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boost replacement for std::ostringstream
by Chris Stankevitz 07 Sep '12

07 Sep '12

Hello, Does boost provide a replacement for std::ostringstream? If so, can you please tell me the name so I can read the docs on it? The first thing I am going to read is whether or not such a best would provide "reserve". I would like to do this: //----- std::ostringstream Stream; // Stream.reserve(99999); // error: std::ostringstream does not provide reserve Stream.write(pBuffer, 99999); //----- Thank you, Chris

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Boost.Hash and enums
by Filip Konvička 07 Sep '12

07 Sep '12

Hi, In Boost 1.51, it looks to me like boost::hash_value no longer knows how to handle enums anymore. Is the following the right way to tell it to treat enums like ints? #if (BOOST_VERSION >= 105100) // Boost 1.51.0+ namespace boost { /// Enable hashing of enums. template<typename E> size_t hash_value( E const e, typename std::enable_if<std::is_enum<E>::value, E>::type def = static_cast<E>(0)) { return hash_value((int)e); } } #endif Is enum hashing support going to be added to the library in the future? Thanks, Filip

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Re: [Boost-users] Why is there so much co-dependency in Boost? Is there anything to be done about it?
by steve＠parisgroup.net 07 Sep '12

07 Sep '12

Hi again, I'm the original poster that started this thread. WOW! Thanks for all of the great responses. I apologize for posting this message and then getting called away on a business trip. It is only just now that I'm getting back to see what kind of response I got, and I'm thrilled. I'm happy to see that a number of folks involved with Boost see this issue as a significant problem, if only to certain types of companies. APOLOGY: I must apologize for a small mistake in my numbers, that might be somewhat important to someone. I managed to reverse the counts for the "Smart Ptr" and "String Algo" libraries. I remember thinking it kinda strange that one referenced more modules but the other referenced more lines. So it's really true that "String Algo" causes 382 files to be read, while "Smart Ptr" causes only 180 to be read. Sorry about that. I've taken a first pass through all the responses, and rather than respond to each of them individually, I'll offer some more information here and attempt to address address some of the questions that have been pointed back to me. 1) How did I get these numbers. Give some examples. Here's one of the places I'd love to be shown to be wrong. If my numbers are inflated, my sales job to my boss will be that much easier. So by all means, someone correct me if my approach is unsound. What I did was very simple. All I did was compile a very simple program and have g++ give me a list of all of the headers it read during the compilation, excluding system headers. This is done using the following line from my test Makefiles: $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c $< 2> /dev/null -MM > headers.lst Here's the test for SmartPtr: #include <iostream> #include <boost/smart_ptr.hpp> using namespace std; int main(int argc, char* argv[]) { return 0; } This simple test produces a file named headers.lst with 180 unique header paths in it, all starting with "boost/". Discovering the modules used by each module took a few hours of fairly tedious labor, where I sorted and then grouped each list of headers, where each group consisted of headers coming from the same module. 2) Here are the specific module dependencies: Any: "base", Config, Exception, MPL, Preprocessor, Static Assert, Type Traits, Utility Filesystem: "base", Config, Exception, Functional, Integer, Iterators, MPL, Preprocessor, Smart Ptr, Static Assert, Type Traits, Utility SmartPtr "base", Config, Exception, MPL, Preprocessor, Static Assert, Type Traits, Utility StringAlgo: "base", Bind, Compatibility, Concept Check, Config, Exception, Function, Integer, Iterators, MPL, Preprocessor, Range, Static Assert, String Algo, Type Traits, Utility 3) In response to the suggestion to not use the convenience headers, like say "smart_ptr.hpp" as apposed to a header for an individual header type. It's bad enough to tell my programmers they can only use certain Boost modules. To tell them that they can only use certain parts of certain Boost modules just gets to be too much. Plus, I can see eventually using most, if not all of the functionality of the SmartPtr module. The same can be said for the other modules I'm interested in. If I have to run to my boss every time I want to use one new particular feature from a Boost module, it's not worth the effort. Nor would it be worth the overhead of figuring out how to police such a level of code use. So for better or worse, my consideration of the use of Boost has to be on a Module by Module basis. 4) In response to "the license says that it's free to use, and the copyright holders have agreed to that license, so everything is fine". That's not true in the legal world. Neither the license nor any statements made by the person stating a copyright mean anything if that person somehow, if intentionally or unintentionally, included some bit of someone else's code in what they are calling their own. If the original writer of the code can prove original authorship of the code, nothing done without THAT PERSON'S GRANT OF LICENSE means anything. That original author owns all rights to the use of that code, and can dictate how it can and cannot be used. It is this issue that concerns companies like mine. 5) In response to "Who cares how much code there is. How does one "vet" a piece of code, regardless of how much of it there is". It is not hard to look at 100 or 1000 lines of code in a few files and say "there's nothing novel here". If the code is all written to do one basic thing or set of things in a direct way, it's pretty easy to believe that a single or a few individuals wrote the code. And, if the claimed authorship is invalid, real damages would easy to justify as being minimal, given the very limited scope of what the code is capable of doing. It's also much easier to feel comfortable in the fact that many other developers are using these 1000 lines of code in their commercial products and haven't yet been sued over the use of some portion of it. And if/when one wants to upgrade to the next version of a module consisting of 1000 lines of code, it's pretty easy to see what was added/removed. But in the case of boost, with hundreds and possibly thousands (with fuller adoption) of individual files involved, consisting of tens to hundreds of thousands of lines of code, you can't have any idea what you've got In fact, you can feel fairly confident that all of those lines of code are NOT NECESSARY in the basic sense to the benefit you wish to gain from the module in question. So you have to ask yourself "what more does all this code do?", and you certainly can't read and understand the purpose of every line of such a quantity of code to answer that question And the fact that there's so much of it, leads one to wonder "what novel things might be going on in that code to require so much of it"? I mean, 384 header files being read for a Smart Ptr library is pretty darn "novel" in and of itself. Finally, there's mere statistics involved. If 1000 lines of code opens a company to a certain amount of negative exposure, 100,000 lines of code, one might argue, opens the company to 100 times as much exposure. 6) And...I'm not sure this question was asked specifically, but I'll ask it myself..."what are you so worried about". Here's an example of what we're worried about.... Say we develop a tool for Disney to use on one of its feature length films. A month before the premier date of the film, someone takes Disney to court and claims that one of their production tools, the one we wrote, contains code that was stolen from them. Disney asks us to come to court to defend our use of that code. In the case of 1000 lines, we can say exactly what we did to vet the use of the code, and state exactly what that code does not just for us but for anyone who might use it, pointing out that each of those users has a very clear idea of what the code does, what it's worth to them, and why they considered the copyright given by the supposed author to be valid. For 100,000 lines of code we say, well the 1% of the code we use kinda/sort works by doing this, but it does that by going off and using bits and pieces of all these other files, and frankly, we couldn't take the time to understand what all that code is for, and therefore can not possibly have understood that the code contained something novel that might have been misrepresented as to its authorship for reason of personal gain on the part of the offending copyright grantor. In the first case, maybe the judge puts some value on the 1000 lines of code, and because it's Disney, that number gets multiplied by 10X. It's still a small amount of money for Disney, so they pay the money and just decide never to do business with us again. In the second case, the judge says "wow, there's a lot of code here. This is going to take a lot of time to work out the ramifications of, and to put a dollar amount on" and files an injunction against Disney releasing their film. This costs Disney many millions of dollars on everything they've set in motion in order to release the film, that will now all be wasted money. Disney sues us for all of that money. We, as a very small software company, talk to our lawyer, who tells us our best bet is to fold the company and go find jobs working for Google. 7) Use a more modern C++ Some of our customers are in the Operating System Stone Age. For example, I often develop on Fedora, but my code has to be able to compile and run on Red Hat 5. AND, we are often told exactly what compiler to use, and that compiler sometimes not open source, and in a few cases no longer supported. So solving these issues with newer compilers is not an option. 8) Conclusion So, it DOES MATTER, IN A BIG WAY how much code I have to bring into my project's codebase to get SmartPtr capabilities. And even if it turned out that it didn't, my boss doesn't consider it worth the risk to make that call. He'd rather hire another programmer just to write a SmartPtr library, so that our project can stay on schedule and he can sleep at night, knowing his company isn't going to some day go "poof" due to a relaxed approach to using Open Source. Some of our customers don't allow their engineering departments any access to code on the internet for this very reason. There are firewalls designed solely to look for and disallow anything that looks like significant code or other data from coming into the company walls. We have to justify our use of each specific piece of Open Source to EACH OF THESE COMPANIES before we can begin to supply them with anything. So another big issue for us is that as soon as we say "We use Boost", we are dismissed from consideration for a project. I bet this happens all the time. Thanks All for all the interesting and valuable discourse! Take care! Steve PS) My company DOES already use the Boost Smart Ptr library. However, it uses a much earlier version of the library, one that depends on just a dozen or so headers. So I guess at one point individual Boost modules were more separable. Or maybe it was just generally smaller back when that module was adopted. So we DO already have and use Boost Smart Ptrs...we just don't have all the nifty new features in the latest and greatest, the most important of which is the ability to not require that the pointed to class be defined wherever a Smart Ptr is instantiated. I'm dying for that feature.

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[mpi] Linking with MPICH2 under Cygwin
by Murphy, John T. 07 Sep '12

07 Sep '12

Hello all, I recently posted two messages concerning linking boost.mpi with MPICH2 under Cygwin. For the list archives, the solution to this problem was to make sure that the boost libraries were created using the link=static and runtime-link=static boost build options, which creates libraries appropriate for static linking (and marked with a -s infix). When linked statically to the MPICH libraries and the appropriate boost libraries my code can execute correctly. Best, John -- John T. Murphy Computational Postdoctoral Fellow Decision and Information Sciences and Argonne Leadership Computing Facility Argonne National Laboratory jtmurphy(a)anl.gov

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boost::asio buffer questions, and boost::bind question
by Littlefield, Tyler 07 Sep '12

07 Sep '12

Hello: I had a couple of questions. I'm really confused about how the buffers in boost::asio work. I'm using async_read_until, and it wants a streambuf. so I looked at that, and it's a typedef for basic_streambuf. so I'm looking at how to set one of these up, and stackoverflow shows something like: boost::asio::streambuf streamBuffer; boost::asio::streambuf::mutable_buffers_type mutableBuffer = streamBuffer.prepare(max_length); so I'm curious what the mutable buffer is, and how it wraps around streambuf. I'm also curious how people generally handle buffers in their classes. I have a Session class, which will hold a buffer of data to be read, so that when I call HandleRead, it can just look at that buffer for the last line read in. Do I need to store a mutable_buffer and a streambuf? Or is the streambuf ok (and can I pull the data out of it somehow). Also, in that article it shows that it wraps the mutableBuffer in a boost::asio::buffer(what's the point in that?) Finally, my boost::bind question. I was curious how that worked out. When I use _1, _2 as placeholders, does the templating get substituted in somehow? Does it somehow construct an object that just has a () operator to take arguments? Also, if I wanted to write something to let me pull in the errors like placeholders, how do placeholders work/get translated out? Thanks, -- Take care, Ty http://tds-solutions.net The aspen project: a barebones light-weight mud engine: http://code.google.com/p/aspenmud He that will not reason is a bigot; he that cannot reason is a fool; he that dares not reason is a slave.

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Boost.Thread win32 mutex implementations
by Collin Dauphinee 06 Sep '12

06 Sep '12

I was just looking at the win32 implementations of the various Boost.Thread mutex classes (specifically basic_recursive_mutex). I was surprised to see that they use WaitForSingleObject internally, rather than a CRITICAL_SECTION. I've found mentions that it originally used a CRITICAL_SECTION, but no explanation of why it was changed. It seems to me, personally, that the hybrid locking functionality of the CRITICAL_SECTION implementation would be more desirable than the WaitForSingleObject implementation in most use cases. Is there a reason for this choice? At first glance, it looks like it was just done to re-use code from the timed_mutex, which can't (easily) be implemented with CRITICAL_SECTION. Regards, Collin

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Re: [Boost-users] Accessing MSM attribute under specific conditions causes non-compile
by Chiem Whua Ma 06 Sep '12

06 Sep '12

Thank you for your help! I see now that it's not that that the sub-machine is a state of the main machine, but ANY time you have an entry action performed directly from the machine level the fsm is reported as a state and not as an fsm. This isn't a problem since I know this is happening, but perhaps it might be possible to change this so fsm entry actions put the fsm in the fsm parameter slot? What is fsm equal to when an entry action is performed? Here's some code that shows exactly what can be set where and when for anyone else who is trying to figure this out... #include <vector> #include <iostream> #include <boost/msm/back/state_machine.hpp> #include <boost/msm/front/euml/euml.hpp> using namespace std; using namespace boost::msm::front::euml; namespace msm = boost::msm; namespace MSM_A // Concrete FSM implementation { BOOST_MSM_EUML_DECLARE_ATTRIBUTE(int, borrowedBuffer_attribute); BOOST_MSM_EUML_DECLARE_ATTRIBUTE(int, someother_Attribute); BOOST_MSM_EUML_ACTION(someAction) { template <class Event,class FSM,class STATE> void operator()(Event const& event,FSM& , STATE& state) { std::cout<<"Doing someAction."<<std::endl; state.get_attribute(borrowedBuffer_attribute)=1; } }; BOOST_MSM_EUML_ACTION(someOtherAction) { template <class Event,class FSM ,class STATE> void operator()(Event const& event,FSM& fsm, STATE& state) { std::cout<<"Doing someOtherAction."<<std::endl; fsm.get_attribute(borrowedBuffer_attribute)=1; state.get_attribute(someother_Attribute)=1; } }; BOOST_MSM_EUML_EVENT(someevent) BOOST_MSM_EUML_STATE((someOtherAction, no_action, attributes_<<someother_Attribute), someStateA) BOOST_MSM_EUML_STATE((no_action), someStateB) BOOST_MSM_EUML_TRANSITION_TABLE(( someStateA + someevent == someStateB ),transition_table) BOOST_MSM_EUML_DECLARE_STATE_MACHINE(( transition_table, init_ << someStateA, someAction, // <-------------------- ACTION IS AN ENTRY ACTION no_action, attributes_ << borrowedBuffer_attribute, configure_ << no_configure_ ), MSM_A_frontEnd) //fsm name typedef msm::back::state_machine<MSM_A_frontEnd> MSM_A_player; } namespace MSM_B // Concrete FSM implementation { ::MSM_A::MSM_A_player subMachine; BOOST_MSM_EUML_DECLARE_ATTRIBUTE(int, rootFSM_attribute); BOOST_MSM_EUML_DECLARE_ATTRIBUTE(int, rootstate_attribute); BOOST_MSM_EUML_EVENT(someEvent) BOOST_MSM_EUML_ACTION(rootFSM_action) { template <class Event,class FSM,class STATE> void operator()(Event const& event,FSM& , STATE& state) { std::cout<<"Doing rootFSM_action."<<std::endl; state.get_attribute(rootFSM_attribute)=1; } }; BOOST_MSM_EUML_ACTION(another_rootFSM_action) { template <class Event,class FSM,class STATE> void operator()(Event const& event,FSM& fsm , STATE& state) { std::cout<<"Doing another_rootFSM_action."<<std::endl; fsm.get_attribute(rootFSM_attribute)=1; state.get_attribute(rootstate_attribute)=1; } }; BOOST_MSM_EUML_STATE((another_rootFSM_action, no_action, attributes_<<rootstate_attribute), someState) BOOST_MSM_EUML_TRANSITION_TABLE(( someState + someEvent == someEvent ), transition_table) BOOST_MSM_EUML_DECLARE_STATE_MACHINE(( transition_table, //STT init_ << subMachine << someState, rootFSM_action, // Entry no_action, // Exit attributes_ << rootFSM_attribute, // Attributes configure_ << no_configure_ ), MSM_B_frontEnd) //fsm name typedef msm::back::state_machine<MSM_B_frontEnd> MSM_B_player; } int main() { std::cout<<"Making player."<<std::endl; MSM_B::MSM_B_player player; std::cout<<"Starting player."<<std::endl; player.start(); std::cin.ignore(1); return 0; }

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Why is there so much co-dependency in Boost? Is there anything to be done about it?
by steve＠parisgroup.net 06 Sep '12

06 Sep '12

Greetings, As a veteran C++ programmer, I've been an admirer of the Boost library for many years. I've used it at a number of companies I've worked for, especially the SmartPtr library. Right now I'm working for a company that worries a lot about negative exposure to Open Source software issues such as questions that might arise about authorship, copyright or even patent issues. The company does allow the use of Open Source software, but it requires that each piece of code that is brought in first be justified and vetted. Unfortunately, I'm finding this to be a nearly impossible task when I look at the amount of code that must be compiled to use the Boost modules I'm interested in. I've done a study and written some tools, to determine just how many Boost header files must be included to use some of the Boost modules. The numbers are staggering: Any: 79 FileSystem: 276 Smart Ptr: 382 String Algo: 180 I went on and did a tally of which modules these header files came from. Here are the counts for how many other Boost modules each of these modules depends upon: Any: 8 FileSystem: 13 SmartPtr: 8 String Algo: 15 Given these numbers, I think I have to abandon any thoughts of using Boost within my current company. There's no way I'm going to get approval to bring so much code into our work just to get a SmartPtr or FIleSystem library. This is unfortunate, because due to Boost's existence there doesn't seem to be much work going on out there to offer lighter weight alternatives. I'm writing this request in the hopes that there's something I'm missing here, and that someone can point out my folly. Is there a way to utilize any of these Boost modules in such a way that they do not require the inclusion of so much code? If not, does anyone have any suggestions as to how to make this fly with my boss? Has this issue come up before and been considered by the Boost designers? I find the issue baffling. TIA for any help or insight anyone can provide. Steve

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[mpi] broadcast performance
by Brian Budge 06 Sep '12

06 Sep '12

Hi all - I need some advice for using the broadcast function of boost::mpi. We have a large buffer (sometimes gigabytes) that we need to get to all child nodes. We currently use boost::serialization with a binary archive to write the data into a std::vector<char>. Then we send that data across, and deserialize. The data is sent with MPI_Bcast. I've started testing with similar functionality using boost::mpi::broadcast to handle serialization and deserialization. Tracing through the code, it seems that the data is sent to all the child nodes via isend. Is there something I can do to ensure that Bcast will be used instead? If I only have a couple of nodes, the former is fine, but with more nodes, the MPI implementation of Bcast may do a better job (logarithmic or even constant time with the number of nodes). What are the suggestions for getting fast broadcast in this case? I don't think that using skeletons will help, since each instance of the broadcast will have unique data with potentially different layouts. Thanks, Brian

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serialisation use of asserts versus throw ?
by Avi Bahra 06 Sep '12

06 Sep '12

This is question about use of asserts in boost serialisation. As a program migrates from one release to another the api changes. This is expected. In my case I have client/server that uses boost serialisation. I was expecting an throw due to the incompatibility not a an assert. The assert crashes my client, giving no chance for recovery, and informing the user that they are using previous out of date release/server. In may case: boost_iarchive.cpp inline const basic_pointer_iserializer * 399 basic_iarchive_impl::load_pointer( 400 basic_iarchive &ar, 401 void * & t, 402 const basic_pointer_iserializer * bpis_ptr, 403 const basic_pointer_iserializer * (*finder)( 404 const boost::serialization::extended_type_info & type_ 405 ) 406 407 ){ ..... 436 BOOST_ASSERT(NULL != bpis_ptr); 437 class_id_type new_cid = register_type(bpis_ptr->get_basic_serializer()); 438 int i = cid; 439 cobject_id_vector[i].bpis_ptr = bpis_ptr; 440 BOOST_ASSERT(new_cid == cid); // yikes How do people get round this issue, where old and new release of software need to co-exist ? Would it be possible to use a #define to configure use of asserts or throw ? Any help apperciated . Best regards, Ta, Avi

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