September 2012 - Boost - lists.boost.org

Proposed new RAII Library
by Andrew Sandoval 17 Sep '12

17 Sep '12

I'd like to propose a new Boost library for RAII wrapper classes that I think could be standardized to help promote the use of RAII. Though shared_ptr, scoped_ptr, etc. greatly enhance the use of RAII, I propose two additional classes. The first of these is RAIIFunction (I'm open to other names and coding conventions). This one is very simple, but powerful. It's a small wrapper (using composition) around std::tr1::function, that simply calls the function on scope-exit, in the normal case. Unlike Boost.ScopeExit, it uses no macros. Anything that can be assigned to a std::tr1::function<AnyType> taking no parameters will work with it, so lambdas are perfect -- and allow for all of the associated benefits like capturing variables by reference, etc. It also works with std::tr1::bind / boost::bind, with no placeholders. // // RAIIFunction<> Written by Andrew L. Sandoval 2011/2012 // Include guard here #include <functional> // // An RAII class that works with std::tr1::bind and lambdas // NOTE: making a const RAIIFunction prevents the use of Invoke() // and Cancel() and operator=(fn) which is often appropriate // NOTE: m_func copies the original function object, so that const and // non-const refs can be passed in, etc. template <typename TRet> class RAIIFunction { private: std::tr1::function<TRet ()> m_func; bool m_bInvoke; RAIIFunction(); RAIIFunction(const RAIIFunction &); void operator=(const RAIIFunction &); public: RAIIFunction(const std::tr1::function<TRet ()> &fn) : m_func(fn), m_bInvoke(true) { } void operator=(const std::tr1::function<TRet ()> &fn) { if(m_bInvoke) { m_func(); } m_bInvoke = true; m_func = fn; } ~RAIIFunction() { if(m_bInvoke) { m_func(); } } void Cancel() { m_bInvoke = false; } TRet Invoke(bool bRelease = false) { m_bInvoke = !bRelease; return m_func(); } }; Examples: const RAIIFunction<void> closeDB = ([pDB]() { if(pDB) { sqlite3_close(pDB); } }); // // while example... bool bContinue = true; RECORD record = { }; while(bContinue) { // Ensure that no matter how the loop wraps (continue or fall-through) the next // record is grabbed or the loop terminates... const RAIIFunction<void> loopAdvance = ([&bContinue]() { bContinue = SomeCallThatGetsAnotherRecord(record); }); // A bunch of record processing here ... } // // A convoluted example that shows assignment, etc. RAIIFunction<int> mb = std::tr1::bind(MessageBoxW, HWND_TOP, L"Present pop-up prompt again?", L"Test", MB_TOPMOST|MB_YESNO); int iMB = mb.Invoke(true); if(IDYES != iMB) { mb = ([]() ->int { dprintf("Printing what the user didn't wanted popped up" " on scope-exit...\n"); return 0; }); -- The other one I call just RAIIWrapper, and it works with static deleter functions taking a single argument of the type being delete. Since it includes a lot more code (much of which could probably be replaced with type_traits code), I'll just show examples of usage below to gauge interest. I first used an earlier version of this in an environment where the standard function required a goto ErrorExit (like Microsoft example driver code in the WDK) to clean-up all of the resources. The original concern was that the c++ class would bloat the deliverable size. This class proved to be as tight as the goto equivalent. It uses one macro that I'll include below. The class takes 3 template parameters: 1) The type of the deleter function, 2) the deleter function, and 3) a no-delete value that defaults to NULL. // // Simplify usage with a macro: #define RAIIDeleter(deleterFunction) decltype(&deleterFunction), deleterFunction // Example: const RAIIWrapper<RAIIDeleter(CloseHandle), INVALID_HANDLE_VALUE> hFile = CreateFile(pwzFileName, GENERIC_WRITE, FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL); if(!hFile.IsValid()) { // handle error... } // Similar but using the default no-delete value (NULL): const RAIIWrapper<RAIIDeleter(CloseHandle)> hEvent = CreateEvent(NULL, FALSE, FALSE, NULL); -- I've found that using RAII consistently can dramatically improve code quality. It forces the coder to think about resource lifetime at inception rather than at exit points, etc. Much of what I've shown above can be done with scoped_ptr or shared_ptr, but these specialized classes put the focus on RAII and resource management. Please let me know your thoughts. I'd love to see this become part of Boost, and hopefully eventually part of the C++ standard library. Thank You, Andrew Sandoval

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[rational] optional over/underflow checking
by Dan Searles 17 Sep '12

17 Sep '12

>> https://svn.boost.org/svn/boost/sandbox/rational Sandbox now includes the test driver. All the updates are in the single rational header file, so this is a relatively small update. Rational.h, however, has had small updates before. This update centers on adding an optional over/underflow check, that would generate an exception if the result of an operation could not be represented with full numeric precision. Seeking comments on the update and any steps/requirements needed to get the update accepted for release. BTW, are there any status updates on the unlimited precision numeric class effort? Thanks, Dan Searles

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Re: [boost] [result_of] Usage guidelines
by Andrey Semashev 17 Sep '12

17 Sep '12

Ok, here is my second take on this. I've attached a patch with my changes. 1. I moved the guidelines to a separate section in order not to clutter the formal result_of description. 2. I seperately outlined the C++11 and C++03 recommendations. 3. I left the result_of examples. I think they illustrate the result_of usage quite well, but I'll be happy if someone comes up with something better. 4. I rephrased some of the wording about result<> usage, in response to Jeffrey's reply. Comments are welcome.

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[ASIO] async SSL operations unnecessary serialized?
by Michał Madziar 16 Sep '12

16 Sep '12

Hello all. It looks like all openssl_operation handlers are synchronized on io_service allowing only one connection to be processed at the a time. As I understand this orginated from the time when libopenSSL didn't support multi-threaded applications, but it slows down everything a lot. Adding locking function, and getting rid of strand_->wrap in lines 320, 385 in file boost/asio/ssl/detail/openssl_operation.hpp allows SSL connections to be used in multiple threads simultaneously solving the problem. Or do I miss something? I've attached simple line-based echo server which demonstrates the problem: openssl s_client -connect localhost:10001 #x 2 telnet localhost 10000 #x 2 After sending something in each connection TCP and one SSL work in parallel, second SSL waits with receiving until first one finishes it's write. After patching all connections work in parallel. -- Pozdrawiam Michał 'michoo' Madziar

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{Review] Coroutine reviewstarts today, September 3rd
by Hartmut Kaiser 16 Sep '12

16 Sep '12

Hi all, The review of Oliver Kowalke's Boost.Coroutine library starts today, September 3rd 2012, and will end on September 12th. I really hope to see your vote and your participation in the discussions on the Boost mailing lists! ----------------------------------------------------- About the library: Boost.Coroutine provides templates for generalized subroutines (coroutines) which allow multiple entry points for suspending and resuming execution at certain locations. It preserves local state/data and allows re-entering subroutines more than once (useful if state must be kept across function calls). Coroutines can be viewed as a language-level construct providing a special kind of control flow. You can download the library and the view documentation here: docs: http://ok73.ok.funpic.de/boost/libs/coroutine/doc/html/ src: http://ok73.ok.funpic.de/boost.coroutine.zip --------------------------------------------------- Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - 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? Regards Hartmut Review Manager

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[result_of] Make result_of doc separate from utility.htm
by Michel Morin 16 Sep '12

16 Sep '12

The documentation of result_of is contained in monolithic utility documentation: http://www.boost.org/libs/utility/utility.htm But I think result_of is worth having its own (i.e. separate) documentation. Comments? Regards, Michel

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[ublas] Trunk testing broken
by Belcourt, Kenneth 15 Sep '12

15 Sep '12

Someone forgot to commit a file? error: Unable to find file or target named error: 'test_ticket7296.cpp' error: referred to from project at error: '../libs/numeric/ublas/test'

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[nowide] Library looks for a review manager
by Artyom Beilis 15 Sep '12

15 Sep '12

Hello, The project Boost.Nowide searches a review manager: What is Boost.Nowide: --------------------- Boost.Nowide is a library implemented by Artyom Beilis that make cross platform Unicode aware programming easier. The library provides an implementation of standard C and C++ library functions, such that their inputs are UTF-8 aware on Windows without requiring to use Wide API. Documentation: http://cppcms.com/files/nowide/html/ Downloads: http://cppcms.com/files/nowide/ Artyom Beilis -------------- CppCMS - C++ Web Framework: http://cppcms.com/ CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/

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[system] Patches to apply when BOOST_ERROR_CODE_HEADER_ONLY or BOOST_NO_EXCEPTIONS are defined
by Vicente J. Botet Escriba 15 Sep '12

15 Sep '12

Hi, I have added some simple patches for these two tickets https://svn.boost.org/trac/boost/ticket/7347:duplicate symbol while BOOST_ERROR_CODE_HEADER_ONLY is defined https://svn.boost.org/trac/boost/ticket/7149:system failed to compile with BOOST_NO_EXCEPTIONS defined when -fno-exceptions is NOT used Could I apply them to trunk? Best, Vicente

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[system] Patches to apply when BOOST_ERROR_CODE_HEADER_ONLY or BOOST_NO_EXCEPTIONS are defined
by Vicente J. Botet Escriba 15 Sep '12

15 Sep '12

Hi, I have added some simple patches for these two tickets https://svn.boost.org/trac/boost/ticket/7347:duplicate symbol while BOOST_ERROR_CODE_HEADER_ONLY is defined https://svn.boost.org/trac/boost/ticket/7149:system failed to compile with BOOST_NO_EXCEPTIONS defined when -fno-exceptions is NOT used Could I apply them to trunk? Best, Vicente

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