November 2011 - Boost - lists.preview.boost.org

Re: [boost] [optional] std::tr2::optional
by Andrzej Krzemienski 19 Nov '11

19 Nov '11

> > 3. T is neither copyable nor moveable -- it is like a scope guard, or > > boost::scoped_ptr. In this case optional<T> still provides assignment by > > making a "pseudo destructor call" followed by a call to placement new. -- > > but this gives only basic guarantee. > The guarantee is strong if the placement delete/new are marked > noexcept, isn't it? What I meant by "a >>pseudo destructor call<< followed by a call to placement new." is a call to destructor w/o releasing the memory and then a call to constructor w/o allocating memory: ob.~T(); new (&ob) T( std::forward<Args>(args)... ); This trick will provide a strong guarantee if destructor and the constructor are nothrow. While destructors usually are non-throwing, it is rather unlikely that constructors would not throw: it is the constructors that we often expect to throw in case of initialization failure. Regards, &rzej

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[inteprocess] Using named_mutex on Windows 7
by Edward Diener 19 Nov '11

19 Nov '11

I wrote a program more than 3 years ago where I used boost::interprocess_named_mutex to protect more than one instance of the same process from running the same sequence of code at the same time. The program appears to run fine under Windows XP and Windows Vista but occasionally locks up waiting for the locked mutex to unlock on Windows 7. The code looks like this: ------------------------------------------------------------------- boost::interprocess::named_mutex cmutex(boost::interprocess::open_or_create_t(),"MyMutexName"); { boost::interprocess::scoped_lock<boost::interprocess::named_mutex> cscoped(cmutex); // Code here which must be run one at a time. } ------------------------------------------------------------------- Under Windows 7 the code occasionally hangs on the scoped_lock instantiation, which of course I can not have. I notice there is a file in the temporary directory ( TMP or TEMP environment variable ) which is being used by interprocess, and after that file is manually deleted, the program no longer hangs on the scoped_lock instantiation. Is there a reason for this problem on Windows 7 ? I know that Windows 7 has global and local named mutexes and only by prefacing a named mutex name with global\ is the mutex truly global. I do not know if this is causing the problem on Windows 7. It does seem as if something in the file in the temporary directory is telling inteprocess that "MyMutexName" is still locked when the hangup occurs, but I would have expected that when acoped_lock goes out of scope, it handles resetting that file to the correct state. I wonder if this has something to do with UAC/file permissions in Windows 7, where the process somehow can no longer write to the file in the temporary directory afte creating it. Is this a known interprocess problem, perhaps fixed in a later release ? I wrote my code before Windows 7 even came out, recompiled it for Windows 7, but did not update the version of Boost I was using for the program ( Boost 1.35 ). Maybe I need to do that ? I would certainly be willing to do that if I knew that this was a problem with interprocess in Boost 1.35 that has subsequently been fixed in a later version of Boost.

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[signals] Compiler error
by "Claas H. Köhler" 18 Nov '11

18 Nov '11

Hi everybody! When compiling boost 1.48.0 using gcc-4.6 and the "--std=c+0x" option, I get the following error message: libs/signals/src/named_slot_map.cpp: In member function ‘void boost::signals::detail::named_slot_map::disconnect(const boost::signals::detail::stored_group&)’: libs/signals/src/named_slot_map.cpp:99:48: error: conversion from ‘std::list<boost::signals::detail::connection_slot_pair>::const_iterator {aka std::_List_const_iterator<boost::signals::detail::connection_slot_pair>}’ to non-scalar type ‘boost::signals::detail::slot_pair_iterator {aka std::_List_iterator<boost::signals::detail::connection_slot_pair>}’ requested The reason seems to be that std::map's erase function expects a std::map::iterator in the old standard (according to cplusplus.com) while c++11 seemingly requires a std::map::const_iterator as argument (see section 23.4.4.1). Thus replacing line 105 OLD groups.erase(group); NEW groups.erase( static_cast<const_group_iterator>(group) ); and line 128 OLD if (empty(g)) groups.erase(g++); NEW if (empty(g)) groups.erase( static_cast<const_group_iterator>(g++); solves the problem for me. Is it intended to have all boost libraries conforming with C++11? Regards Claas

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date_time using CPU performance counter
by Kenneth Porter 18 Nov '11

18 Nov '11

I need high precision under Windows XP but don't need long-term date accuracy. To that end, I think it would be useful to have a microsec_clock implemented in terms of the Windows QueryPerformanceCounter API (which wraps a CPU register query) instead of the GetSystemTimeAsFileTime API (which is only good to 15 msecs and almost guarantees a context switch). Has anyone attempted this? How hard is it to code up a new clock source to fit into the Boost date_time design?

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multi_array and concept check
by Ivan Sorokin 17 Nov '11

17 Nov '11

Hello! Currently it is not possible to pass shape() of one multi_array into constuctor of another: boost::multi_array<float, 2> a; boost::multi_array<float, 2> b(a.shape()); This is because shape() returns size_t const* and multi_array check in constructor that ExtendList satisfy CollectionConcept. size_t const* don't satisfy this concept. I'm going to allow constructor of multi_array to get both size_t const* and size_t const[]. So I'm going to replace extents.begin() with boost::begin(extents). What should I do with concept check?

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Boost.Local Review
by Pierre Morcello 17 Nov '11

17 Nov '11

Hello Boost community, Here is my review of the local function library. - What is your evaluation of the design? The design is clear. Several iterations were done already to come to what it is today. Of course no one is particularly fond of macros, but a huge work was done to reduce the potential problems and on the other hand the library can really help a lot. - What is your evaluation of the implementation? I did not get too much into the current implementation. I dug it almost one year ago, but there were changes since then. The implementation is correct given the features of the library (use of 'this', functor,, name,...). If there were less features, then some optimisations would have been possible (example : not use a virtual function, not use a functor). But the library would in that case have fewer cases of use. I know how the first verion of Lorenzo worked but I did not check the latest. Given the current features, I don't see how to do even better than what Lorenzo did. So I am happy with the implementation. - What is your evaluation of the documentation? I really appreciate the detailled documentation. On a 'merchandising note', the first page is too big. I think this could 'afraid' some new readers. Introduction + an 8-line motivating example should be enough to appeal (or not) the new reader. I am happy to review a submitted library with a complete documentation (that does not always happen). - What is your evaluation of the potential usefulness of the library? This library is filling a few strong needs. Several users including myself needed local function and const block. I am lazy when it comes to functors, I also find this library is pretty nice to make them quick. C++11 will on that last part change it , but const block are a must have in my opinion which are not available in C++11. The local function can greatly reduce the presence of internal functions in ".h", and thus make the interfaces much better in some cases. - Did you try to use the library? With what compiler? Did you have any problems? I use regularly this library on VC9, but mostly for local function. As I don't try to push the limits, I did not come into problems. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I have followed Lorenzo work since his proposition. At the beginning I followed it much more closely, but right now I dont' have the time to redo an in depth study. I use a previous version of Lorenzo library regularly. So for the review, I simply had a glance. But I already read the documentation in detail several month ago. - Are you knowledgeable about the problem domain? I implemented a my own version of local functions for boost almost 2 years ago I think. - Boost.Local's local exits provide the same functionality (and then some) as Boost.ScopeExit. Does this duplication of functionality need to be dealt with, and if so, how? I think it's important to check if the author are ok with merging or not. Obviously Lorenzo is very motivated and gives great feedback on his works with boost. Just make sure this won't hurt his motivation ? Because then there are the question of maintening the libraries which is not always the easiest. I am ok if one replace the other. - Do you vote for the library? Yes, I vote for its admission. I also want to add that I am amazed by the overall results in term of quality that Lorenzo was able to get with this library. Lorenzo is constently gathering the users needs and updating his library in that way. Like a marathonian. Very inspiring! Best regards, Pierre Morcello -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-Local-Review-tp4078276p4078276.html Sent from the Boost - Dev mailing list archive at Nabble.com.

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[context] update
by Oliver Kowalke 17 Nov '11

17 Nov '11

Hi, a new updated version is available. src: http://github.com/olk/boost.context docu: http://ok73.ok.funpic.de/boost/libs/context/doc/html/index.html next step mini-review? so long, Oliver

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Boost.Local Review (Nov 10, 2011 to Nov 19, 2011)
by Jeffrey Lee Hellrung, Jr. 17 Nov '11

17 Nov '11

Hi all, It is time! The review of Lorenzo Caminiti's proposed Boost.Local library begins tomorrow, ***November 10, 2011***, and ends on ***November 19, 2011***. Boost.Local implements local functions, local blocks, and local exits for the C++ programming language. It allows one to define a function at any declarative scope, including function scope; bind variables from the enclosing scope; and pass this function to templated STL-style algorithms. Please see the Introduction of the documentation for a longer but still brief overview. -------- The code and documentation are available from the Boost sandbox ( https://svn.boost.org/svn/boost/sandbox/) https://svn.boost.org/svn/boost/sandbox/local/ [everything] https://svn.boost.org/svn/boost/sandbox/local/boost/ [code] https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/index.htm… -------- Please state clearly whether you think this library should be accepted as a Boost library. Other questions you may want to consider: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Please also consider the following issues and proposals specific to Boost.Local. Your opinion is welcome on any or all of these. - Boost.Local's local exits provide the same functionality (and then some) as Boost.ScopeExit. Does this duplication of functionality need to be dealt with, and if so, how? - Lorenzo is proposing to add boost::local::function::overload to Boost.Function as boost::function::overload. See https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost/loc… - Lorenzo is proposing to add BOOST_IDENTITY_TYPE to boost/utility. See https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_IDE… - Likewise, Lorenzo is proposing to add BOOST_IDENTITY_VALUE to boost/utility. See https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_IDE… -------- Lastly, please note that Boost.Local has included a copy of the Variadic Macro Data (VMD) library in boost/detail/preprocessor/variadic_macro_data. Since then, VMD has been modified and integrated into Boost.Preprocessor. After the review has concluded, Lorenzo will remove this local copy of the VMD library and replace its usage within Boost.Local with the Boost.Preprocessor variadic extensions. -------- Thanks in advance to all who participate in the review discussion; I'm looking forward to it! - Jeffrey Hellrung (Review Manager) - Gregory Crosswhite (Review Assistant)

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Alternative implementation for BOOST_PP_VARIADIC_SIZE
by Gennadiy Rozental 17 Nov '11

17 Nov '11

Hi, Current implementation of subject macro have a very serious shortcoming - it does not work for empty __VA_ARGS__. After googling around a bit for some ideas I came up with the following alternative: #include <boost/preprocessor/arithmetic/mul.hpp> #include <boost/preprocessor/arithmetic/sub.hpp> #include <boost/preprocessor/punctuation/comma.hpp> #define MY_VA_ARG_N( \ _1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \ _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \ _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \ _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \ _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \ _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \ _61,_62,_63, N, ...) N #define MY_VA_RSEQ_N() \ 63,62,61,60, \ 59,58,57,56,55,54,53,52,51,50, \ 49,48,47,46,45,44,43,42,41,40, \ 39,38,37,36,35,34,33,32,31,30, \ 29,28,27,26,25,24,23,22,21,20, \ 19,18,17,16,15,14,13,12,11,10, \ 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 #define MY_DO_VA_NARG2(...) MY_VA_ARG_N __VA_ARGS__ #define MY_DO_VA_NARG(...) MY_DO_VA_NARG2(( __VA_ARGS__ )) // this version produces incorrect value (1) for empty __VA_ARGS__ #define MY_VA_NARG_(...) MY_DO_VA_NARG(__VA_ARGS__, MY_VA_RSEQ_N()) // this version fixes it #define MY_VA_NARG(...) BOOST_PP_SUB( BOOST_PP_MUL( MY_VA_NARG_( __VA_ARGS__ ), 2 ), MY_VA_NARG_( BOOST_PP_COMMA __VA_ARGS__ () ) ) This version work for zero sized __VA_ARGS__ and also works for MSVC-9,10 , gcc-4.1 gcc 3.2 (did not test with other compilers). Does it make sense to improve trunk version? Regards, Gennadiy

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[1.48.0] Can't build any PDF docs
by John Maddock 16 Nov '11

16 Nov '11

I'm trying to build the PDF docs for 1.48 but all attempts to build PDF's on both Trunk and release branches fails with errors such as: bjam pdf M:/data/boost/trunk/tools/build/v2/tools\boostbook.jam:649: in object(boostbook-generator)(a)49.run from module object(boostbook-generator)@49 error: Cannot build documentation type 'pdf' M:/data/boost/trunk/tools/build/v2/build\generators.jam:1004: in try-one-generator-really from module generators M:/data/boost/trunk/tools/build/v2/build\generators.jam:1066: in try-one-generator from module generators M:/data/boost/trunk/tools/build/v2/build\generators.jam:1282: in construct-really from module generators M:/data/boost/trunk/tools/build/v2/build\generators.jam:1366: in generators.construct from module generators M:/data/boost/trunk/tools/build/v2/build\targets.jam:1495: in construct from module object(typed-target)@776 M:/data/boost/trunk/tools/build/v2/build\targets.jam:1297: in object(typed-target)(a)776.generate from module object(typed-target)@776 M:/data/boost/trunk/tools/build/v2/build\targets.jam:732: in generate-really from module object(main-target)@782 M:/data/boost/trunk/tools/build/v2/build\targets.jam:704: in object(main-target)(a)782.generate from module object(main-target)@782 M:/data/boost/trunk/tools/build/v2/build\targets.jam:258: in object(project-target)(a)772.generate from module object(project-target)@772 M:/data/boost/trunk/tools/build/v2\build-system.jam:736: in load from module build-system M:\data\boost\trunk\tools\build\v2/kernel\modules.jam:283: in import from module modules M:\data\boost\trunk\tools\build\v2\kernel\bootstrap.jam:142: in boost-build from module M:\data\boost\trunk\boost-build.jam:17: in module scope from module Nothing has changed in my user-config.jam, and I've updated to the latest bjam executable. Any ideas on what broke? Thanks, John.

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Boost.Random.uniform_01 gives different number sequence in Boost 1.37 and Boost 1.45
by Martin.Sovik＠Emerson.com 16 Nov '11

16 Nov '11

Hi. It seems that uniform_01 generates different number sequences in version 1.37 and 1.45 Is this intentional, or is it a bug? This short program #include <iostream> #include "boost/random/mersenne_twister.hpp" #include "boost/random/uniform_01.hpp" int main() { boost::mt19937 random_generator(4315); boost::uniform_01< boost::mt19937, double > uniform_generator(random_generator); std::cout<<"Generating uniform distribution using Boost 1.45"<<std::endl; for (int i=0; i<10;++i) { std::cout<<uniform_generator()<<std::endl; } return 0; } Compiled with the two versions, gives the respective output: D:\dev\test_bed>uniform_dist_boost_1_37 Generating uniform distribution using Boost 1.37 0.239136 0.920749 0.889477 0.208172 0.169688 0.636659 0.78322 0.915117 0.25697 0.358218 D:\dev\\test_bed>uniform_dist_boost_1_45 Generating uniform distribution using Boost 1.45 0.306389 0.511291 0.496429 0.156168 0.910315 0.644836 0.331514 0.558632 0.723934 0.998796 As far as I can tell, Boost.mt19937 gives the same number sequence in both cases, but the output from Boost.uniform_01 differs. This topic has been briefly touched in the thread [boost] Random numbers question<154235.php> Anant Rao (2009-07-24 18:47:31) Where it seems like Rao got different numbers even between Boost 1.38 and Boost 1.39 We use Boost 1.37 in the previous release of our software, and Boost 1.45 in the current, and we have received a bug report from one of our clients that our current release has different behaviour. Is there any way to fix this, other than use the 1.37 version of Boost.uniform_01? Thanks, Martin Søvik

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Re: [boost] [1.48.0] Release candidates available
by Tom Kent 16 Nov '11

16 Nov '11

> Release candidate files for 1.48.0 are available at http://boost.cowic.de/rc/ > > md5sum on the originals: > > 7dd95e71c43ddd35997d9f2346e7f567 *boost_1_48_0.7z > d1e9a7a7f532bb031a3c175d86688d95 *boost_1_48_0.tar.bz2 > 313a11e97eb56eb7efd18325354631be *boost_1_48_0.tar.gz > b08fda829eec96b4f1071ce2ea6831f5 *boost_1_48_0.zip > > As always, the release managers would appreciate it if you download > the candidate of your choice and give building it a try. Please report > both success and failure, and anything else that is noteworthy. > > This helps ensure the candidates build OK before we push them out to > SourceForge. > > Thanks, > > --The release managers On a windows 7 - 32 bit VM, I built: msvc-8.0 msvc-8.0 - address-model=64 msvc-9.0 msvc-9.0 - address-model=64 msvc-10.0 msvc-10.0 - address-model=64 All builds were successful. I was able to smoothly link and run with the binaries on windows 7 32 or 64 (depending on the library build). Tom Kent

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[program_options] Improving error text in exceptions
by Leo Goodstadt 16 Nov '11

16 Nov '11

On 15 November 2011 09:08, Vladimir Prus <vladimir(a)codesourcery.com wrote: > > Leo Goodstadt wrote: > > I would very much like to make the error messages in program_options > > exceptions more consistent and informative. > > I've looked over the error messages you have proposed, and I think it's > an overall improvement. I would appreciate patch to make this change. > Thanks! Cool. Will do that. The error messages meant for programmers I shall leave alone. This exercise is so tedious that I doubt anyone else is going to do more than tinker with the message text so I am keen to do an exhaustive job. As I mentioned, for command line messages, <option '--foo_bar' is ambiguous> seems much clearer than than <option 'foo_bar' is ambiguous>. However, it would be inappropriate to add "--" to config file and dos style options. The easiest thing would be to add a "prefix" parameter to the set_option_name() functions in errors.hpp These are called inside store() in variables_map.cpp. To add "--" or "/" prefixes as appropriate, is it sufficient to look at basic_option::original_tokens and basic_option::string_key? A) Use no prefix if original_tokens[0] is unprefixed, B) Use the parsed prefix (original_tokens[0]) if basic_option::string_key.length() = 1 C) Prefer "--" for long option names The same logic would apply to 1) exceptions thrown from cmdline::finish_option() in cmdline.cpp 2) options_description::find() (in options_description.cpp) called from store() (in variables_map.cpp) 3) options_description::find_nothrow() (in options_description.cpp) called from cmdline::run(), cmdline::finish_option(), parse_short_option(), and parse_disguised_long_option() (in cmdline.cpp) (Despite its name, find_nothrow() can throw()!) The difficult case is supporting the correct prefix for "required_option" in variables_map::notify() (variables_map.cpp). I propose that where missing options can be specified in both configuration file and on the command line, the command line should take precedence, and "--option_name" displayed in the error message. To support this, "basic_parsed_options" needs an extra prefix field, which would be set appropriately by basic_command_line_parser<charT>::run(). Does this make sense? Thanks, Leo -- Leo Goodstadt University of Oxford, UK

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[1.48.0] Release candidates available
by Beman Dawes 16 Nov '11

16 Nov '11

Release candidate files for 1.48.0 are available at http://boost.cowic.de/rc/ md5sum on the originals: 7dd95e71c43ddd35997d9f2346e7f567 *boost_1_48_0.7z d1e9a7a7f532bb031a3c175d86688d95 *boost_1_48_0.tar.bz2 313a11e97eb56eb7efd18325354631be *boost_1_48_0.tar.gz b08fda829eec96b4f1071ce2ea6831f5 *boost_1_48_0.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. This helps ensure the candidates build OK before we push them out to SourceForge. Thanks, --The release managers

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Re: [boost] Boost.Local Review - comments by Andrzej
by Andrzej Krzemienski 15 Nov '11

15 Nov '11

> > One suggestion for the future, although I am not sure how useful it would > > turn out in practice is to have something like local expression, or even > > not necessarily a local one. This would be a function whose body consists > > of a single expression. The benefit you get is that the programmer does not > > need to specify a return type for it (you can use BOOST_TYPEOF for that), > > or doesn't even have to type keyword 'return', but this may be too much off > > topic. > Can you clarify with an example? In C++11 lambdas do not require specifying the return type, provided that the body of the function is a single return statement: because it is easy to deduce the type from such single return statement. Similarly, for Boost.Local if a function body consists of a single return statement you could (I guess) provide a more simple syntax. Instead of BOOST_TYPEOF(sum) & BOOST_LOCAL_FUNCTION_PARAMS( double num, const bind factor, bind& sum ) { return sum += factor * num; } BOOST_LOCAL_FUNCTION_NAME(add); I could write: BOOST_LOCAL_EXPRESSION_PARAMS( double num, const bind factor, bind& sum ) BOOST_LOCAL_EXPRESSION_END( add, sum += factor * num ); You save me typing the return type and 'return' keyword. But now that I have written it down I do not think it is particularly useful. > I think in a nutshell the conclusion (which I will detail in the rest > of my comments below) was that Boost.Local is handy but on compilers > with C++11 lambdas you'd just use lambdas. At the same time, > Boost.Local allows you to write local functions that work also on > C++03 compilers and that have the same compile-time and run-time > performances of lambdas on C++11 compilers. So the /main/ audience > would be someone (like myself) that wants to do local function stuff > and expects lambda-like performances on C++11 but also has to deal > with C++03 compilers. There are other benefits like const& binding > which is not supported by C++11 lambdas (so how can I bind by const a > variable that has a very expensive copy constructor using C++11 > lambdas?) and improve scope exit (i.e., local exit) but these other > benefits are probably minor in the general domain (they can be very > important or even essential is a specific and narrow domain like > Contract Programming but not critical in the general case). OK Lorenzo, I am convinced. Can we trade? I will vote 'yes', and you will add a motivation section in the documentation which will stress that the primary motivation of the library is to provide a uniform (in terms of syntax) support for local functions: fast and 'native' for C++11 compilers, and acceptable (using tricks) in older compilers. The library can be used directly or be a foundation for higher level libraries like Boost.Concept. Review Managers, I am not really trading, I vote YES for the Boost.Local and just request the motivation section in the documentation. I think the situation of Boost.Local is similar to that of Boost.Move, and the latter was accepted into Boost. Also, having a library in Boost whose primary purpose is to serve as the foundation for other Boost libraries is not a precedent (I mean Boost.Proto and now Boost.Context). Regards, &rzej

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Re: [boost] Boost.Local Review - comments by Andrzej
by Andrzej Krzemienski 15 Nov '11

15 Nov '11

Just one more thought. I was not participating in the design discussion for Boost.Local when it was probably a better time to mention this. So I am just mentioning it for reference. Functions that take parameters and bind existing objects are called closures: http://en.wikipedia.org/wiki/Closure_%28computer_science%29.<http://en.wikipedia.org/wiki/Closure_%28computer_science%29> This could have been an alternative name for BOOST_LOCAL_FUNCTION: BOOST_SCOPE_CLOSURE... Regards, &rzej

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[1.48.0] Status?
by Beman Dawes 15 Nov '11

15 Nov '11

Are there any 1.48.0 showstoppers outstanding? We are scheduled to release right now. There are still a lot of release branch regression test failures. It is very uncomfortable to see failures for popular compilers such as VC++ 10 and GCC: accumulators (most or all compilers) assign flyweight (most or all compilers) graph ublas pool (all Windows compilers) ptr_container (most or all compilers) python spirit/repository (most or all compilers) tr1 (most or all compilers) wave (all Windows compilers) See http://beta.boost.org/development/tests/release/developer/summary.html Do we really want to release with this many failures? Worried, --Beman

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[property_tree] Assign and Lua parser
by Renato Florentino Garcia 15 Nov '11

15 Nov '11

In my use of Boost Property Tree library I have coded some extensions, which are in a GitHub repository (http://github.com/renatoGarcia/boost-extensions) I would like to know if there are any interest in make any of then part of Boost Property Tree itself, probably after a suggest improvement. The more useful in my view is a Boost Assign Property Tree alike. Code: http://github.com/renatoGarcia/boost-extensions/blob/master/property_tree/i… For instance, to build in C++ code a ptree like: key1 value1 key2 { key3 12345 { key4 "value4 with spaces" } key5 value5 "" 10 "" 11 "" 12 } Instead the current: ptree pt; pt.add("key1", "value1"); ptree tmpPt1; tmpPt1.add("key3", 12345); ptree tmpPt2; tmpPt2.add("key4", "value4 with spaces"); tmpPt1.push_back(std::make_pair("", tmpPt2)); tmpPt1.add("key5", "value5"); ptree tmpPt3; tmpPt3.put_value(10); tmpPt1.push_back(std::make_pair("", tmpPt3)); ptree tmpPt4; tmpPt4.put_value(11); tmpPt1.push_back(std::make_pair("", tmpPt4)); ptree tmpPt5; tmpPt5.put_value(12); tmpPt1.push_back(std::make_pair("", tmpPt5)); pt.add_child("key2", tmpPt1); Would be a code like: ptree pt = tree() ("key1", "value1") ("key2", tree() ("key3", 12345) (tree() ("key4", "value4 with spaces")) ("key5", "value5") (10)(11)(12)); Another extension is a Lua parser, like the XML or JSON. But in this case I don't think that is desirable include it in the Boost, because of the needed of Lua libraries (at least not in a mandatory way). Code: http://github.com/renatoGarcia/boost-extensions/blob/master/property_tree/i… Regards, Renato Garcia

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Boost.Local Review - comments by Andrzej
by Andrzej Krzemienski 15 Nov '11

15 Nov '11

Hi Lorenzo, I would like to provide some comments on Boost.Local. > Please state clearly whether you think this library should be accepted > as a Boost library. I am unable to give a yes/no answer. This is mostly because I am not clear who is the intended audience of the library. I explain this in detail below. I am impressed with the library documentation. It is very informative with lots of examples, benchmarks, comparisons, rationale, and layered design (overview, and then details). This is how a Boost library's documentation (and every documentation, IMO) should look like. Yet, one thing that I am missing is what practical problems (that are not already solved) this library is trying to solve. I am not saying that it doesn't solve any. I am just saying I cannot figure it out. A typical story for a Boost library is that there is a common problem that many developers face fairly often, and at some point someone decides to fix this problem comprehensively and ultimately. This is the impression that I had, for example, with Boost.Optional. When I read about it I thought "Yes! This is what I was missing for a long time". I cannot see this in Boost.Local. Perhaps I am not the intended audience of the library, but it would help me if it was clear who the audience is. (I provide examples of what I mean below.) Documentation clearly separates three parts: local functions, local scopes and local exits. Also my impression is different on the three parts. This suggests to me that they could be three separate libraries. What do they have in common? The syntax, I guess. And the fact that you declare them inside functions. But is that enough to bundle them together? Consequently, I divide my comments into three parts. LOCAL FUNCTIONS Why would I want to use it? Personally, I have one compiler that does support local classes as template parameters. All my other compilers support lambdas. So I guess local functions are not for me. So who will use them? Someone that does not have too new compiler (because they have superior - in terms of performance - alternatives: lambdas, local classes). Someone that does not have a too old compiler, because we read in the documentation that "The implementation of this library uses preprocessor and template metaprogramming (as supported by Boost.Preprocessor<http://www.boost.org/doc/libs/release/libs/preprocessor/doc/index.html>and Boost.MPL <http://www.boost.org/doc/libs/release/libs/mpl/doc/index.html>), templates with partial specializations and function pointers (similarly to Boost.Function<http://www.boost.org/doc/libs/release/doc/html/function.html>). As a consequence, this library is fairly demanding on compilers' compliance with the C++03 <http://www.open-std.org/JTC1/SC22/WG21/docs/standards>standard." Further someone who does not mind compile-time and run-time performance overhead. And someone,who prefers the new syntax to creating a functor class non-locally. I am not sure how many users that would be? The documentation mentions proposal N2511<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2511.html>, which says that even though with lambdas and local classes we already have a good tool, we still want to have a normal function syntax for local functions. Boost.LocalFunction does not enable a normal function syntax either, so it is no better an alternative than lambdas or local classes. Except for "const binding" which I find hard to appreciate. And except for compilers that don't support C++11 features, but than again, working only with the new compilers I may not be the right person to review the library. Is this supposed to provide a seamless migration of the code from compilers w/o lambdas to those that do support lambdas? I am not comfortable with the syntax: we first specify parameters, then function body and last, we specify the function name. I am not comfortable that the other Lorenzo's library (that I await impatiently) - Boost.Contract - will provide a different function syntax than Local Functions. This will render the situation where every library will require of me to learn different function declaration syntax. On the other hand, the documentation clearly says why this syntax is necessary, so I am not saying "change the syntax". I am suspicious about the local function overloading. While I can imagine writing a local function; writing a bunch of them inside another function would be likely be some error in my design. LOCAL BLOCKS Again, why would I need them? The example with assertion does not convince me. That is, I face the practical tradeoff: additional enforcement on assertions at the cost of slower build, slower execution time and less readable syntax. I will choose not to use the blocks. The only application that I can think of is a "temporary usage" while refactoring. If I work with the code where functions are 1000-line-long, I would like to divide them into blocks and check which parts reference what variables. In this case, as one of the footnotes in documentation suggests, allowing "return;" inside blocks would be a dangerous thing. But again, if I had a luxury of lambdas, I would choose lambdas for that purpose, because they allow specifying the default binding ( [&], [=] ). It looks like local blocks are only a syntax sugar over local functions. Am I right? LOCAL EXITS While exception specifications for locals blocks seam strange, I find allowing exception specifications for local exits an error. Local exits should be subject to the same restrictions as destructors (they are implemented as destructor calls anyways): you must not throw from them. And I expect the library documentation to say it explicitly. I find this "warning" missing from Boost.ScopeExit. So I suggest to disallow (if possible) specifying exceptions in local exit, and adding a section in documentation that warns against potential throws from an exit. I do not see anything against having two libraries for the same purpose. This is pretty much the same what we already have in Boost in case of state machines. But since we have two, it is useful to ask why I would choose local exit over scope exit. My answer is: 1. Local Exit allows me to specify an empty parameter list (I cannot do it with ScopeExit). - this is a practical problem I faced 2. I can bind to "this". I do not find const binding a practical advantage. Typically for short functions it is hardly a real problem that I confuse = with ==. And exits would typically be one-liners in my code. On the other hand there are reasons why I would prefer ScopeExit to LocalExit: it spells shorter. In LocalExit I have to type word 'bind' for every single parameter even though it is obvious I need to bind them all (because scope guards do not accept normal parameters). The same argument goes for blocks, obviously. I also like ScopeExit's potential to be implemented with lambdas, which might result in performance benefits, and allow the 'default binding'. On the other hand LocalExit cannot be implemented with a lambda, if not for any other reason, then due to the const binding. It is really nice that i can bind to variable of the name 'bind'; although I cannot use type 'bind' in local functions. GENERAL THOUGHTS I am really impressed with the usage of macros. It looks like thanks to Lorenzo we are reaching a new level of preprocessor programming. Who knows how far we can go. I do not think they are overused, given the difficult task. On the other hand, error messages that I encountered give me no clue on what I have typed wrong. Decsriptions in the documentation, and the rationale clearly indicates the very detailed knowledge of many C++ aspects. One suggestion for the future, although I am not sure how useful it would turn out in practice is to have something like local expression, or even not necessarily a local one. This would be a function whose body consists of a single expression. The benefit you get is that the programmer does not need to specify a return type for it (you can use BOOST_TYPEOF for that), or doesn't even have to type keyword 'return', but this may be too much off topic. Term 'C99 <http://www.open-std.org/jtc1/sc22/wg14/www/projects#9899> and later compilers' may be a bit of an overuse for C++ compilers. I suggest 'compilers supporting variadic macros'. Also, in reply to particular review questions: > What is your evaluation of the design? It is clear. Some macros are difficult to read, e.g. Function arguments first, function name second, but I guess this is a necessity given the domain. > What is your evaluation of the implementation? The impressive macro magic is beyond my cognitive capabilities > What is your evaluation of the documentation? It is very good. It meets Boost's and my personal criteria for a good documentation. > What is your evaluation of the potential usefulness of the library? > Are you knowledgeable about the problem domain? This is the part where I have problems. I am not sure about the scope and intended audience of the library. > Did you try to use the library? With what compiler? Did you have any problems? I tried to use the library (basic examples) with VC++8 and VC++10 and Boost 1.42. I found that it does not compile if I use compiler option /ZI (Debug Information Format: Program Database for Edit & Continue) on either compiler. > How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I spent one evening on reading the documentation and playing with the basic examples. For the last remark, I believe that the criterion for accepting or rejecting a library is that if it addresses a real-life problems and if it is well designed. Boost.Local is well designed, but the intended audience and primary motivation is not clearly stated, so I find it hard to assess if the first criterion is met. All in all, Boost.Local is an impressive piece of work. Regards, &rzej

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Determining interest: C++11 parser generator library
by Gene Bushuyev 15 Nov '11

15 Nov '11

Sorry if it turns out to be a duplicate, it looks my original post was lost in cyberspace, so I'm re-posting this request. I'm trying to determine if there is a sufficient interest for including AXE C++11 recursive descent parser generator library in Boost. The zipped sources and documentation are here: http://www.gbresearch.com/axe/axe.zip - Gene Bushuyev

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[program_options] Improving error text in exceptions
by Leo Goodstadt 15 Nov '11

15 Nov '11

As a long time fan of boost::program_options, I would very much like to make the error messages in program_options exceptions more consistent and informative. Exception text is usually aimed at the developer as a diagnostic for rare errors. If the exception needs to be propagated to the end-user, it can be caught, and a more appropriate message substituted. This is not true for program_options: Exceptions from invalid program arguments are the common (and normal) reason for early program termination. It would be nice if, out of the box, exception text could be clear enough to present to the end user more or less as is. This would allow a single try/catch(exception) in main() cerr << "Error: " << e.what() << "\n"; return 1; >From the attached list of error messages, there are many, many different exception types which are thrown. The usual practice of repackaging / reformatting exceptions to be more user-friendly would be tedious or impractical. I grep-ed "boost::throw_exception" to get a list of all the exceptions and messages. I suggested revisions for all but 5. These I have set them aside at the end. I have modelled some of the proposed text on GNU genparse examples (i.e. the behaviour of "ls" and "cat" etc.). These, by dint of their frequent use / hammering by the huge linux user base, are probably good examples of the sort of friendlier clarity I would hope for. In some cases, I have tried to understand the exception text from the code but might have misunderstood the original intent. If this is useful, I shall painstaking go through the code and submit a patch. Leo Goodstadt P.S. I realise there are pitfalls to do with option prefix styles "--" and "/" but the addition of option prefixes to the exception text makes the message a lot clearer. P.P.S. I have kept the current style of starting the text in lower case even though my own preference would be for a capitalised sentence ending in a full stop. ======================================================= Original (CURRENT) and revised (CHANGED) text resulting from exception.what() ======================================================= CURRENT: <ambiguous option option_name> CHANGED: <option '--option_name' is ambiguous and matches options "--aa"," --b" and "--c".> // abbreviated instead of long/short because // length might imply too many/few letters CURRENT: <style disallows parameters for long options> CHANGED: <arguments are not allowed for unabbreviated option names> CURRENT: <style disallows parameters for short options> CHANGED: <arguments are not allowed for abbreviated option names> CURRENT: <style disallows all characters for short options> CHANGED: <abbreviated option names are not valid> CURRENT: <adjacent parameter is empty> CHANGED: <Invalid command line syntax: each option with an equal sign must be followed immediately by its argument.> CURRENT: <parameters adjacent to long options not allowed> CHANGED: <arguments are not allowed for unabbreviated options> CURRENT: <required parameter is missing in 'option_name'> CHANGED: <option '--option_name' requires an argument> CURRENT: <in option 'option_name': invalid option value> CHANGED: <invalid argument for option '--option_name'> CURRENT: <unrecognised line in 'DODGY LINE'> CHANGED: <options configuration file contained an invalid line: 'DODGY LINE'> CURRENT: <multiple occurrences> CHANGED: <option '--option_name' cannot be specified more than once> CURRENT: <can not read file NON_EXISTENT_FILE_NAME> CHANGED: <cannot read options configuration file 'FILE_NAME'> CURRENT: <missing required option required_option> CHANGED: <option '--option_name' is required> CURRENT: <too many positional options> CHANGED: <too many positional arguments have been specified> CURRENT: <unknown option unknown_option> CHANGED: <unrecognised option 'option_name'> CURRENT: <in option 'invalid_option': invalid bool value> CHANGED: <at least one argument is required for option '--option_name> CURRENT: <in option 'option_name': invalid bool value> CHANGED: <invalid argument for option '--option_name'. Valid arguments are 'on|off', 'yes|no', '1|0' and 'true|false'> CURRENT: <in option 'option_name': multiple values not allowed> CHANGED: <option '--option_name' only takes a single argument> Not sure what these mean and have left them alone. libs/program_options/src/parsers.cpp:112: boost::throw_exception(error("long name required for config file")); libs/program_options/src/config_file.cpp:60: boost::throw_exception(error("bad prefixes")); libs/program_options/src/value_semantic.cpp:102: boost::throw_exception(multiple_values()); libs/program_options/src/convert.cpp:66: boost::throw_exception(std::logic_error("character conversion failed")); libs/program_options/src/convert.cpp:74: boost::throw_exception(std::logic_error("character conversion failed")); libs/program_options/src/value_semantic.cpp:33: boost::throw_exception(std::runtime_error("UTF-8 conversion not supported.")); -- Dr. Leo Goodstadt University of Oxford United Kingdom

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[Serialization] Proposal for TR2
by Ruediger Berlich 15 Nov '11

15 Nov '11

Dear Robert, dear all. from what I understand, Boost.ASIO has been proposed for TR2 quite a while ago. Since I use ASIO and Boost.Serialization quite a bit and feel that both strongly benefit from each other (and not only ASIO -- see e.g. Boost.MPI), are there any efforts to make Boost.Serialization part of TR2 ? We live in the era of cloud computing and networked execution. Without this facility, C++ will have a hard time to compete. And Boost.Serialization is established and mature (thanks, Robert!). Best, Ruediger

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[context] ready
by Oliver Kowalke 14 Nov '11

14 Nov '11

Hi, https://github.com/olk/boost.context.git contains the new version of boost.context (docu at http://ok73.ok.funpic.de/boost/libs/context/doc/html/index.html) Any comments are welcome - in the meantime I'm awaiting Giovanni's OK for the mini-review. regards, Oliver

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Boost.Local Review (Nov 10, 2011 to Nov 19, 2011) by Krzysztof Czaiński
by Krzysztof Czainski 14 Nov '11

14 Nov '11

Hello, About me: I write C++ apps and RTS, mostly for embedded devices. I often use complicated C++ structures, and of course boost. Boost.Local caught my interest, so I decided to review it. I intend to try to use this library on MinGW-4.5, and on a Texas Instruments/DSP compiler, however I can't do that this week, so I won't make it until the end of this review. I studied the docs in depth. I state my comments below. Each of my comments is numbered in the style (0), so they can be referenced. https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost_loc… : Variable Binding: [quote] programmers might want to bind variables of complex types by (constant) reference instead than by value [/qoute] (1) s/instead than/instead of/ Binding the Object this: [quote] It is also possible to bind the object this when it is in scope (e.g., from an enclosing non-static member function). This is done by using this as the name of the variable to bind in the local function declaration and by using the special symbol this_ (instead of this) to access the object within the local function body. [/qoute] (2) Why not use this_ in both places? Local Blocks: (3) How is a Local Block better then just an ordinary C++ block: {}? So far, I have an idea of what such a Local Block is for, but a reference to a rationale at this point in the tutorial would be nice. Local Exits: [qoute]The execution of the local exit body code is guaranteed only if the program does not terminate because of an uncaught exception. [16] [/qoute] (4) To me this note requires more explanation. Consider three examples: (4a) [code] int main() { BOOST_LOCAL_EXIT( (void) ) { // Local exit. cout << "hello" << endl; } BOOST_LOCAL_EXIT_END throw 0; } // Local exit executed here. [/code] (4b) [code] int main() { try { BOOST_LOCAL_EXIT( (void) ) { // Local exit. cout << "hello" << endl; } BOOST_LOCAL_EXIT_END throw 0; } catch ( ... ) {} } // Local exit executed here. [/code] (4c) [code] int main() { try { throw 0; BOOST_LOCAL_EXIT( (void) ) { // Local exit. cout << "hello" << endl; } BOOST_LOCAL_EXIT_END } catch ( ... ) {} } // Local exit executed here. [/code] I which of the abouve examples is printing "hello" guaranteed? https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost_loc… : Assigning Local Functions: (5) In the example, variables named "l" (lowercase L) are used, which is easy to confuse with "1" (one), and therefore the example is hard to read. I suggest renaming that variable. Deducing Bound Types (concepts, etc): [qoute] it will also be a reference is the variable is bound by reference [/qoute] (6) typo: is -> if Inlining Local Functions [qoute]On C++03 compliant compilers, inlined local functions always have a run-time comparable to their equivalent implementation that uses local functors (see the Alternatives section). However, inlined local functions have the limitation that they cannot be assigned to other functors (like boost::function) and they cannot be passed as template parameters. [21] On C++11 compilers, inline has no effect because this library will automatically generate code that usesC++11 specific features to inline the local function calls whenever possible even if the local function is not declared inlined (unless the BOOST_LOCAL_CONFIG_COMPLIANT configuration macro is defined). Furthermore, non C++11local functions can always be passes as template parameters even when they are declared inlined.[/quote] (7) I read this paragraph four time, and still don't get it. Please rephrase is somehow ;-) (8) After reading the Introduction, Getting started, Tutorial and Advanced topics I still don't have an overview of the overhead, memory allocations, and exceptions that Local constructs can cause. Please add this information. Right now, I can deduce this information from the Implementation section. However, could things like lack of memory allocations or not emitting exceptions be promised in the public interface? https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_LOC… : Description: [qoute]As usual, exceptions specifications can be optionally programmed before the body code block (but the specifications will only apply the body code and not to the library code automatically generated by the macro expansion, see Advanced Topics). [/quote] (9)What are: the overhead, possible memory allocations, and exceptions, that Local constructs can cause? https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_LOC… : Description: [quote]If programmers leave this configuration macro undefined, its default value is to be left not defined.[/qoute] (10) What does it mean "its default value is to be left not defined"? Does it mean, that whether it's defined or not depends on the library, which tries to guess if the compiler supports variadic macros? [quote]If this macro is defined, variadic macros and empty macro parameters are not used by this library. Using variadic macros and empty macro parameters allows this library to provide the variadic macro and empty macro syntaxes which some programmers might find more readable than the sequencing macro syntax (see the Tutorial section, BOOST_LOCAL_FUNCTION_PARAMS, BOOST_LOCAL_BLOCK, and BOOST_LOCAL_EXIT). If this configuration macro is defined then only the sequencing macro syntax is allowed (regardless of whether the compiler supports variadic and empty macros or not).[/quote] (11)This paragraph is a bit unclear: first it says what happens if this macro is defined, then it says why variadic macros are useful, and lastly is says again what happens when this macro is defined. I suggest to make two paragraphs: first: state clearly what this macro does - disables the use of variadic macros, and second: comment on why variadic macros are useful. https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_LOC… : Description: [qoute]The execution of the local exit body code is guaranteed only if the program does not terminate because of an uncaught exception. As usual, exceptions specifications can be optionally programmed before the body code block (but the specifications will only apply the body code and not to the library code automatically generated by the macro expansion, see Advanced Topics).[/qoute] (12) Notes (4) and (9) apply here as well. https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_LOC… : Description: [qoute]As usual, exceptions specifications can be optionally programmed before the body code block (but the specifications will only apply the body code and not to the library code automatically generated by the macro expansion, see Advanced Topics).[/quote] (13) Note (9) applies here as well. https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_LOC… : Description: (14) What about the typename keyword inside templates? I think i remember from the previous sections, that typename is not required, but that information is missing here. https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_IDE… Description: [qoute]For example, if the expression type is know (and contains no commas)[/quote] (15) typo: know -> known This concludes my study of the docs, and I won't be able to try to use this library before the end of this review, so I state my conclusions now. 2011/11/10 Jeffrey Lee Hellrung, Jr. <jeffrey.hellrung(a)gmail.com> > Please state clearly whether you think this library should be accepted as a > Boost library. > Yes. Other questions you may want to consider: > > - What is your evaluation of the design? > I like it. > - What is your evaluation of the documentation? > I enjoyed reading it, and I think it gave me a pretty good idea about the library. > - What is your evaluation of the implementation? > >From what I read in the Implementation section of the docs, looks reasonable. > - What is your evaluation of the potential usefulness of the library? > I can imagine it would improve readability of some of my code. > - Did you try to use the library? With what compiler? Did you have any > problems? > No. I intend to, but not until the end of this review. > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? > In-depth study of the docs. > - Are you knowledgeable about the problem domain? > Hmm... I'll just say, I miss something like this for most of my 3-year experience of C++ programming. Please also consider the following issues and proposals specific to > Boost.Local. Your opinion is welcome on any or all of these. > > - Boost.Local's local exits provide the same functionality (and then some) > as Boost.ScopeExit. Does this duplication of functionality need to be > dealt with, and if so, how? I haven't used ScopeExit, so I don't have an opinion on this. - Lorenzo is proposing to add boost::local::function::overload to > Boost.Function as boost::function::overload. See > > https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost/loc… I don't remember missing such a utility in my experience, but it seems reasonable to add it to boost function. However, I don't understand, how can it be added as boost::function::overload, when boost::function is a class template? > - Lorenzo is proposing to add BOOST_IDENTITY_TYPE to boost/utility. See > > https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_IDE… > - Likewise, Lorenzo is proposing to add BOOST_IDENTITY_VALUE to > boost/utility. See > > https://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/BOOST_IDE… > I don't remember missing any of the above in my experience. One of "more readable alternatives" described in the docs have sufficed. Thanks in advance to all who participate in the review discussion; I'm > looking forward to it! > > - Jeffrey Hellrung (Review Manager) > - Gregory Crosswhite (Review Assistant) This was my first review, and I hope it's useful ;-) Regards, Kris

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Need for BOOST_PP_VARIADIC_POP_FRONT
by Gennadiy Rozental 14 Nov '11

14 Nov '11

Hi, I consider using Boost.PP variadic macros support, but I seems to be missing subject macro (with support for zero arguments). Any chance we can one? I'd hate to reinvent the wheel. Regards, Gennadiy

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