- Boost-users - lists.boost.org

Re: [Boost-users] UPDATE rules
by spamjunk 21 Feb '11

21 Feb '11

Sure, why worry about backwards compatibility. When is that ever important? Guess I'll stick with .17.

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Re: [Boost-users] UPDATE rules
by spamjunk 21 Feb '11

21 Feb '11

> I thought that's how Boost.Build always worked. That *may* be how Boost.Build works. I don't know. I don't use it. I only use BJAM. Version 3.1.18 added these lines to jam.c: if (!targets_to_update()) mark_target_for_updating("all"); Thus, if no target is defined on the command line, it force it to "all." These lines do not exist in 3.1.17.

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Re: [Boost-users] Determine at compile time whether type has subtraction semantics?
by Raymond Burkholder 21 Feb '11

21 Feb '11

> On 19/02/11 06:51, Frédéric Bron wrote: > >> Is it possible to determine at compile-time if a type has subtraction > >> semantics? E.g. in struct A<T> I would like to decide at compile-time not > to > >> execute&A::subtract in the register_fns method. Then the subtract > method is > >> not instantiated and there is no error. > Is there any way to do use the type traits to conditionally compile some > code using some brief syntax? I.e. it would be nice if something like > the following worked: > I think you are looking for something along the lines of what is suggested "An Optimized Version of std::copy" in the type_traits examples. http://www.boost.org/doc/libs/1_45_0/libs/type_traits/doc/html/boost_typetra its/examples/copy.html It provides conditional compilation via a form of template indirection/selection. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.

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Determine at compile time whether type has subtraction semantics?
by John Reid 21 Feb '11

21 Feb '11

Is it possible to determine at compile-time if a type has subtraction semantics? E.g. in struct A<T> I would like to decide at compile-time not to execute &A::subtract in the register_fns method. Then the subtract method is not instantiated and there is no error. template< typename T > struct A { void register_fns() { &A::subtract; } T subtract( T x, T y ) { return x - y; } }; void test() { A< int >().register_fns(); // int: Fine A< std::string >().register_fns(); // string: Compile error } I didn't see anything in Boost.TypeTraits Thanks, John.

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UPDATE rules
by spamjunk 21 Feb '11

21 Feb '11

Is seems that the UPDATE rule for BJAM was changed for 3.1.18. Now, if no targets are defined on the command line, UPDATE defaults to "all". See line #452 of jam.c. This is annoying. I don't want my default to be all, but there is no way (that I know of) the distinguish between an explicit "all" on the command line, and the new defaulted, implicit one. Anyone know of a workaround (outside of changing the code or using an older version)? Thanks.

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[ICL] lower(interval_set) doesn't compile
by John Reid 21 Feb '11

21 Feb '11

I'm not sure if I'm getting the wrong end of the stick from the docs or perhaps I should raise this sort of thing as a bug report? #include <boost/icl/interval_set.hpp> namespace icl = ::boost::icl; void interval_set_intersects() { icl::lower( icl::interval_set< int >() ); } gives: In file included from /home/john/Dev/ThirdParty/boost/boost-trunk/boost/icl/associative_interval_container.hpp:16, from /home/john/Dev/ThirdParty/boost/boost-trunk/boost/icl/interval_base_set.hpp:24, from /home/john/Dev/ThirdParty/boost/boost-trunk/boost/icl/interval_set.hpp:14, from src/sandbox.cpp:2: /home/john/Dev/ThirdParty/boost/boost-trunk/boost/icl/concept/interval_associator.hpp: In function ‘boost::enable_if< boost::icl::is_interval_container<boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator> >, boost::icl::interval_set< int, less, boost::icl::discrete_interval<int, less>, allocator>::interval_type >::type boost::icl::lower(const boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator> &)’: src/sandbox.cpp:6: instantiated from here /home/john/Dev/ThirdParty/boost/boost-trunk/boost/icl/concept/interval_associator.hpp:229: error: no match for ternary ‘operator?:’ in ‘boost::icl::is_empty( ( (const boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator> &)( (const boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator> *)object))) ? boost::icl::identity_element< boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator> >::value() : boost::icl::lower( ( (const boost::icl::discrete_interval<int, less> &)( ( const boost::icl::discrete_interval<int, less> * )boost::icl::key_value( ( (const boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator> *)object )->boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator>::< anonymous >.boost::icl::interval_base_set< boost::icl::interval_set<int, less, boost::icl::discrete_interval<int, less>, allocator>, int, less, boost::icl::discrete_interval<int, less>, allocator>::begin()))))’ using boost SVN version 68955 and gcc 4.4.3

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[boost.signals2] queries
by Sean Farrow 21 Feb '11

21 Feb '11

Hi: I am looking in to using boost.signals2 for a project I'm involved in, but have a few queries: Firstly, if I create a global signall: boost::signals2::signal<void ()> sig; and then a structure: struct DoWork { void operator()() const { //work. } If I then create a private member of a class: DoWork work; And then do: Sig.connect(Work); Will the connection happen on the thread in which the work member variable was defined or will a second thread be utilized? Also given that sig will be a global and hence accessed from multiple threads, do I need a mutex? Cheers Sean.

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Timing out when writing to serial port while still receiving data
by Goetz, Russ 21 Feb '11

21 Feb '11

I've created a wrapper class around boost asio's serial_port class: class SerialPort { public: void open(); void send(const std::vector<uint8> &data); void close(); private: void _startReceiving(); boost::asio::serial_port m_serialPort; boost::asio::io_service m_ioService; std::vector<uint8> m_recvBuf; }; The SerialPort class has an 'open' member function that opens the port and begins waiting for data to be received on the serial port. There's also a 'send' member function that writes the specified data to the serial port. Below is the code (running on a separate thread) that waits for data to be received on the serial port: Receive Thread -------------- while (m_recvData) { m_serialPort.async_read_some(boost::asio::buffer(m_recvBuf), boost::bind(&SerialPort::_recvHandler, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); m_ioService.run(); m_ioService.reset(); } The problem I'm experiencing is that when the flow control of the serial port is set to RTS/CTS, and I try and write to the serial port with the cable unplugged or the CTS serial line otherwise low, the call is a blocking call. I realize this is the way it's supposed to work, but I need to make writing to the serial port timeout after a few hundred milliseconds instead of blocking until CTS goes high. So I found code on the boost user's mailing list to do just that (m_writeDoneEvent is a manual reset event): Write Thread ------------ boost::optional<boost::system::error_code> timerResult; boost::asio::deadline_timer writeTimer(m_ioService); writeTimer.expires_from_now(milliseconds(100)); writeTimer.async_wait(boost::bind(&SerialPort::_writeDone, this, &timerResult, (std::size_t*)NULLPTR, _1, 0)); boost::optional<boost::system::error_code> writeResult; std::size_t bytesWritten; boost::asio::async_write(m_serialPort, boost::asio::buffer(data, length), boost::bind(&SerialPort::_writeDone, this, &writeResult, &bytesWritten, _1, _2)); // Wait for the write to finish, either due to success or timing out. m_writeDoneEvent.wait(); m_writeDoneEvent.unset(); if (writeResult) { // Write completed successfully. writeTimer.cancel(); if (writeResult->value()) { std::ostringstream oss; oss << "Failed to send some or all of the data to " << m_portName << ". Successfully sent " << bytesWritten << " of a possible " << length << " bytes."; throw SerialException(oss.str(), writeResult->value()); } } else if (timerResult) { // Write timed out. Cancel all asynchronous operations (including the // asynchronous call to read). m_serialPort.cancel(); // <==== ***Throws exception*** std::ostringstream oss; oss << "Sending to " << m_portName << " timed out."; throw SerialException(oss.str()); } void SerialPort::_writeDone(boost::optional<boost::system::error_code> *errorToSet, std::size_t *bytesWrittenToSet, const boost::system::error_code &error, std::size_t bytesWritten) const { if (error != boost::asio::error::operation_aborted) { // Set the error code so the caller knows why the asynchronous write //operation finished. errorToSet->reset(error); if (bytesWrittenToSet != NULLPTR) { *bytesWrittenToSet = bytesWritten; } // Signal to the caller that the write operation is complete. m_writeDoneEvent.set(); } } However, when the write operation on the serial port times out, the call to m_serialPort.cancel() above throws an exception, saying 'The attempted operation is not supported for the type of object referenced'. Looking at the source code, the comment where the exception is thrown says that it's an unsafe operation to call cancel on the IO service from a thread when work has been given to the IO service from a different thread. This obviously fits my case - I've submitted an async_read on the Receive thread and I'm trying to cancel all asynchronous work on the Write thread. Is it possible to have a thread always running that's waiting for data to be received on the serial port as well as have a write thread that timeouts? If so, where did I go wrong above? Thanks, Russ

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[boost.asio] issues with io_service.run
by Sean Farrow 21 Feb '11

21 Feb '11

Hi: Ok, I'm trying to use boost::asio::io_service::run as follows. At the top of a .hpp file I have: typedef boost::asio::io_service FolderMonitoringService; I can pass this to a constructor requiring an io_service as follows: boost::asio::dir_monitor dm(FolderMonitoringService); however when I try to do: FolderMonitoringService.run(); I get 2 c2143 errors. 1>d:\work\access for everyone\sibelius access\sibeliusaccessserver\utility.cpp(127): error C2143: syntax error : missing ';' before '.' 1>d:\work\access for everyone\sibelius access\sibeliusaccessserver\utility.cpp(127): error C2143: syntax error : missing ';' before '.' If I remove the typedef previously shown, this line: FolderMonitoringService.run(); Compiles fine, but the line: boost::asio::dir_monitor dm(FolderMonitoringService); will not compile giving c2061, solved with the typedef-thanks igor! I've tried boost.ref, with know success. The function signature of the dir_monitor's constructor is: explicit basic_dir_monitor(boost::asio::io_service &io_service) Dir_Monitor is typedef'd to be basic_dir_monitor. Can anybody please tell me why the run function is causing an issue and how to fix this issue. Regards Sean.

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[Fusion] Adapting template nested structure
by Kamil Renczewski 20 Feb '11

20 Feb '11

Hello I have a compilation error when using BOOST_FUSION_ADAPT_TPL_STRUCT on nested structure. namespace nsp { template< class T > struct Outer { struct Inner { int mint; }; }; } BOOST_FUSION_ADAPT_TPL_STRUCT( (T), (nsp::Outer::Inner) (T), (int, mint) ) Above code generates compiler errors on g++ 4.4.5. Am I doing something wrong? Or maybe BOOST_FUSION_ADAPT_TPL_STRUCT can't adapt nested structures? If so, how can I workaround this? -- best regards Kamil Renczewski

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