July 2009 - Boost-users - lists.preview.boost.org

asio: transporting exceptions across threads
by Zachary Turner 21 Jul '09

21 Jul '09

Suppose I have some io_service object in which I call run() from thread A. Thread A is the main controller of the i/o operations and does things like issuing reads and, upon completion, issuing writes for those reads. The writing service might wish to spawn off some child services that runs in thread B. So when thread A says writer.async_write_data() all it really does is call child_writer_service.post() with the data. Supposing an exception occurs in thread B, what is the best way to have this terminate the entire asio pipeline and propagate the exception all the way up to outside of thread A's call to io_service::run()? I've looked at the sample code on the boost::exception tutorial but I'm unable to apply this to the situation in asio, either due to differences in the threading model or due to my own misunderstandings. Thanks

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where is the pdf documentation?
by Ozgur Ozturk 21 Jul '09

21 Jul '09

Hi, I see mention of pdf documentation, but couldn't find it online. Can someone give the link to it? Thanks, Best regards, Ozgur (Oscar) Ozturk www.DrOzturk.com Phone: +1 (908) DROZGUR i.e, +1 (908) 376-9487

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usage of boost::asio::async_write and boost::asio::buffer
by Ozgur Ozturk 21 Jul '09

21 Jul '09

Hi, I am modifying example echo server for my server. I started to get the attached error, and I suspect I am using buffer incorrectly since error started after a change there. I just changed a line from boost::asio::async_write(socket_, boost::asio::buffer("1^", 3, boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); to boost::asio::async_write(socket_, boost::asio::buffer(replyString, replyString.size()), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); I generate the replyString to have results from my database query separated with ^ signs (which is used to tokenize the replyString on the client side...) string replyString="1^"; while(res->next()) { replyString+=res->getString("nickname")+"^"; } I checked that replyString.size() is really one more than the final filled position index in replyString. Any ideas, suggestions? TIA, Best regards, Ozgur (Oscar) Ozturk www.DrOzturk.com Phone: +1 (908) DROZGUR i.e, +1 (908) 376-9487

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Docs missing info about which headers to include?
by Jason Cipriani 21 Jul '09

21 Jul '09

I'm new to much of boost. It is less than ideal to have to search through boost headers to find which ones to include for a class (e.g. boost::scoped_lock). Where can I find information about which headers the classes are in? It does not seem to be in the documentation, e.g.: http://www.boost.org/doc/libs/1_37_0/doc/html/boost/interprocess/scoped_loc… This is strange to me, since this type of info is pretty fundamental. In that particular case, after trying boost/thread/scoped_lock.hpp and boost/interprocess/scoped_lock.hpp, I resorted to searching through files and eventually found it in boost/interprocess/sync/scoped_lock.hpp (among other locations, but that one seems to be the most reasonable). Is there some place in the boost docs where I can find what headers to include to use the classes? Thanks, Jason

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Re: [Boost-users] Spirit 1.39 compilation times (avi)
by Avi Bahra 21 Jul '09

21 Jul '09

Can someone explain why the compilation times are faster under Spirit2.1 I have noticed that even boost 1.39 references spirit qi, can I assume that faster compile times are due to moving from spirit classic to spirit qi ? More importantly can we intermix classic and qi grammars, if not are there any migration notes, to help users -- Best regards, Ta, Avi

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Off Topic: Boost Book
by Etienne Philip Pretorius 21 Jul '09

21 Jul '09

Hello List, Any thoughts about this book: http://www.amazon.com/Beyond-Standard-Library-Introduction-Boost/dp/0321133… Also, any other recommendations (for boost) will be appreciated. Thank you, Etienne

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[log] More than one module but static linking?
by Boris Schaeling 21 Jul '09

21 Jul '09

Andrey, the documentation of your very useful logging library says: "If your application consists of more than one module (e.g. an exe and one or several dll's) the library must be built as a shared object." As it turns out I want to use your library in such an application. However there is only one module writing to the log file. Do I still need to use the shared library? Or can I link statically if for example I don't use certain parts of the library? As far as I see there is no more information in the documentation why linking dynamically is forbidden? Boris

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boost::mpl::inherit from a typelist?
by Zachary Turner 21 Jul '09

21 Jul '09

When I use typedef boost::mpl::inherit<boost::mpl::list<udt1, udt2, udt3> >::type derived_class; (at least in MSVC) then it inherits directly from boost::mpl::list, instead of inheriting from the individual members of the list. Is there a way to make it inherit from each type in the list instead? inherit_linearly appears to accept anything modelling the ForwardSequence concept as its template argument, so it seems like inherit should do the same unless I'm just missing something.

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[lambda] instantiation in bind
by Igor R 21 Jul '09

21 Jul '09

In VC9.0 the following code gives the error message: 1>...\boost\tuple\detail\tuple_basic.hpp(419) : error C2259: 'Base' : cannot instantiate abstract class If the Base is not abstract, the code compiles and works as expected. Unfortunately, I'm unable to realise why it tries to instantiate the Base, and how to overcome this issue, so any enlightenment would be greatly appreciated! class Base { public: virtual void close() = 0; }; class Derived : public Base { public: void close() {} }; #include <boost/shared_ptr.hpp> typedef boost::shared_ptr<Base> BasePtr; typedef boost::shared_ptr<BasePtr> BasePtrPtr; #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> namespace bl = boost::lambda; BasePtrPtr makeHolder(Base *base) { return BasePtrPtr(new BasePtr(base), bl::bind(&Base::close, **bl::_1)); } int main() { Base *b = new Derived(); makeHolder(b); return 0; }

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[boost][format] How does one determine the number of format arguments?
by Neil Groves 21 Jul '09

21 Jul '09

Dear all, Please accept my apologies if this ends up being a double post. I am having trouble with posting to the boost mailing lists. I have the need to obtain the number of 'arguments' (the %1% thingies!) in a boost::format. Is this functionality supported in a manner that I have failed to find in the documentation? If it is not supported, would it be a worthwhile addition since it seems easy to add assuming the num_args_ member variable is the information I require and that validation code of boost::format instances is commonly very useful. I have rarely executed error code that uses boost::format that is difficult to test, but by adding a StringTable that loads at module startup and wraps the boost format, I can provide compile-time validation of much of the formatting code, and runtime validation of the format strings at module startup. This would make it much easier to test. Thank you for your time and consideration. Regards, Neil Groves

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