July 2003 - Boost-users - lists.preview.boost.org

Known limitations of Boost threads across O/S platforms???
by Louis Caston 17 Jul '03

17 Jul '03

Are there any known limitations to Boost threads across Win, Solaris, and Linux? I'm in a planning cycle, and expect to be utilizing Boost as much as possible. Thanks, - Louis

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indirect_iterator_generator<list<shared_ptr<X> >::iterator> again
by Raoul Gough 17 Jul '03

17 Jul '03

Using gcc 3.2 (on MinGW) the template parameter defaults for indirect_iterator_generator don't work with shared_ptr. This has been discussed* on the list before, but there doesn't seem to have been a user-friendly resolution to the issues involved (at least not in release 1_30_0). Using my compiler, the current situation requires the client code to supply all five of the template parameters. *some previous threads on the subject: http://groups.yahoo.com/group/Boost-Users/message/1618 http://lists.boost.org/MailArchives/boost/msg33273.php http://lists.boost.org/MailArchives/boost/msg33316.php My sample code: #include <boost/iterator_adaptors.hpp> #include <boost/shared_ptr.hpp> #include <list> int main () { typedef std::list<boost::shared_ptr<int> > ListType; typedef ListType::iterator BaseIterator; typedef boost::indirect_iterator_generator<BaseIterator>::type Adapter; } Error output: f:/mingw/include/c++/3.2/bits/stl_iterator_base_types.h: In instantiation of `std::iterator_traits<boost::shared_ptr<int> >': d:/CVS/boost/boost/boost/iterator_adaptors.hpp:1111: instantiated from `boost::detail::iterator_traits<boost::shared_ptr<int> >' d:/CVS/boost/boost/boost/iterator_adaptors.hpp:1111: instantiated from `boost::detail::traits_of_value_type<main()::BaseIterator>' iterator_adapter.cc:9: instantiated from here f:/mingw/include/c++/3.2/bits/stl_iterator_base_types.h:123: no type named ` iterator_category' in `class boost::shared_ptr<int>' f:/mingw/include/c++/3.2/bits/stl_iterator_base_types.h:125: no type named ` difference_type' in `class boost::shared_ptr<int>' Looking at iterator_adaptors.hpp:1111 we have (reformatted): struct traits_of_value_type { typedef typename boost::detail::iterator_traits<T>::value_type outer_value; typedef typename boost::detail::iterator_traits<outer_value>::value_type value_type; typedef typename boost::detail::iterator_traits<outer_value>::reference reference; typedef typename boost::detail::iterator_traits<outer_value>::pointer pointer; }; So traits_of_value_type tries to look up the *iterator_traits* of the *value type* for the supplied iterator. Does the value type really need to have complete iterator traits for the compiler to figure out the defaults here? Is anybody working on improving the ease-of-use for indirect_iterator_generator? -- Raoul Gough "Let there be one measure for wine throughout our kingdom, and one measure for ale, and one measure for corn" - Magna Carta

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Preventing Cycles with shared_ptr
by Jason Winnebeck 17 Jul '03

17 Jul '03

Hello everyone, I am new to this list and a little new to Boost. I have a question on program design when using the excellent boost shared pointer's library. I am converting my old network library that uses explicit memory management to use shared_ptr where appropriate. So far this has gone well but I am having problem with cycles. This post is more of request for comments on my thought process, and if there is a "traditional" or better way of handling these issues. The question in general is "How to deal with the cycles that come about from event generator/listener designs?" The problem in more specific terms with my thinking follows. I'm having a problem with trying to mitigate reference cycles in a event generator/event listener paradigm. One creates a listener object, and registers itself as a listener of that object. As a result of the event, it may want to invoke methods of that object, so it contains a reference to that object. So Generator contains a reference to Listener, and Listener contains a reference to Generator. This is a problem with reference counted pointers. People tell me that cycles in general signify a flaw, so perhaps my fundamental design is indeed flawed. A real example from my library is a Connection object representing a network connection. Library user derives a new class implementing the ConnectionListener interface and registers it with Connection. When a packet arrives an event in the listener is invoked, and let's say the listener wants to process the packet and send a packet in response. It does this by passing a packet to the Connection. Thus the Connection refers to the listener, and the listener refers to the Connection (to send a packet). There are some possible solutions. One way to break cycles is to use weak references. In this way you can observe an object without preventing it from being collected. In the general case, cycles are very bad because you aren't sure which object can be deleted when. However in this case the relationship is simple. Generator can only generate events when it is alive, and Listener will only try to interact with Generator as a response to its event (so we know Generator is alive if we got its event). One could use a weak pointer in the Generator to the Listener, but then the Listener may die as soon as it is registered. The Listener can use a weak pointer to the Generator, and this seems intuitive since the Listener is merely an observer, but accessing a weak pointer safely in a multithreaded environment is expensive (I think so?) when we are positive it exists. The issue is compounded in my library since Generator is an object that I have written (therefore I can trust it to understand all of my "choices"), while the Listener is defined by the user. So I prefer to make the task as easy as possible on the user -- so I want to allow the user to use weak or strong references if possible so he doesn't have to worry about cycles. If I must impose a restriction along the lines of "you can have a pointer to object type x", I will, but I much prefer to not have restrictions like that. One way I've been considering (and have implemented some already) is to have the Generator release all its Listeners when it is done generating events. This works, but in my old API I have ways to retrieve the set listener, and this cannot work since the set listener may go to NULL at any time (as a weak pointer). So my best option for now seems to be to break my old API by allowing the user to set listeners and objects but not be able to retrieve them back (or allow retrieve function knowing that an empty shared_ptr may be returned). Another possible way is for the Generator always to pass a reference to itself in the event. This is possible and clean and very fast, but requires major changes to my API, but the prior way of disallowing gets is safe in that it allows the user to not have to think twice about keeping a reference to my object. I have more ideas but this post is getting long. If you have comments about how something like this using shared_ptr is typically designed, or comments related to my more specific problem, I would be grateful. Thanks in advance, Jason Winnebeck

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RE: [Boost-Users] Preventing Cycles with shared_ptr
by Jim.Hyslop 17 Jul '03

17 Jul '03

Jason Winnebeck wrote: > I am converting my old network library that uses explicit memory > management to use shared_ptr where appropriate. So far this has gone > well but I am having problem with cycles. [...] > One could use a weak pointer in the Generator to the > Listener, but then > the Listener may die as soon as it is registered. That's OK, though - each time the Generator wants to use the Listener, it constructs a shared_ptr out of the weak_ptr it has. If the shared_ptr is NULL, the Generator knows the Listener has gone away, and can take the appropriate steps to unregister the Listener. > ... the Listener is defined by the user. So I prefer to > make the task as easy as possible on the user -- so I want to > allow the > user to use weak or strong references if possible so he > doesn't have to > worry about cycles. If you want to make things easy for the user, don't offer them a choice. Choice means complexity. Complexity is bad. Require the user to use a shared_ptr to the Generator. -- Jim

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RE: [Boost-Users] vc6 stl's problem
by Jim.Hyslop 17 Jul '03

17 Jul '03

hlh771 wrot: > the stl's implementation of vc6 is buggy such as auto_ptr,xtree etc, > even if it is patched with sp5 The Service Packs do not include changes to the STL headers. The STL was provided by a third party, Dinkumware, which for a few years was unable to provide updates to Microsoft due to legal difficulties between Dinkumware and another party. You can find patches and fixes at Dinkumware's web site: http://www.dinkumware.com/vc_fixes.html -- Jim

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how to empty a graph?
by Jeremie 17 Jul '03

17 Jul '03

Hello guys, I'm a newbie with boost and I need to empty a Mutable graph in the program I'm doing. is ther another method as remove_edge? /Jérémie

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regex RegEx::Grep on Windows [callback problems with bind1st(mem_fun(callback))]
by Eric Brown (Propel) 16 Jul '03

16 Jul '03

I'm trying to use RegEx::Grep(GrepCallback cb, ...) on Windows with VC6. It works great with one exception. I really need the callback to be a method so that I can update attributes in my instance. I've tried about 10 ways and can't get anywhere - VC6 keeps sending back errors. Some of the errors are obvious and some - well, aren't templates wonderful whe it comes to error msgs?!@#$% I'm using MS stl and the example in the docs to get a generic function pointer doesn't work. This is the example in the regex docs: std::bind1st(std::mem_fun(&MyClass::callback), this) Then I tried: boost::bind(&MyClass::callback, this, _1) This simply produces a type that refuses to match GrepCallback. I wish the RegEx code just overloaded RegEx::Grep() to support this. (Is it more crossplatform and the STL way to do things?) I tried several other things including direct casts to GerpCallback, but I'm stuck. Any help in this area would be great. Thanks, Eric

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Standardization of build
by Johannes Strömberg 16 Jul '03

16 Jul '03

Hi, I noticed that the build of some projects (filesystem, date_time, signals) differs from the build of the thread, regex and python libraries in that they they do not include a bin-stage and that debug and release versions have the same name. It would be nice if this could be standardized somehow (especially that debug and release versions should have different names). /Johannes

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Re: [Boost-Users] Re: Is vc7 test unresolved external cpp_main still a problem?
by dick.bridges＠tais.com 16 Jul '03

16 Jul '03

I guess I must have missed those missives. I used <query>boost vc7 test "unresolved external" "cpp_main"</query> to query Google and, as I indicated, only found entrys from last February and none of them contained your nai as the sender. My query was apparently deficient in some manner. Which "FAQ section" mentions it? I tried (and just now reviewed) http://www.boost.org/more/faq.htm but didn't see anything that seemed to cover relevant changes since last February. In any case, my apologies for having not been more diligent. I guess I can assume from the referenced repetitions that the answers to my questions are: 1) no, you didn't miss an update; and 2) yes, it's still expected behavior when using the Jamfile included in the boost_1_30_0.zip currently on SourceForge. Thanks for your time and the clarification. "Gennadiy E. Rozental" To: Boost-Users(a)yahoogroups.com <rogeeff(a)mail.co cc: m> Subject: [Boost-Users] Re: Is vc7 test unresolved external cpp_main still a problem? 07/15/2003 07:33 PM Please respond to Boost-Users > libs\date_time\build\bin\boost_date_time.dll\vc7\debug\runtime- link-dynamic\boost_date_time.dll As I keep repeating DLL version of Boost.Test components is not available for NT platform at the moment. It's already fixed in Jamfile and mentioned in FAQ section. Use static linking instead. Gennadiy. Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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vc6 stl's problem
by hlh771 16 Jul '03

16 Jul '03

the stl's implementation of vc6 is buggy such as auto_ptr,xtree etc, even if it is patched with sp5, my question is: If I use the vc6's stl to build the boost library,is the boost library also buggy?If no, how boost library handle it? If I fix some stl's source files of vc6, will it affect boost?

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