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

Fwd: [Thread] Solution to conflict with MFC?
by Thorsten Ottosen 28 Feb '13

28 Feb '13

Hi Thread maintainers, Anthony speaks about a patch to make this work. Does anyone know where it is? And could it be applied? Thanks -Thorsten -------- Original Meddelelse -------- Subject: [Thread] Solution to conflict with MFC? Date: Tue, 26 Apr 2011 13:28:56 +0200 From: Christian Larsen <contact(a)dword.dk> Reply-To: boost-users(a)lists.boost.org To: boost-users(a)lists.boost.org Newsgroups: gmane.comp.lib.boost.user Hello, I know this has been asked before, but I could not find a good solution. I'm experiencing problems with an application using both MFC and Boost.Thread. Specifically the assertion ASSERT(AfxGetModuleState() != AfxGetAppModuleState()); in AfxCoreInitModule() fails. I link Boost.Thread statically into a DLL in my project. From previous posts to this list and elsewhere, e.g. http://lists.boost.org/boost-users/2009/04/46929.php, I see that the issue is caused by setting _pRawDllMain in tss_pe.cpp. Commenting this line does "solve" the problem, but I would rather not have to hack the Boost source code this way. It seems there is a patch somewhere for this problem (referred to in http://lists.boost.org/boost-users/2009/04/47015.php) but it appears it never made it into the source. Is there any chance of this issue being solved in a better way? Best regards, Christian Larsen

5 9

[parameter] std proposal
by Lorenzo Caminiti 07 Jan '13

07 Jan '13

Hello all, Is there a C++ standard proposal for named parameter addition? I am looking for an "N-paper" for named parameters similar to N2081 for concepts, or N1962 for contracts. Thank you. -- Sent from my mobile device Lorenzo

6 8

[#pragma once]
by Sid Sacek 18 Nov '12

18 Nov '12

I've worked with the MSVC, Sun and GCC compilers. Each one of them supports #pragma once. Is there any reason to wrap this pragma within #ifdefs? Are there any compilers out there today that don't support this #pragma? #if defined( _MSC_VER ) && ( _MSC_VER >= 1020 ) # pragma once #endif Could we change this coding pattern so that it no longer looks like MSVC is being selfish? -Sid Sacek

17 20

[config] explicit call of operator templates / msvc bug workaround
by Stefan Strasser 10 Oct '12

10 Oct '12

Hi, is there already a macro in Boost.Config that allows you to insert the "template" keyword in the following code for those compilers that require it? struct functor{ template<class T> void operator()(); }; template<class F> void g(F f){ f.template operator()<int>(); //(1) works with GCC and comeau f.operator()<int>(); //(2) works with MSVC } this apparently only applies to operator calls. MSVC accepts both (1) and (2) for regular functions. (instantiating the operator template with an object of type T as argument, like mpl::for_each does, is not an option. I can't construct T.) thanks, Stefan

6 10

status of sp_counted_base_solaris.hpp
by Graham Bennett 07 Jun '12

07 Jun '12

Hi all, I'm interested in getting boost::shared_ptr to use atomic ops on Solaris. I notice there is an implementation using the OS-provided atomics in boost/detail/sp_counted_base_solaris.hpp, but it doesn't seem to be included. According to this thread: http://lists.boost.org/Archives/boost/2006/07/107144.php, it seems the reason might be that it wasn't possible to come up with a proper preprocessor condition to include it on the right versions of Solaris. I'm considering modifying my boost installation to include this header on Solaris - does anyone know of any issues with the code, or can they confirm that it has been well tested? Are there any other reasons for its omission? Thanks, Graham -- Graham Bennett

4 7

[contract] syntax redesign
by Lorenzo Caminiti 04 May '12

04 May '12

Hello all, After a long time of inactivity for Boost.Contract, I am considering how to re-design its macro syntax to make it simpler. I can eliminate a large number of extra parenthesis based on a few pp tricks I've learned in processing Boost.Local's `const bind(type)& var`. Plus, I can provide (optional) support for variadics macros so to use comma-separated pp tuplets instead of parenthesized pp sequences on preprocessors with variadics. For example, I _think_ (but I've not implemented this yet) that I can simplify the syntax like this: #include <contract.hpp> #include <vector> #include "myvector/pushable.hpp" // Wrapper class that adds contracts to std::vector. CONTRACT_CLASS( template( typename T ) class (myvector) extends( public pushable<T> ) // Subcontracting. ) { CONTRACT_CLASS_INVARIANT( empty() == (size() == 0) // More invariants here (comma separated)... ) CONTRACT_FUNCTION( public void (push_back)( (const T&) element ) precondition( size() < max_size() // More preconditions here (comma separated)... ) postcondition( auto old_size = CONTRACT_OLDOF(size()), // Old value. size() == old_size + 1 // More postconditions here (comma separated)... ) ) { vector_.push_back(element); // Implementation. } // Rest of the class here (with more contracts if needed)... public: typedef typename std::vector<T>::size_type size_type; size_type size(void) const { return vector_.size(); } size_type max_size(void) const { return vector_.max_size(); } bool empty(void) const { return vector_.empty(); } const T& back(void) const { return vector_.back(); } private: std::vector<T> vector_; }; For a side-by-side comparison with N1962 syntax: http://svn.boost.org/svn/boost/sandbox/contract/libs/contract/doc/html/inde… For a comparison of the entire std::vector (plus Boost.ConceptCheck concepts): http://svn.boost.org/svn/boost/sandbox/contract/libs/contract/doc/html/cont… For a comparison for all Boost.Contract features (plus Boost.ConceptCheck concepts and Boost.Parameter named parameters): http://svn.boost.org/svn/boost/sandbox/contract/libs/contract/doc/html/cont… (Don't pay attention to the rest of the docs that are way out of date.) A few notes: * Extra parenthesis are still needed around class and function names. * Extra parenthesis are still needed around types (like for the parameter `(T) element`) but only if the type is not a C++ keyword (no parenthesis needed aournd int, double, void, etc) or it contains a symbol (parenthesis needed if & or * are used `(int&) x`, etc). * In postconditions, the `auto old_size = CONTRACT_OLDOF(size())` only copies the vector size (and not the entire vector :)) ). Similarly, `auto result = return` can be used to access the return value for non-void functions. (The `auto ...` is parsed by the pp and it's implemented using Boost.Typeof so no C++0x is required.) * Template declaration (but not instantiation) angular parenthesis <> are replaced by round parenthesis (). All of this _should_ be implementable in pure ISO C++. What do you think? Based on the discontent that the previous "parenthesized" syntax generated among Boosters, the key question is: Would you consider this new syntax usable?? Thanks, --Lorenzo

5 45

[asio] Randomly having problems reading from the socket
by Torben Wiggerich 02 Apr '12

02 Apr '12

Hi all, I have some problems using the boost.asio.read for a TCP-socket. So far it works fine, but it randomly stops the transfer for at least 5 seconds. To resolve the error I used a simple synchronous server and client from the boost examples and modified it too send a larger amount of data. (307400 Bytes; this size comes from the program I'm trying to get run). On the client side I also changed the reading from the socket to read the complete data with boost.asio.read and transfer_all as argument. Both, server and client, measure the time for sending and reading to the socket and will give an error if it needs more than 1 second. Here is the sourcecode for the server: #include <iostream> #include <string> #include <boost/asio.hpp> #include <boost/date_time/posix_time/posix_time.hpp> using boost::asio::ip::tcp; using namespace boost::posix_time; int main() { try { boost::asio::io_service io_service; tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), 8002)); tcp::socket socket(io_service); acceptor.accept(socket); unsigned char * array = new unsigned char[307400]; for (;;) { boost::system::error_code ignored_error; ptime startTime = microsec_clock::universal_time(); boost::asio::write(socket, boost::asio::buffer( array, 307400 ), boost::asio::transfer_all(), ignored_error); time_duration neededTime = microsec_clock::universal_time() - startTime; if ( neededTime.total_milliseconds() > 1000 ) { std::cout << "ERROR needed too much time: " << neededTime.total_milliseconds() << "ms" << std::endl; } } } catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; } My client sourcecode: #include <iostream> #include <boost/array.hpp> #include <boost/asio.hpp> #include <boost/date_time/posix_time/posix_time.hpp> using boost::asio::ip::tcp; using namespace boost::posix_time; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: client <host>" << std::endl; return 1; } boost::asio::io_service io_service; boost::asio::ip::tcp::endpoint endpoint( boost::asio::ip::address::from_string( argv[1] ), 8002 ); tcp::socket socket(io_service); boost::system::error_code error = boost::asio::error::host_not_found; socket.connect( endpoint, error ); if (error) throw boost::system::system_error(error); int counter = 0; unsigned char* array = new unsigned char[307400]; for (;;) { boost::system::error_code error; ptime startTime = microsec_clock::universal_time(); size_t len = boost::asio::read( socket, boost::asio::buffer( array, 307400 ), boost::asio::transfer_all(), error ); time_duration neededTime = microsec_clock::universal_time() - startTime; if ( error ) { printf( "body read error %s\n", error.message().c_str() ); } if ( counter % 5000 == 0 ) { std::cout << "passed: " << counter << "\r"; } ++counter; if ( neededTime.total_milliseconds() > 1000 ) { std::cout << "ERROR needed too much time: " << neededTime.total_milliseconds() << "ms" << std::endl; } } } catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; } To reproduce the error just let it run for a while. It can take up to 30 minutes or even more... After a while it will produce the line: "ERROR needed too much time: 5007ms". Maybe with slightly different times, but all around 5 seconds. I tested it on different machines with Windows Vista and Seven. So am I'm doing sth. wrong? Is the reading from the socket correct? I'm using boost version 1.44. Kind regards Torben Wiggerich

6 11

[move] new rvalue reference emulation
by Jeffrey Lee Hellrung, Jr. 19 Feb '12

19 Feb '12

I've recently discovered (well, probably rediscovered) an alternate rvalue reference emulation, one which allows rvalues ***of any arbitrary (move-emulation-enabled) type*** to be captured in C++03 and identified as rvalues, rather than references-to-const (there is a drawback, though, which I'll get to below; as usual, there's no "free lunch"). This is in contrast to the current move emulation framework Ion has created in Boost.Move which, at best, allows you to capture rvalues of specific types. That is, if you can enumerate the types for which you want to enable rvalue capture, then you're good. For example, if you want to create a generic unary function some_fn, and you know you want to at least capture rvalues of type X, you could do: template< class T > void some_fn(T&); // captures (lvalue) references-to-non-const, explicitly created emulated rvalue references, *and* (lvalue) references-to-(X const) template< class T > typename boost::disable_if< boost::is_same<T,X> >::type void some_fn(T const &); // captures (lvalue) references-to-const *except* (lvalue) references-to-(X const) void some_fn(rv<X>&); // captures rvalues of X as emulated rvalue references However, if Y is any type other than X, the above overloads will capture an rvalue of Y as an (lvalue) reference-to-(Y const). This is one of the shortcomings of using the emulated rvalue reference rv<T>& as a function argument: it can't bind to rvalues in a context where the template parameter T is deduced. Now I don't know if the following proposition is a good idea or not, but I think it is worth considering. Again, we would like the emulated rvalue reference rv<T>& to bind to rvalues, but the problem is the deduction of the T template parameter. Instead of using rv<T>& to capture arbitrary rvalues, I'll use a kind of type-erased emulated rvalue reference, generic_rv<...> (for lack of a better name at the moment), which will just store a void pointer to the original, pre-type-erased object. Of course, we need some way to recover the object back from the void pointer, and that's what the "..." template parameters are for. This is where the (unfortunate) runtime overhead comes in, as some dispatching mechanism (e.g., function pointers) needs to be used to effect the recovery of the original, pre-type-erased object. The important difference between rv<T> and generic_rv<...> is that there's no T in the template parameter list "..." of generic_rv; more to the point, its template parameters are not deduced within the context of binding function arguments of some_fn, hence the compiler will be allowed to look for conversions from arbitrary rvalues to generic_rv<...>. Hopefully that gives enough of an introduction to the idea. Further details are probably best left to a code snippet. Comments? Specifically, should this be considered as an addition to Boost.Move's current emulation framework? Has anyone seen this technique before? ---------------- #include <iostream> #include <boost/type_traits/is_convertible.hpp> #include <boost/utility/enable_if.hpp> // rv<T>& emulates T&& template< class T > class rv : public T { rv(); rv(rv const &); rv& operator=(rv const &); }; template< class T > struct has_move_emulation : boost::is_convertible< T, rv<T>& > { }; // *** NEW EMULATED RVALUE REFERENCE *** // generic_rv< F, Result > also emulates an rvalue reference, but in a kind of // type-erased way. The actual object referred to is referenced by a void // pointer. To be able to cast the void pointer back to a pointer-to-object, we // need to package the void pointer together with some kind of dispatching // mechanism. We use a function pointer to an instantiation of cast_forward<T>. template< class F, class Result = void > struct generic_rv { typedef Result (*p_cast_forward_type)(F, void*); generic_rv(p_cast_forward_type p_cast_forward, void* p) : mp_cast_forward(p_cast_forward), m_p(p) { } Result cast_forward(F f) const { return (*mp_cast_forward)(f, m_p); } template< class T > static Result cast_forward(F f, void* const p) { return f(static_cast< rv<T>& >(*static_cast< T* >(p))); } private: p_cast_forward_type mp_cast_forward; void* m_p; }; // X is just a typical move-emulation-enabled class. struct X { X() { std::cout << "X::X()" << std::endl; } X(X const &) { std::cout << "X::X(X const &)" << std::endl; } X(rv<X>&) { std::cout << "X::X(rv<X>&)" << std::endl; } X& operator=(X) { std::cout << "X::operator=(X)" << std::endl; return *this; } X& operator=(rv<X>&) { std::cout << "X::operator=(rv<X>&)" << std::endl; return *this; } operator rv<X>&() { std::cout << "X::operator rv<X>&()" << std::endl; return *static_cast< rv<X>* >(this); } operator rv<X> const &() const { std::cout << "X::operator rv<X> const &() const" << std::endl; return *static_cast< rv<X> const * >(this); } // *** NEW CONVERSION OPERATOR *** // X provides an implicit conversion to generic_rv. template< class F, class Result > operator generic_rv< F, Result >() { std::cout << "X::operator generic_rv< F, Result >()" << std::endl; return generic_rv< F, Result >( &generic_rv< F, Result >::template cast_forward<X>, static_cast< void* >(this) ); } }; struct some_fn { template< class T > void operator()(T&) const { std::cout << "some_fn::operator()(T&) const" << std::endl; } template< class T > typename boost::disable_if< has_move_emulation<T> >::type operator()(T const &) const { std::cout << "some_fn::operator()(T const &) const" << std::endl; } // Notice that this overload requires template parameter deduction, hence // the compiler cannot apply an implicit conversion to rv<T>& from rvalues // of move-emulation-enabled types. In other words, this overload can only // bind to *explicitly* created emulated rvalue references, not to "real" // rvalues :( template< class T > void operator()(rv<T>&) const { std::cout << "some_fn::operator()(rv<T>&) const" << std::endl; } // *** NEW FUNCTION OVERLOAD TO CAPTURE RVALUES *** // Since this overload requires no template parameter deduction, the // compiler *can* apply an implicit conversion to generic_rv<...> from // rvalues of move-emulation-enabled types. Yes, there will be some runtime // overhead from the function pointer dispatching, but that will often be // preferable to copying x! void operator()(generic_rv< some_fn > const x) const { std::cout << "some_fn::operator()(generic_rv< some_fn >) const" << std::endl; return x.cast_forward(*this); } }; template< class T > T make() { return T(); } int main(int argc, char* argv[]) { int a = 0; int const b = 0; some_fn()(a); // some_fn::operator()(T&) const some_fn()(b); // some_fn::operator()(T const &) const some_fn()(make< int >()); // some_fn::operator()(T const &) const X x; // X::X() X const y; // X::X() some_fn()(x); // some_fn::operator()(T&) const some_fn()(y); // some_fn::operator()(T&) const some_fn()(make<X>()); // X::X() // X::operator generic_rv< F, Result >() // some_fn::operator()(generic_rv< some_fn >) const // some_fn::operator()(rv<T>&) const return 0; } ---------------- - Jeff

10 33

[preprocessor] Warning: Incoming
by Paul Mensonides 18 Jan '12

18 Jan '12

I'm about to commit a relatively significant changeset to the pp-lib. This is the result of work by Edward Diener and I to add limited variadic support to the pp-lib. Edward can comment in more detail regarding the extent of those changes, but they do not add ground-up support. However, there are significant changes to heavily used low-level facilities such as BOOST_PP_TUPLE_ELEM (sometimes even complete implementation replacements). We have put in a great deal of effort to avoid introducing new errors or warnings in either the building of the Boost binaries or in the regression tests. However, we may have missed some issues. Regards, Paul Mensonides

11 42

[mpl] integral_c [type_traits] integral_constant limits
by vicente.botet 04 Jan '12

04 Jan '12

Hi, I was testing Boost.Ratio with gcc-4.6 c++0x and I get some compile errors when instantiating std::cout << boost::mpl::integral_c< boost::intmax_t, boost::integer_traits<boost::intmax_t>::const_max >::value ; ..\..\..\../boost/mpl/aux_/integral_wrapper.hpp: In instantiation of 'mpl_::integral_c<long long int, 0x7fffffffffffffffll>': ratio_io\ratio_io.pass.cpp:24:6: instantiated from here ..\..\..\../boost/mpl/aux_/integral_wrapper.hpp:72:96: warning: integer overflow in expression [-Woverflow] ..\..\..\../boost/mpl/aux_/integral_wrapper.hpp:72:96: error: '-0x8000000000000000ll' is not a valid template argument for type 'long long int' because it is a non-constant expression ..\..\..\../boost/mpl/aux_/integral_wrapper.hpp:72:96: error: '-0x8000000000000000ll' is not a constant expression integral_wrapper.hpp:72 contains typedef AUX_WRAPPER_INST( BOOST_MPL_AUX_STATIC_CAST(AUX_WRAPPER_VALUE_TYPE, (value + 1)) ) next; The same line pass with gcc-4.6, gcc-4.5 and gcc-4.5 c++0x with just a warning. ..\..\..\../boost/mpl/aux_/integral_wrapper.hpp: In instantiation of 'mpl_::integral_c<long long int, 0x7fffffffffffffffll>': ratio_io\ratio_io.pass.cpp:23:6: instantiated from here ..\..\..\../boost/mpl/aux_/integral_wrapper.hpp:72:96: warning: integer overflow in expression [-Woverflow] integral_c is by integral_constant, but integral_constant doesn't needs next a prior types. This means that with the current implementation we can not use integral_constant with the max value of the type. Do you think this is a bug in integral_constant? Best, _____________________ Vicente Juan Botet Escribá http://viboes.blogspot.com/

4 6