 C++ time_pair.exe!boost::exception_detail::get_bad_alloc<42>() Line 80 + 0x9f bytes C++ time_pair.exe!`dynamic initializer for 'boost::exception_detail::exception_ptr_bad_alloc<42>::e''() Line 94 + 0x28 bytes C++ msvcr90d.dll!_initterm(void (void)* * pfbegin=0x004743c4, void (void)* * pfend=0x00474758) Line 903 C time_pair.exe!__tmainCRTStartup() Line 497 + 0xf bytes C time_pair.exe!mainCRTStartup() Line 399 C this seems to point an attempt to copy something non_copyable in the boost.exception library. Can anyone help me understand what's going on here and what I should do about it? Here is a small test which you can use to demonstrate the problem #include <boost/thread.hpp> int main(int argc, char * argv[]){ return 0; } Robert Ramey

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Potential access violation in Boost.Regex
by Сергей Филиппов 10 Jun '11

10 Jun '11

Hi all, recently, I've found a bug in regex that can lead to access violation. std::string s(".*?"); boost::regex regEx(s.begin(), s.end()); // Potential AV here basic_regex constructor creates a local variable of type traits::string_type and passes its the first element address and one-beyond-the-last element address to the assing() function. template <class InputIterator> basic_regex(InputIterator arg_first, InputIterator arg_last, flag_type f = regex_constants::normal) { typedef typename traits::string_type seq_type; seq_type a(arg_first, arg_last); if(a.size()) assign(&*a.begin(), &*a.begin() + a.size(), f); else assign(static_cast<const charT*>(0), static_cast<const charT*>(0), f); } Calling assign() eventually leads to creation of basic_regex_parser object and calling its parse_repeat() function. m_begin and m_end members are initialized with values passed to assign(). template <class charT, class traits> bool basic_regex_parser<charT, traits>::parse_repeat(std::size_t low, std::size_t high) { ... // OK we have a perl or emacs regex, check for a '?': if(this->m_traits.syntax_type(*m_position) == regex_constants::syntax_question) { greedy = false; ++m_position; } // for perl regexes only check for pocessive ++ repeats. if((0 == (this->flags() & regbase::main_option_type)) && (this->m_traits.syntax_type(*m_position) == regex_constants::syntax_plus)) { pocessive = true; ++m_position; } ... } In parse_repeat() the m_position, member points to '?' so condition in the first if is true and m_position is advanced by ++m_position. Now it is equal to m_end. In the next if statement, *m_position is evaluated that may cause access violation. Actually, it is unlikely that the sample code above will cause AV. It is because seq_type in basic_regex constructor is basic_string, and basic_string's underlying buffer is usually null-terminated. So m_end points to the null terminator. It always readable, no AV can happen. The actual code I used is slightly different but the concept is the same: boost::u32regex regEx = boost::make_u32regex(L".*?"); u32regex and make_u32regex are provided by the ICU library. That is a way to support unicode strings. seq_type become std::vector<int,std::allocator<int> >. Some time the "a" object's underlying buffer was allocated right in the end of page, so basic_regex_parser::m_end pointed to the start of the next page that was not allocated. Dereferencing m_position caused access violation. My environment is Visual VC++ 9.0, Boost 1.42.0 (as far I can see, the code in Boost 1.46.1 is the same). By the way. When traits::string_type is basic_string, the code in basic_regex::basic_regex is not portable: assign(&*a.begin(), &*a.begin() + a.size(), f); If I remember correctly, standard does not guarantee that basic_string's controlling sequence is contiguous. Just in case, the call stack when AV occured: boost::re_detail::basic_regex_parser<int,boost::icu_regex_traits>::parse_repeat+0x87 boost::re_detail::basic_regex_parser<int,boost::icu_regex_traits>::parse_extended+0x182 boost::re_detail::basic_regex_parser<int,boost::icu_regex_traits>::parse+0x133 boost::re_detail::basic_regex_implementation<int,boost::icu_regex_traits>::assign+0x98 boost::basic_regex<int,boost::icu_regex_traits>::do_assign+0x14c boost::basic_regex<int,boost::icu_regex_traits>::assign+0x16 boost::basic_regex<int,boost::icu_regex_traits>::assign<int *>+0xa2 boost::basic_regex<int,boost::icu_regex_traits>::basic_regex<int,boost::icu_regex_traits><boost::u16_to_u32_iterator<wchar_t const *,int> >+0xb8 boost::re_detail::do_make_u32regex<wchar_t const *>+0x25 boost::make_u32regex+0x2c Sergey

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(no subject)
by Сергей Филиппов 10 Jun '11

10 Jun '11

Hi all, recently, I've found a bug in regex that can lead to access violation. std::string s(".*?"); boost::regex regEx(s.begin(), s.end()); // Potential AV here basic_regex constructor creates a local variable of type traits::string_type and passes its the first element address and one-beyond-the-last element address to the assing() function. template <class InputIterator> basic_regex(InputIterator arg_first, InputIterator arg_last, flag_type f = regex_constants::normal) { typedef typename traits::string_type seq_type; seq_type a(arg_first, arg_last); if(a.size()) assign(&*a.begin(), &*a.begin() + a.size(), f); else assign(static_cast<const charT*>(0), static_cast<const charT*>(0), f); } Calling assign() eventually leads to creation of basic_regex_parser object and calling its parse_repeat() function. m_begin and m_end members are initialized with values passed to assign(). template <class charT, class traits> bool basic_regex_parser<charT, traits>::parse_repeat(std::size_t low, std::size_t high) { ... // OK we have a perl or emacs regex, check for a '?': if(this->m_traits.syntax_type(*m_position) == regex_constants::syntax_question) { greedy = false; ++m_position; } // for perl regexes only check for pocessive ++ repeats. if((0 == (this->flags() & regbase::main_option_type)) && (this->m_traits.syntax_type(*m_position) == regex_constants::syntax_plus)) { pocessive = true; ++m_position; } ... } In parse_repeat() the m_position, member points to '?' so condition in the first if is true and m_position is advanced by ++m_position. Now it is equal to m_end. In the next if statement, *m_position is evaluated that may cause access violation. Actually, it is unlikely that the sample code above will cause AV. It is because seq_type in basic_regex constructor is basic_string, and basic_string's underlying buffer is usually null-terminated. So m_end points to the null terminator. It always readable, no AV can happen. The actual code I used is slightly different but the concept is the same: boost::u32regex regEx = boost::make_u32regex(L".*?"); u32regex and make_u32regex are provided by the ICU library. That is a way to support unicode strings. seq_type become std::vector<int,std::allocator<int> >. Some time the "a" object's underlying buffer was allocated right in the end of page, so basic_regex_parser::m_end pointed to the start of the next page that was not allocated. Dereferencing m_position caused access violation. My environment is Visual VC++ 9.0, Boost 1.42.0 (as far I can see, the code in Boost 1.46.1 is the same). By the way. When traits::string_type is basic_string, the code in basic_regex::basic_regex is not portable: assign(&*a.begin(), &*a.begin() + a.size(), f); If I remember correctly, standard does not guarantee that basic_string's controlling sequence is contiguous. Just in case, the call stack when AV occured: boost::re_detail::basic_regex_parser<int,boost::icu_regex_traits>::parse_repeat+0x87 boost::re_detail::basic_regex_parser<int,boost::icu_regex_traits>::parse_extended+0x182 boost::re_detail::basic_regex_parser<int,boost::icu_regex_traits>::parse+0x133 boost::re_detail::basic_regex_implementation<int,boost::icu_regex_traits>::assign+0x98 boost::basic_regex<int,boost::icu_regex_traits>::do_assign+0x14c boost::basic_regex<int,boost::icu_regex_traits>::assign+0x16 boost::basic_regex<int,boost::icu_regex_traits>::assign<int *>+0xa2 boost::basic_regex<int,boost::icu_regex_traits>::basic_regex<int,boost::icu_regex_traits><boost::u16_to_u32_iterator<wchar_t const *,int> >+0xb8 boost::re_detail::do_make_u32regex<wchar_t const *>+0x25 boost::make_u32regex+0x2c Sergey

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Create A Boost Thread for each HW Thread?
by Brad 10 Jun '11

10 Jun '11

What's the proper way to start a boost thread for each hardware thread available? I can do this... but it is clunky and does not scale (especially when there are lots of cores): const unsigned int hwt() { const unsigned int t = boost::thread::hardware_concurrency(); return t; } if ( t == 2 ) { boost::thread _01( task, thread_data, St ); boost::thread _02( task, thread_data, St ); _01.join(); _02.join(); } if ( t == 4 ) { boost::thread _01( task, thread_data, St ); boost::thread _02( task, thread_data, St ); boost::thread _03( task, thread_data, St ); boost::thread _04( task, thread_data, St ); _01.join(); _02.join(); _03.join(); _04.join(); } It seems that a for loop (or something similar) could be used to start the same number of boost threads as there are HWTs. Could someone point me in the right direction? Thanks, Brad

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Re: [Boost-users] boost MSDN
by Tom Tan 10 Jun '11

10 Jun '11

you might want to check boost.filesystem at here: http://www.boost.org/doc/libs/1_46_1/libs/filesystem/v3/doc/tutorial.html , more specifically this part : "Directory iteration plus catching exceptions - (tut3.cpp)" boost.filesystem needs building. you could go here to get a pre-built package: http://www.boostpro.com/download/ Hope this helps. > ------------------------------ > > Message: 7 > Date: Fri, 10 Jun 2011 11:39:17 +0800 > From: Peter <lq.yan(a)siat.ac.cn> > To: boost-users(a)lists.boost.org > Subject: [Boost-users] boost MSDN > Dear all, > > I'm a newer to boost library. when i try to use the boost library to get > the files of current directory, I found it is so difficult to get some > help from boost HTML document. > Is there any document could teach me to use boost library API? Most of > time, i use visual studio, MSDN teach me how to use API. > So i think Boost maybe has similar documents to help me improving coding > speed. > -- > > *Regards, > > ??? /Peter,YAN/ > > * > > ?????????? > ????????????????? > Email: lq.yan(a)siat.ac.cn > TEL: +86 755 8639 2301 > >

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(no subject)
by Marco Piacentini 10 Jun '11

10 Jun '11

Marco Piacentini wrote: > Hy...I try to explain better my question... > Im using boost serialization text archive before sending data over > TCP connection... > Now I need to pass the received data to a Java application...so I > would know if the serialized stream is composed only by the data or > by the data + boost serialization(tag, code, etc.)... > In this case my only chance to transfer the data to the java > application, is to filter them before transfering?thanks... Robert Ramey wrote: >I'll try to answer the question - but I'm sort of speculating as to what >you want to do. I throw in some miscellanous observations which >may or may not be helpful. >a) Generally I don't suggest that one tries to use boost serialization >to export data to non C++ applications. The library is intended to >provide the easiest to use and most efficient implementation of >serialization for C++ environments. Any ability to use this to >export data to/from other environments is a coincidence. >b) There are other tools for accomplishing the above. There >is google protocol buffers and there is boost spirit/karma/qi >which handle data in a way that is not connected to C++. Of >course they won't be as automatic as serialization for just this >reason. >large part it consists of not using those parts of the library which >are strongly dependent C++ such as serialization of pointers. A >useful place to start is one of the examples included with the package >which creates a write only archive which can export any data which >includes serialization functions. The leverages the serialization functions >to save a lot of work at the expense of being to read the archive back. >Something like might work for you. >d) there are other examples around for serializing files with JSON >and YAML formats. Again, these would likely mean not using >some of the features of the serialization library - which might be >be fine for you app. >I realize this might not be much comfort - but hope it helps >anyway. Thanks...unfortunately the analisys and design phases was very poor in the project in which I work....I'll try to follow your advices...bye!

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