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[OT][RFC] standardized compile-time reflection
by Matus Chochlik 27 Apr '12

27 Apr '12

Dear members of the Boost community, (Sorry for being slightly off-topic here) In the last couple or years I've been working on the design and implementation of portable reflection in C++. I've written several reflection libraries (that are hopefuly gradually improving). For the latest incarnation see the Mirror reflection utilities written in C++11: http://kifri.fri.uniza.sk/~chochlik/mirror-lib/html/ Recently I've learned that the Standardization Committee has issued a call for proposals for additions to the standard to the wider community, so I've decided to write down my own ideas on how compile-time reflection should look like in C++. Afterwards I discussed it with several people including Dean Michael Berris, who is the co-author of n3340 "Rich pointers" and is also interested in adding run-time (and static) reflection to C++. We've decided that we merge the ideas from my paper into his proposal (which has not happened yet and will probably take a while). However, n3340 deals with more than just static reflection, so I would like to start a discussion and ask the members of the Boost community for their opinions about the compile-time-specific parts that are described in the following paper, before writing the final proposal: http://kifri.fri.uniza.sk/~chochlik/jtc1_sc22_wg21/std_cpp_refl.pdf It is a bit lengthy so you can skip sections 1., 2. and probably also section 3., if you are knowledgeable about the domain. The most important parts are: the whole section 4. "Technical specification" and also 5., 6. and 7. Section 7. "Unresolved issues" lists several important things that need to be worked out and 3. has some rationale for the design decisions. Note that the paper has the basic structure of a standard proposal, but is not written in standardese nor is it "polished" (since it will be merged into another paper and probably re-worded). It is my first attempt at a standard proposal and I'm not a member of the Committee so please bear with me :-). Dean and I have also independently decided to write proof-of-concept implementations - compiler extensions for clang and gcc respectivelly. The sources for the gcc plugin are hosted here: https://github.com/matus-chochlik/std_cpp_refl It's in a very early stage, but if someone has some tips or hints they'll be welcome. Thanks in advance for any (negative or positive) feedback. Best regards, Matus Chochlik

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[assign] How to create a container wrapper for tuple_list_of
by Robert Dailey 26 Apr '12

26 Apr '12

I have a vector of boost::tuple objects that is a member variable in a class of mine. I want to be able to create an instance of my wrapper class and construct it off of a tuple_list_of(), and essentially forward those values to the container itself. I haven't seen a way to do this yet. An example is below. Note that my constructor in the class was my attempt to get this working, but instead it will not compile. For some reason boost.assign thinks that the EnumErrorInfo class is the container. template<class T> class EnumErrorInfo { public: typedef boost::tuple<T, char const*, char const*> Tuple; typedef std::vector<Tuple> TupleVector; EnumErrorInfo( TupleVector const& assignment ) : m_errorInfo( assignment ) {} Tuple const& getErrorInfo( T error_code ) { TupleVector::const_iterator it = std::find_if( m_errorInfo.begin(), m_errorInfo.end(), MatchErrorCodePred( error_code ) ); if( it != m_errorInfo.end() ) { return *it; } static Tuple const unknown_info( error_code, "????", "No error info available for this code" ); return unknown_info; } private: class MatchErrorCodePred { public: MatchErrorCodePred( T error_code ) : m_errorCode( error_code ) {} bool operator() ( Tuple const& t ) { return t.get<0>() == m_errorCode; } private: DomInterfaceErrors m_errorCode; }; TupleVector m_errorInfo; }; And here is how I'd like to initialize the class: EnumErrorInfo<DomInterfaceErrors> g_errorInfo = tuple_list_of ( GDE_OK, "GDE_OK", "DBL: Opeartion successfully completed" ) ( GDE_GDD_DIRUSERS, "GDE_GDD_DIRUSERS", "AQX: Unable to get directory users." ) ;

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[interprocess] Sharing shared_memory_object across processes?
by Joseph Van Riper 26 Apr '12

26 Apr '12

I either do not understand what I am seeing, or I may have stumbled upon a bug, at least in a Windows environment. Or, of course, my expectations may be unrealistic. The short of this is that when I create a boost::interprocess::shared_memory_object that isn't removed for the duration of the program's run, the reading program's run can't seem to open the shared_memory_object, despite creating a boost::interprocess::permissions object and calling 'set_unrestricted()'. I get an exception indicating that access is denied. If nothing else, the code I've provided is an interprocess version of the classic read-writer's problem, second version (writers preferred). It may be of use to someone with a little cleaning. Environment: Compiler: MSVC++ 10 OS: Win 7 Pro, 64-bit. Steps to reproduce: 1. In VC++ 10, create an empty command-line project. 2. Replace contents of your .cpp with the code in this e-mail. 3. Compile. 4. Run the executable twice, first with an argument, next without. Expected results: The executable run without arguments indicates how much data was transferred on the same line. Actual results: The executable run without arguments complains that access is denied. NOTE: If you #define BOLD_NEW_TEST and recompile, this program runs according to expectations. This causes the objects to be compiled in a way where the shared_memory_objects only last for as long as it takes to write or read the data. I suspect this shouldn't be necessary, but perhaps I'm wrong. The error is especially peculiar to me, as I can open the file itself with a text editor. It doesn't seem like it should be denied. - Trey

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[result_of] Make `cpp0x_result_of_impl` public
by Michel Morin 26 Apr '12

26 Apr '12

There are two implementations of boost::result_of: a TR1-style implementation and a decltype-based implementation. While the TR1-style implementation has a public interface `boost::tr1_result_of`, decltype-based one doesn't have a public interface. By defining BOOST_RESULT_OF_USE_DECLTYPE, boost::result_of use decltype-based implementation. But this is not always a viable solution, since this breaks some Boost libraries. So how about adding `boost::cxx11_result_of` as public interface of the decltype-based implementation? Attached a patch to add `boost::cxx11_result_of`. (This patch also changes the name of `cpp0x_result_of_impl` to `cxx11_result_of_impl` to reflect the recent discussion on the cpp/cxx naming.) P.S. Is it worth trying to use this `boost::cxx11_result_of` in `boost::transform_iterator` code on trunk? Regards, Michel

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[result_of] Regression: compilation errors on C++03 compilers when defining BOOST_RESULT_OF_USE_DECLTYPE
by Michel Morin 25 Apr '12

25 Apr '12

If we define BOOST_RESULT_OF_USE_DECLTYPE, boost::result_of tries to use decltype-based implementation even on C++03 compilers. This causes compilation errors and it is a regression on C++03 compilers. Is it intentional change? Regards, Michel

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[utility][assert]
by Yechezkel Mett 25 Apr '12

25 Apr '12

I noticed that when BOOST_ENABLE_ASSERT_HANDLER is defined, BOOST_ASSERT calls boost::assertion_failed whether or not NDEBUG is defined, but BOOST_ASSERT_MSG calls boost::assertion_failed_msg only if NDEBUG is not defined. Is there a reason for this difference?

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[exception] applying patch for issue #6349
by David Deakins 24 Apr '12

24 Apr '12

Hi Emil, Since the issue in item #6349 is disrupting the Windows CE test results for many libraries, do you mind if I go ahead and apply the patch attached to that item? Thanks, -Dave

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[Iterator] Fixing the default reference type of transform_iterator (#5127)
by Michel Morin 24 Apr '12

24 Apr '12

The default reference type of transform_iterator should be boost::result_of<const UnaryFunction(Iterator::reference)> rather than boost::result_of<UnaryFunction(Iterator::reference)> since the dereference operator of transform_iterator is a const member function. Ticket #5127 describes this bug https://svn.boost.org/trac/boost/ticket/5127 and the ticket has a patch. Jeff, could you apply the patch, if it looks OK? Regards, Michel

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[contract] assertion requirements as meta-functions or not?
by lcaminiti 24 Apr '12

24 Apr '12

Hello all, Boost.Contract allows to specify "assertion requirements": /assertion-condition/, requires /assertion-requirement/ If the requirement is not met then the assertion condition is neither compiled nor checked at run-time. Question: Shall the assertion-requirement be a nullary boolean meta-function or just a static boolean value? For example: CONTRACT_FUNCTION( template( typename T ) requires( boost::LessThanComparable<T> ) (T const&) (min) ( (T const&) x, (T const&) y ) postcondition( auto result = return, x < y ? result == x : result == y, requires boost::has_equal_to<T>::value // static boolean ) ) { return x < y ? x : y; // OK: T is less than comparable `<`. } For now, the assertion requirement is a static boolean value so it can be more easily manipulated (using !, &&, ||, etc instead of mpl::not, mpl::and, mpl::or, etc). However, is there any strong reason for marking the assertion requirement a nullary boolean meta-function instead like the following code? x < y ? result == x : result == y, requires boost::has_equal_to<T> // meta-function Thanks. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-contract-assertion-requirements-as… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[Fusion] Patch: fixing some test failures on clang
by Michel Morin 24 Apr '12

24 Apr '12

The following tests of Boost.Fusion fail on clang trunk in a C++11 mode with libc++. * io.test * deque_construction.test * deque_misc.test * std_tuple_iterator.test * invoke.test Attached a patch for fixing two failures (io.test and std_tuple_iterator.test) of them. Regards, Michel

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