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Any interest in dynamic dispatching mechanism from "interface" to template functions ?
by Raffi Enficiaud 16 Sep '10

16 Sep '10

Hello all, The idea behind is not new and consists in dispatching a call of an interface function to the correct template instance, depending on the runtime or compile time parameters. The field of application is (to me) the release of static/dynamic libraries including functions with a predefined set of types combination. This way, the library (compiled once) can easily be plugged to another framework or a script program (I personally use it with boost.python). An example of use could be (general idea, not a real code of course): // -------------- template <class real_type> int template_function(real_type const& r_class1, double param_d, int& param_out) { // ... return 0; } int interface_function(MyInterface const* i_class1, variant const& param, variant& out) { // return value int return_value; // constructs the dispatcher object with a reference to the values passed to interface_function dispatcher<int, MyInterface const*, variant const&, variant&> dispatch_object(return_value, i_class1, param, out); bool res = dispatch_object.calls_first( fusion::vector_tie( template_function < class_t1 >, template_function < class_t2 > //... ) ); if(res) return return_value; return -1; } // -------------- The dispatch_object tests for the convertibility of each instance ui of the arguments Ui of the interface function, with the corresponding argument Ti of the template function. The type of matching is defined by external objects, with a simple interface providing two methods: a convertibility test and a conversion. The types are "cleaned" in order to have a limited number of conversion structures. Currently this mechanism is used in a generic image processing library. The images have all the same virtual interface and the dispatch calls the correct template function based on the concrete type of the image. It also includes a "back conversion" for Ui's that are non-const reference or pointers. The dispatch mainly makes use of boost.fusion, boost.mpl and boost.function_types. I have checked a little bit the Boost.Vault but, correct me if I am wrong, the current dispatching mechanisms do not address exactly this issue. The code is already open-source released under the boost license. I can put some samples in the Vault if there is any interest. Your comments are very welcome ! Kind regards, Raffi Enficiaud

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[serialization] Must the objects being serialized outlive the archive?
by Chris Yuen 15 Sep '10

15 Sep '10

Hi, I am using boost::serialization along with the eos::portable_archive (on Boost Vault). All the data that I serialize are polymorphic types, i.e. pointers. By experiment and days of frustration, I found out that the objects being serialized must "outlive" the archive or the serialization process -- otherwise I'd get segfault and corrupt data. I hope that was clear. To demonstrate this, I wrote a small example at http://boost.codepad.org/mqX5dUf6 (I'm a noob and I don't know the tradition to paste code -- should I just paste it in the message body or something?) The program will crash when you run it. However, if you comment out both the "delete" statements (leading to memory leaks, but at least the objects will outlive the archives), then everything works fine. Is there a way so that I can "flush" the serialization process so that it gets written immediately? The way that it is now, I must keep in memory all the things that I want to serialize. Thanks! Chris Yuen

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[thread] tss_null.cpp missing namespace boost
by David Deakins 14 Sep '10

14 Sep '10

When the changes were made a few months ago to move all the tss hook functions from the global namespace to the boost namespace, it looks like tss_null.cpp got left out. It's tss_cleanup_implemented stub function (used for the regression tests) is still over in the global namespace. I opened up ticket 4650 with a patch that fixes this issue. Let me know if there are questions, -Dave

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Boost container similar to Judy arrays?
by Achilleas Margaritis 14 Sep '10

14 Sep '10

Hi all. Does boost have a container with similar properties to Judy arrays? I searched the documentation but I did not find anything similar. Here is the Judy arrays home page: http://judy.sourceforge.net/index.html __________ Information from ESET Smart Security, version of virus signature database 4486 (20091007) __________ The message was checked by ESET Smart Security. http://www.eset.com __________ Information from ESET Smart Security, version of virus signature database 4486 (20091007) __________ The message was checked by ESET Smart Security. http://www.eset.com

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Re: [boost] Scalpel: a Spirit&Wave-powered C++ source code analysis library
by Brian Wood 14 Sep '10

14 Sep '10

Doug Gregor: >I want to see great, new ideas in C++ parsing and development tools, >but I strongly feel that those ideas could be far better disseminated >through extending/adapting/changing existing the large-scale, >industry-backed projects (GCC or Clang/LLVM) than by bringing up a >third large-scale competitor. Years ago I looked at GCC and considered using it as a basis for what I'm working on, but after spending a few months working with the code, concluded it wouldn't make a good basis for my project. Perhaps you are being generous about it here, but I can't recommend anyone join that project. I certainly hope Clang is superior to GCC in many ways. -- Brian Wood Ebenezer Enterprises http://webEbenezer.net (651) 251-9384 "If you can't join 'em, beat em."

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Link error in Boost Exception MSVC tests
by Emil Dotchevski 13 Sep '10

13 Sep '10

Does anyone have an idea why I'm getting this error: http://tinyurl.com/392vnmk (this works when I run the tests on my own system.) Thanks, Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode

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application for the "Who's Using Boost?" list
by Roni Simonian 13 Sep '10

13 Sep '10

# The name of the product: Maze (TM) # The name of the company: Ariadne LLC # A paragraph describing the product: Maze (TM) is a professional tool for parallel programming. It provides a deterministic environment for testing and debugging multiprocess and multithreaded applications on X86 and X86-64 Linux platforms. # Parts of Boost you used: Bind, Enable_If, Exception, Filesystem, Function, StaticAssert, TypeTraits, Utility # URL: www.ariadne-soft.com

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[Proto][Phoenix] Use default transform with SFINAE for expressions?
by Mathias Gaunard 13 Sep '10

13 Sep '10

I would quite like it if polymorphic function objects created by Phoenix could restrict overload resolution to types for which their function body is valid, using SFINAE for expressions. Basically, this would allow something like this: struct foo {}; void dummy_function(...) { std::cout << "[not streamable]"; } make_overload( std::cout << arg1, dummy_function ) (foo()); (with make_overload what you'd expect) The dummy function would be called if the first one doesn't match, instead of resulting in a hard error. (surely it would also be nice to add a module to create "..." functions in Phoenix, but that should be easy) Now I looked a bit at how Phoenix v3 and Proto work, and it seems the main problem to do that is in the default transform. Albeit it uses decltype for its return type, this is not done in a template deduction context, which prevents it from doing its SFINAE magic. I tried to do that, but then a transform is assumed everywhere to be monomorphic, so SFINAE doesn't "propagate" out of default_TAG. Before I go ahead and try to convert all result_type to result with templates, which could affect compile-time, I'd like to have some feedback on the whole idea, and whether this is the right way to do it.

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[Locale] Preview of 3rd version
by Artyom 13 Sep '10

13 Sep '10

Hello All, Announcement ============ I want to announce a preview of the third version of Boost.Locale: Tutorial: http://cppcms.sourceforge.net/boost_locale/html/tutorial.html Reference: http://cppcms.sourceforge.net/boost_locale/html/index.html Downloads: https://sourceforge.net/projects/cppcms/files/boost_locale/ There are following significant changes: - Implemented multiple localization backends: - icu - the default and recommended backend, based on ICU library - std - based on C++ standard library localizations support, - posix - based on POSIX 2008 API (newlocale, strftime_l,...) - winapi - based on Windows API functions - Significantly simplified locale generation. - Improvements in UTF-8 handling by ICU where possible - Thread safety fixes when using ICU library - Fixed std::codecvt facet support to handle UTF-16 instead of UCS-2 only. - Removed support of compilers missing wide character support, gcc-3.4 on windows is not supported any more, latest gcc-4.x required with support of wide streams and strings, for example gcc-4.5 Tested Platforms: - Compilers: GCC (3.4, 4.2, 4.3, 4.5, 4.5/c++0x), Intel 11.0, MSVC 2008, SunStudio/stlport - Operating Systems: Linux, FreeBSD, OpenSolaris, Windows XP, Cygwin 1.7, (TODO Mac OS X) - ICU version: 3.6 to 4.4 Request To Site managers ========================= Please, update download link Review ====== Is there anybody who wants to volunteer to be a review manager? Artyom

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[local_function] passing local functions as template parameters
by Lorenzo Caminiti 13 Sep '10

13 Sep '10

Hello all, Can you please check if the following mechanism can be used to pass local functor classes as template parameters? PROBLEM If I understand the C++ standard right, local classes cannot be passed as template parameters. Because of that, if I am defining a functor to pass to `std::for_each` I have to define it outside the local scope, far from the `for_each` call, which is not ideal (from cplusplus.com) struct myclass { void operator() (int i) {cout << " " << i;} } myobject; int main () { // Ideally `myclass` would be defined here locally... vector<int> myvector; myvector.push_back(10); myvector.push_back(20); myvector.push_back(30); cout << "\nmyvector contains:"; for_each (myvector.begin(), myvector.end(), myobject); cout << endl; return 0; } The code above does not compile on GCC if `myclass` is defined locally within `main`'s scope (it still compiles on MSVC instead...). SOLUTION (?) The following mechanism allows to define the functor body locally (in a local function which also binds the in-scope parameter `x`) and then pass it as a template parameter (to `boost::bind()` and then to `std::for_each()`). The trick is for the local function to override the virtual body of a global class and then pass the local function as a pointer to the global class while dynamic binding will actually execute the locally overridden body code. #include <boost/function.hpp> #include <boost/bind.hpp> #include <iostream> #include <algorithm> #include <vector> template<typename F> struct lfn_global {}; template<typename A1> struct lfn_global<void (A1)> { virtual void body(A1) {} }; // Similarly define `lfn_global` for other function arities and return types. int main () { double x = 5.6; struct lfn_t: lfn_global<void (int)> { lfn_t(double const& bound_x): x(bound_x) {} void body(int i) { std::cout << " " << i + x; // Local func body. } private: double const& x; } lfn_obj(x); // x is const& bound from scope. boost::function<void (int)> lfn = boost::bind( &lfn_global<void (int)>::body, (lfn_global<void (int)>*)(&lfn_obj), _1); std::vector<int> v; v.push_back(10); v.push_back(20); v.push_back(30); std::cout << "v: "; std::for_each(v.begin(), v.end(), lfn); // I can pass the local functor! std::cout << std::endl; return 0; } This code compiles on both GCC and MSVC, it correctly prints "v: 15.6 25.6 35.6". If this indeed works, I can hide all the extra code it requires behind the `BOOST_LOCAL_FUNCTION...` macros. Can you please try this code on other compilers? Do you see any issue with this code? Thank you very much. -- Lorenzo

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