March 2010 - Boost - lists.boost.org

suggestion on assertion macros
by DE 12 Mar '10

12 Mar '10

there were a discussion recentrly about verifying arguments of assertion macros while checks are turned off i've got an idea of how to check the argument(s) and guarantee zero code size and runtime overhead suppose we have a canonical macro 'assert()' while compiling with NDEBUG macro defined it expands to nothing which may cause annoying compiler warnings (like 'var isn't referenced') assert() checks a condition i.e. the argument must be convertible to bool then we can write #define assert(cond) sizeof(cond) but to check if the arg converts to bool we can write something like #define assert(cond) sizeof(bool(cond)) which may or may not expand to some code (i.e. machine instructions) to ensure zero overhead i suggest the following scheme: #ifdef NDEBUG typename<size_t s> struct dummy_for_assert; #define my_assert(cond)\ typedef dummy_for_assert<sizeof(bool(cond))> typedef_dummy_for_assert #elif #define my_assert(cond) assert(cond) #endif i hope you got the idea by the way the typedef may be enclosed in a scope in order not to mess around: #define my_assert(cond)\ do {\ typedef dummy_for_assert<sizeof(bool(cond))> t;\ } while(false) although all this looks like a big kludge i believe more advanced programmers would make it work very well (and even make it idiomatic) if that already has been discussed sorry for wasting your time -- Pavel

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[repost][multiarray] Bug with boost::detail::multi_array::array_iterator on MSVC 2010RC?
by Jesse Perla 12 Mar '10

12 Mar '10

Sorry for the repost, but I am pretty sure this is a bug with the MSVC standard library integration to multi_array. It could also be related to boost::iterator The following code worked on MSVC 2008, Intel 11.1 on Windows, and MinGW, ... but is failing to compile on the MSVC 2010RC. I tested this against boost 1.42 and the boost trunk from SVN. #pragma warning(disable:4996) //Tough to see errors otherwise. #include <boost/multi_array.hpp> int main(int argc, char* argv[]) { boost::multi_array<double, 3> f_values(boost::extents[5][6][7]); //A boost::multidimensional object boost::detail::multi_array::sub_array<double, 2> sub_f = f_values[2]; //Works boost::multi_array<double, 2> sub_f2 = f_values[2]; //Fails on MSVC10, works on all others } ////////////////// The problem here is with the constructor in multi_array.hpp around line 334. It uses an std::copy, However, if I replace the: std::copy(rhs.begin(),rhs.end(),this->begin()); with the (godawful) direct iteration: auto p_rhs = rhs.begin(); auto p_this = this->begin(); while(p_rhs < rhs.end()) { *p_this = *p_rhs; ++p_rhs; ++p_this; } Things compile fine. Also note, that this same problem with the std::copy happens in pretty much every other constructor/place it is used in this library. (i.e. all over the place, so this 'hack' is pretty useless). It appears to me that the MSVC's STD implementation isn't finding a match a std::copy overload impl with the iterators as: Input iterator as: boost::detail::multi_array::array_iterator<double,const double *,boost::mpl::size_t<2>,boost::detail::multi_array::const_sub_array<double,1>> Output iterator as: boost::detail::multi_array::array_iterator<double,double *,boost::mpl::size_t<2>,boost::detail::multi_array::sub_array<double,1>>, I have attached my test files. Any ideas or patches would be appreciated

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How to specify Boost headers location properly
by Mateusz Loskot 11 Mar '10

11 Mar '10

Hi, I'm trying to learn what is, let's say, canonical form of configuring Boost headers location in Jamfiles of test and example programs for: 1) Libraries that live inside Boost tree (SVN trunk) - Boost libraries. 2) Libraries that are close-to-Boost, it is Sandbox, libraries being reviewed and libraries already reviewed and accepted but not yet included in Boost tree In the case 1), I assume it's required that a library is configured to use headers from the same Boost tree where it is actually included. In the case 2), I assume that it's recommended to configure a library in such way that allows compilation in two ways: a) user copies library to Boost tree and compiles, i.e. examples, by executing bjam inside BOOST_ROOT/libs/LIBRARY/example b) user does not copy library to Boost tree, but keeps it externally and still can do: cd BOOST_ROOT/libs/LIBRARY/example bjam I was explained by folks on #boost channel, that there is no requirement for user to: - set environment variables like BOOST_ROOT - or to set global <include> requirements in user-config.jam, like this: project : requirements <include>/path/to/boost/root ; As I was told, the only entry in user-config.jam related to location of Boost headers should be use-project boost : /path/to/boost/root ; I'm looking at various Jamfiles in trunk and sandbox and I'm a bit confused. For 1st example for the case 1), in trunk/libs/accumulators/example/Jamfile.v2, Boost headers are located by relative path and mysterious $(BOOST_ROOT) exe example : main.cpp : <include>../../.. <include>$(BOOST_ROOT) ; For 2nd example of the case 1), in libs/program_options/example/Jamfile.v2, there is no <include> or <source> requirement configured, so AFAIU, it means global Boost Jamroot takes care of setting headers location. For 1st example for the case 2), it is ITL library that was submitted to review, not yet in Boost tree, I see similar double-include trick in Jamfile of examples: https://svn.boost.org/svn/boost/sandbox/itl/libs/itl/example/Jamfile.v2 exe overlap_counter : overlap_counter_/overlap_counter.cpp : <include>../../.. <include>$(BOOST_ROOT) ; I have seen similar pattern for other libraries in Sandbox. It tells me that either these libraries can be build *only* from within Boost tree or, if user wants to build them from outside Boost tree, it is required to specify the mysterious BOOST_ROOT which in fact should not be required at all [1] [1] http://lists.boost.org/boost-users/2004/09/7755.php It also suggests me that for cases as the one illustrated with Jamfile from the ITL library, if a user doesn't copy a library in to Boost tree or doesn't set BOOST_ROOT or doesn't put the hack of hard-coded Boost headers path as <include> in user-config.jam file, then it is not possible to compile such library (or its examples or tests, if it's headers-only). I started to ask myself: How folks compile libraries while reviewing if these libraries are configured to locate headers with <include>../../.. <include>$(BOOST_ROOT) Does it mean a library submitted to review (or reviewed and accepted but not yet included to Boost) are required to be configured as living in Boost tree? Or, does it mean everybody makes "unofficial" configurations to environment like setting $BOOST_ROOT or hacking user-config.jam. Now, here comes final question derived from all the elaborate introduction: If I assume that a user installs Boost without making any of the not recommended hacks to his environment (let's say, only puts use-project boost directive to user-config.jam), then How should I configure Jamfiles of Boost Geometry (examples and tests) to locate Boost headers in the following two situations: 1) User copies Boost Geometry in to Boost tree and compiles examples and tests 2) User keeps Boost Geometry outside Boost tree and still should be able to compile examples and tests using his Boost installation. By the way, I have started discussing this [2] problem on Boost Geometry mailing list but there are still some confusions [3] that make this issue far from clarified. [2] http://lists.osgeo.org/pipermail/ggl/2010-March/000657.html [3] http://lists.osgeo.org/pipermail/ggl/2010-March/000662.html I'd appreciate if someone here could teach me, once and for good, how to make it right. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org

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Participation in google summer of code 2010
by vikas kushwaha 11 Mar '10

11 Mar '10

I would like to participate in gsoc 2010. I was thinking of audio library for boost, as a project. Will it be a good project to work upon. Thanks in advance.

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[Log] Review Results
by Roland Bock 11 Mar '10

11 Mar '10

Hi, here are my review results. I have organized it in two parts. A relatively short one answering the formal review questions and a second part that lists a lot of additional details. Attached is a short program which contains some of the tests I did. - Should the library be accepted? ================================= YES, but some things should be fixed first (see also details below): - Compiler warnings: I get tons of them. Zero should be the goal. - Completeness of documentation: Some things are simply missing and can only be found in the code - Compile time for the library - A lot of details are listed below. Of course, I would like to see all of them addressed, but my vote does not depend on every single one of them. - What is your evaluation of the design? ======================================== Very flexible, very modularized. I have two concerns, both explained in more detail below. a) In some aspects, it is too flexible, I think. This makes it hard to document (which can be seen in the current documentation) and hard to test (the latter is just me guessing). b) It is easy to use it in the wrong way, which leads to exceptions and lost log records, possibly after hours of running, probably in some rare and potentially critical situation. It would be better to somehow prevent the wrong usage at compile time. - What is your evaluation of the implementation? ================================================ I looked at the code only briefly, but what I saw looked good to me (see below). - What is your evaluation of the documentation? =============================================== Very nice examples, very well motivated tutorial. Good overview on details. Was good to read to get an idea of how the library can be used. But (at least for me) it was sometimes tough to combine the information given in examples to the things I want to do myself. Mostly this was because some information is missing (or too well hidden for me). I admit that I got lost on the last few pages, but that was probably due to me not actually experimenting with all of it. See below for specific remarks. - What is your evaluation of the potential usefulness of the library? ===================================================================== Very useful! Logging is one of the core aspects of almost all software. And it is not nearly as easy as it seems at first glance. Thus, it is very useful to have a well designed, well documented, well tested and well supported log library. - Did you try to use the library? With what compiler? Did you have any ====================================================================== problems? ========= I compiled the library (the version from the SVN trunk, because the packaged version from sourceforge did not compile on my system). I also did some experiments to see how easy or hard it was to transfer the information from the documentation to some "real" code. I stumbled over quite a few details, but am convinced that I could use the library, soon. The most annoying problem were the compile warnings I mentioned above. Ubuntu-8.04 64bit, gcc-4.2.4, boost-log from SVN trunk, boost-1.42 - How much effort did you put into your evaluation? A glance? A quick ===================================================================== reading? In-depth study? ======================== I spent several hours reading the documentation and several hours of experimenting (see details below), about 12 hours in total (which includes writing this review). - Are you knowledgeable about the problem domain? ================================================= I wrote the log library which is being used by some 100 components in our company for about two years now. It is based on POCO library (pocoproject.org) Before writing it, I analyzed several log other libraries too, of course. So I would not consider myself an expert, but not really a newbie, either :-) ------------------------------------------------------------------------ MORE DETAILS ------------------------------------------------------------------------ Missing Features: ================= Maybe I overlooked it, but I did not find the following: - Have several sinks share a formatter: The programs in my company typically produce several log files: - debug: Contains everything - warn: Contains everything which is at least a warning - error: Contains everything which is error or fatal Messages in all files are formatted in the same way. I understand that I could create several file sinks and each is given its own formatter. But that would mean that the same formatting is done several times. Is there a way to have several sinks with different filter but sharing the log records? Compiling: ========== - Library Code: As mentioned in an earlier mail, it takes awfully long to compile the library, which is due to one file: formatter_parser.cpp The parsing is based on Boost.Spirit (classic) and takes 20 minutes to compile on my maschine (Ubuntu-8.04 64bit, gcc-4.2.4, Intel Quad Core, 2.5GHz) I don't know how much can be gained by switching to Spirit 2.1. But I am sure a way has to be found to accelerate the compilation. Otherwise, users will do what I did: Get nervous about the long compilation time and tend to press Ctrl-C before the work is done. - My Code: All of the code in our company is compiled with the following settings (gcc-4.2.4): -Wall -Wreorder -Wnon-virtual-dtor -Wno-non-template-friend -Woverloaded-virtual -Wsign-promo -Wextra -fvisibility=hidden We strive for code that compiles without warnings, but with boost.log, I get tons of warnings. What I have seen so far should be easy to get rid of. But I will not be able to use the boost.log library unless the warnings are taken care of. Debugging: ========== - I tried to add a timestamp to each written record. I used core->add_global_attribute("TimeStamp", boost::make_shared< attrs::local_clock >()); backend->set_formatter( fmt::stream << fmt::date_time< std::tm >("TimeStamp") << ": [" << fmt::attr< severity_level >("Severity") << "] " << fmt::message() ); This compiled, but when I ran my program, I got an exception message which did not really tell what was wrong: ----------------- terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::log_mt_posix::missing_value> >' what(): Requested attribute value not found ----------------- I think, at least it should tell which attribute value was not found. But the real reason for the exception was that the types of the attribute and the attribute value did not match. - Is there a way to get to these exceptions earlier? As of now, in the example above, the exception is thrown when a logger is used. This is much too late. I need to initialize logging and then be sure that logging will work for the components that use it (within limits of course, e.g. filesystem being full). But mis-configurations like above must be detected before the real work is done in the components using the log system. For instance when constructing the logger. - Of course, best would be to prevent such stuff at compile time (no idea how, though) Design: ======= - Flexibility: To be honest, in some aspects, I would have preferred to see less flexibility, for two reasons: a) the documentation effort rises and I suspect that the missing completeness of the documentation is partly a result of over-flexibility b) the testing effort rises (I guess). It will be hard to make sure that everything works as expected. An example is log record formatting via Boost.Lamda, Boost.Format, String Templates, Custom-Formatting, which is all shown by example in the tutorial, but the detailed description of Formatters does not even mention String Templates or Custom Formatting. - Easy to misuse: If your formatter requires a severity and the logger does not add one to the log record or adds a severity of the wrong type, using that logger results in an exception, see attached code. It is unlikely that this will happen in some part of the code which is executed frequently, because the developer would certainly notice. But what if someone would add a non-matching logger at some rarely executed but critical code section? Not only would the code fail with an exception, it would also fail to log the message! As of now, I would have to provide some factory method which produces loggers for anyone who needs one. And no logger is ever to be constructed otherwise. Just to make sure that everybody uses a logger that actually produces digestible log records. I can live with that, but I do not consider it a good solution. Code Quality: ============= - Readability: I did not read through all the code, and none in very much detail, but the parts I looked at, looked well organized and readable. - Names: - namespace trivial: I admit that I don't like that, especially since its content is not exactly trivial. Easy, basic or default maybe, I don't know. But not trivial :-) Documentation: ============== Very nice examples, very well motivated tutorial. Good overview on details. Was good to read to get an idea of how the library can be used. But (at least for me) it was sometimes tough to combine the information given in examples to the things I want to do myself. I admit that I got lost on the last few pages, but was probably due to me not actually experimenting with all of it. Some things should be looked into, though: Build process: - it would be nice, if the default build configuration were documented - I wonder which build configuration will be used when the library is included in boost? Tutorial: - Trivial logging with filters: The "Tip" that streaming expressions are not evaluated if the message is filtered should probably be a warning of potential hazard. It is certainly a good feature, but the semantics of the macros are not immediately obvious so I would give the "Tip" a more critical nature. - none of the code examples is complete. They are missing the namespace declarations documented in the introduction, at least. While brevity is good, it would be very helpful to have complete, compiling examples in the tutorial Missing Documentation: - Not all include files are mentioned. This makes it unnecessarily tough to follow the examples. For instance, boost/log/utility/empty_deleter.hpp is required to use logging::empty_deleter. I could not find this information in all of the turorial and details. Another, maybe even more critical example: The BOOST_LOG macro is defined in boost/log/sources/record_ostream.hpp Again I did not find that information in the tutorial. - I understand that I can use my own set of severity levels. It is well documented how to filter messages using these severity levels. But I have no idea how to format messages with these severity levels? I do not want the number, I'd like a string, of course. I looked it up in the trivial.hpp, but it should be part of the documentation. - Maybe I missed it, but I did not find an overview of the log rotation options, including a description of the placeholders in strings. Specific question: Can I tell the log rotation to take place at midnight (regardless of the amount of data which is being logged)? I would like to stress this last item one more time: The examples are excellent, but they should be accompanied by more formal tables which show the complete set of options, e.g. which placeholders can be used in a filename format or a list of public (protected?) member functions of a logger. For instance, I found the logger::strm() member in examples only.

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[SoC] project ideas: BigInt
by Andrew Sutton 11 Mar '10

11 Mar '10

I put BigInt back on the project ideas board with a caveat that some approaches aren't viable due to licensing concerns and that successful proposals should include discussion of those concerns. Out of curiosity, do we have a summary of those licensing issues and other concerns for this project? I haven't had the time to dig through archives. If we're accepting for BigInt, should also solicit a project for arbitrary precision floats? What about a fixed point data structure? Andrew Sutton andrew.n.sutton(a)gmail.com

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[log] Review attempt
by Roland Bock 11 Mar '10

11 Mar '10

Hi, good to see that boost.log is being formally reviewed! From what I read in the documentation so far, I am really looking forward to seeing the library included in boost. I sure want to do some tests, hoping to replace our current logging system, soon, but today I can only answer the following review item: - Did you try to use the library? With what compiler? Did you have any problems? Yes, I tried and failed to compile it. Details are below. Platform: Ubuntu 8.04, 64bit, g++ 4.2.4 Intel QuadCore 2.5GHz, 8GB Ram Compilation: ============ Sounds embarassing, but I failed to compile the library. I copied the folders boost, lib and doc from boost-log-RC4 to boost_1_42_0, called ./bootstrap.sh ./bjam -d+2 --build-dir=build --with-log --prefix=/my/install/path link=shared runtime-link=shared install All looked well until this point: gcc.compile.c++ build/boost/bin.v2/libs/log/build/gcc-4.2.4/release/threading-multi/filter_parser.o "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -pthread -fPIC -fno-strict-aliasing -DBOOST_ALL_NO_LIB=1 -DBOOST_DATE_TIME_DYN_LINK=1 -DBOOST_FILESYSTEM_DYN_LINK=1 -DBOOST_LOG_DLL -DBOOST_LOG_SETUP_BUILDING_THE_LIB=1 -DBOOST_LOG_SETUP_DLL -DBOOST_LOG_USE_NATIVE_SYSLOG=1 -DBOOST_SYSTEM_DYN_LINK=1 -DBOOST_THREAD_POSIX -DBOOST_THREAD_USE_DLL=1 -DDATE_TIME_INLINE -DNDEBUG -I"." -c -o "build/boost/bin.v2/libs/log/build/gcc-4.2.4/release/threading-multi/filter_parser.o" "libs/log/src/filter_parser.cpp" The process cc1plus was running about 20 minutes (100%CPU, moderate RAM usage) before anything else happened. Then, after lots and lots of very long error messages, it continues like this: ...skipped <pbuild/boost/bin.v2/libs/log/build/gcc-4.2.4/release/threading-multi>libboost_log.so.1.42.0 for lack of <pbuild/boost/bin.v2/libs/log/build/gcc-4.2.4/release/threading-multi>attribute_set.o... Hmm. Not sure how to proceed. Should I send the whole bunch of error messages to the list as an attachment? Regards, Roland

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Summer of Code 2010
by Vladimir Prus 11 Mar '10

11 Mar '10

Folks, Google Summer of Code will continue in 2010, and I believe the organization applications will be accepted starting March 8. Are we going to participate, and if so, who is taking responsibility for submitting the application? Thanks, Volodya

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[log] Boost.Log formal review
by Ralf Globisch 11 Mar '10

11 Mar '10

Firstly, thanks for the wonderfully written library Andrey. * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Yes, definitely! The general review checklist is provided below: * What is your evaluation of the design? Good design and simple enough to use. Highly flexible and not too complex. * What is your evaluation of the implementation? Did not consider the implementation. * What is your evaluation of the documentation? Detailed documentation that details rationale, design decisions, tutorials, etc. AFAIR there was no link to the examples in the documentation, that perhaps could be added (if it isn't there already) to make it easier to get started. * What is your evaluation of the potential usefulness of the library? A logging library is a necessary debugging tool and is very useful if not neccessary in any application. A "standard" (and boost is as close to standard as it gets) logging library is long overdue. After searching extensively for a suitable logging library, I finally came across this library which satisfied all my demands. I had previously implemented my own logging library for use in a project which had specific requirements and this library met all of them and is far superior. However I should also mention that I have only recently compiled and tested the library using the provided examples as a quick guide to get going so my experience with the library is somewhat limited. * Did you try to use the library? With what compiler? Did you have any problems? Briefly, used some of the examples to get started. I would have liked to play with the library more but am submitting this review now due to limited time constraints. - Compilation: Compiled under Windows 7, Visual Studio 2008 without any problems * How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I compiled the library and built a couple of the examples, changed parameters just to get an introductory feel. By no means an in-depth study. Read through the documentation. For me most importantly, I compared the functionality of the log library to the functional requirements of a logging library I wrote for use in a commercial real time streaming system and this library met all requirements and is far more flexible and superior to my own implementation. * Are you knowledgeable about the problem domain? Somewhat, I have written my own logging library although nowhere near as extensive as this one. Also, I am fairly new to boost (started using aspects of boost less than two years ago) and from reading through this mailing list I still have a lot to learn about c++/design, etc. From a previous post about the log library: > FWIW, I consider this library to be > http://en.wikipedia.org/wiki/Data_logging > and not the database/filesystem logging stuff, > http://en.wikipedia.org/wiki/Write_ahead_logging Agreed. This library allows one to log all application-related information in a simple manner and provides an effective debugging tool. Regards, Ralf -- This message is subject to the CSIR's copyright terms and conditions, e-mail legal notice, and implemented Open Document Format (ODF) standard. The full disclaimer details can be found at http://www.csir.co.za/disclaimer.html. This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. MailScanner thanks Transtec Computers for their support.

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[SoC] [Asio] User input
by Andrew Sutton 10 Mar '10

10 Mar '10

A couple of years ago there was an SoC idea to extend Asio with user-input. This seemed like it may have been a pretty good idea. I think it would be great if, minimally, Boost provided some mechanism of interacting with a shell in raw input mode--in a well-designed and portable way, of course :) Did any work actually occur in this direction? Does it still seem like a viable SoC project? Would anybody be willing to mentor it? Andrew Sutton andrew.n.sutton(a)gmail.com

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