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how to link libraries in Jamroot?
by Arne Kalaghan 13 Jul '09

13 Jul '09

Hello, I am not very experienced with boost. I try to learn how to use the boost.thread library. After early bjam compilation errors (undefined references, because the boost_thread library was not linked), I found that this Jamroot creates my executable successfully: exe threadtest : threadtest.cpp : <library>/usr/lib/libboost_thread-gcc42-mt-1_34_1.so.1.34.1 ; Is it possible to simplify the <library> parameter to something like "boost_thread"? The reason is that I am developing on different systems with different boost versions, so that I don't want to hardcode the library version in the Jamroot. I thought that the boost.build system should be smart enough that it finds the appropriate library file if you only tell it "use the thread library please". How can I make the Jamroot independent from the boost installation and, more importantly, from the operation system? Best wishes, A. Kalaghan

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[array] GCC 4.2 warnings with array initialization
by Allen Cronce 13 Jul '09

13 Jul '09

Hi all, When building with boost 1.36 and GCC 4.2 under Xcode, the following code produces a warning: boost::array<int, 2> warningArray = { 1, 2 }; warning: missing braces around initializer for 'int [2]' We see no warnings with GCG 4.0. We have a zero warning tolerance. All warnings are counted as errors. The boost::array documentation indicates that the single brace approach should work for conforming compilers, according to 8.5.1 (11) of the Standard. So does that mean that GCC 4.2 is non-conforming? Sure enough, when I change the code to include a second set of braces, the warning is gone: boost::array<int, 2> noWarningArray = { { 1, 2 } }; But this is a problem as we move to GCC 4.2 because a) we use initialized arrays all over the place, so this means a lot of little changes, and b) requiring an extra set of braces is counter intuitive and irritating at best. I don't like the idea of making the above code changes, and I don't want to globally disable the warning because it might be useful for other code. Does anyone have a better solution? Thanks in advance for any suggestions. Best, -- Allen Cronce

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Why can I not put a break in this part of asio sample code?
by Ozgur Ozturk 13 Jul '09

13 Jul '09

Hi, I am using the async_tcp_echo_server.cpp<http://www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/echo/async…>sample code to understand asio. when I am tracing code in visual studio, it doeasn't let me put a breakpoint inside start() function in session class. Will it be run in another thread? is that the reason for not being able to put a breakpoint? Though it seems I can put breakpints for other codes that run in other threads... Why can I not put here? I tried to break at the point calling this function and step into from there. it jumps to async_receive(...) function in win_iocp_socket_service.hpp file. Could someone help me understand what is going on, or give me some pointers about how to trace such code? TIA, Ozgur PS: here is the related code: class session { //... //this is the part I can not put breakpoint. void start() { socket_.async_read_some(boost::asio::buffer(data_, max_length), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } Best regards, Ozgur (Oscar) Ozturk www.DrOzgur.com +1 (614) 805-4370

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[thread] thread specific variable instead of thread specific pointer?
by Frédéric Bron 13 Jul '09

13 Jul '09

I would like to have a variable specific to each thread. This means I would like to use the same variable name and that this name corresponds to different instances in different threads. For example, I would like to build a log stream that writes in different files in different threads. For example I would like to have a variable "flog" that behaves like a std::ostream: flog << "hello world!" ; I have found the two following solutions based on the use of boost::thread_specific_ptr but I am not fully satisfied with them: boost::thread_specific_ptr<std::ofstream> flogs ; // first solution using a function std::ostream &flog() { return *flogs.get() ; } // but I then have to add () after flog: flog() << "hello world!" ; // second solution using a macro #define flog flog() // but macros are not very recommended in C++. Any other idea that would allow me to write flog << "hello world!" like with std::cout? Note that I also tried to write a class derived from ostream with only one instance flog. This class had a special stream buffer using a thread specific pointer. However, the flog instance stores some informations like the precision of real numbers (flog << setprecision(10) for example) and the output of one thread can then interfere with the output of other threads... Regards, Frédéric

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Some of Boost Regex++ not recognized
by lsimons 13 Jul '09

13 Jul '09

<hoping this isn't a double post. Had some trouble with connection first time> I really appreciate the work done on the Boost libraries. I've used them in other projects and it's always been a welcome relief. For my current project, I'm trying to use the Boost Regex++ library in MSVC++ 6.0 (under Vista) to do some basic regex. I've installed the libraries as per the tutorial and added the Boost path to my compiler and linker includes. A lost of the basic functionality works fine, but I'm having trouble with autocompletion. The bigger issue is that certain parts of the library seem to throw the compiler. Ex that comiples fine: #include "stdafx.h" #include <boost/regex.hpp> #include <string.h> using namespace std; using namespace boost; int main(int argc, char* argv[]) { regex expr("^&[a-zA-Z0-9_ ]+,\\s+[a-zA-Z0-9_ ]+,\\s+[0-9].+"); string text = "&AirSpeed_Error, tla_error, 2 \\test stuff"; bool result; result = regex_match(text,expr); if (result == true) cout << "Match" << endl; else cout << "No Match" << endl; return 0; } If I add the line "match_flag_type flags = match_default;" I receive three errors: C:\Users\me\Documents\test\test.cpp(30) : error C2065: 'match_flag_type' : undeclared identifier C:\Users\me\Documents\test\test.cpp(30) : error C2146: syntax error : missing ';' before identifier 'flags' C:\Users\me\Documents\test\test.cpp(30) : error C2065: 'flags' : undeclared identifier Error executing cl.exe. I think I might simply have something misconfigured in MSVC6, and I would appreciate any comments or suggestions towards resolving the issue. Please let me know if there's any additional info I can provide. Thanks, Louis -- View this message in context: http://www.nabble.com/Some-of-Boost-Regex%2B%2B-not-recognized-tp24219036p2… Sent from the Boost - Users mailing list archive at Nabble.com.

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[filesystem] Extracting a relative path.
by Robert Jones 13 Jul '09

13 Jul '09

Hi All I'm trying to understand how to determine the relative path of one absolute path to another. So, c:\a\b\c.d relative to c:\a and I'd like the answer to be b\c.d I thought this would be easy to do, but I can't see how. Any thoughts? Thanks, Rob.

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[Tuple] What's the point?
by Robert Jones 13 Jul '09

13 Jul '09

I know that sounds like a slightly flippant question, but I really don't get it. I've used tuples a few times, always for the multiple return value behaviour using tie( ), but in the end it always seems to be a better solution to use a struct. Code like t.get<1>( ) = "fred"; is a bit non-obvious, compared to t.forename = "fred"; So have I entirely missed the point of tuples? Thanks, Rob.

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understanding placeholders
by Ozgur Ozturk 13 Jul '09

13 Jul '09

Hi, I see in the code some functions are passed things like boost::asio::placeholders::bytes_transferred. But I didn't understand what is going on, what are their aim? I found they are defined in placeholders.hpp as boost::arg<2>& bytes_transferred = boost::asio::placeholders::detail::placeholder<2>::get(); //and the get function as template <int Number> struct placeholder { static boost::arg<Number>& get() { static boost::arg<Number> result; return result; } }; TIA, Best regards, Ozgur (Oscar) Ozturk www.DrOzgur.com +1 (614) 805-4370

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Deadline_timer problem
by Mario Chacon 13 Jul '09

13 Jul '09

Hello: I have a problem using boost deadline timer that I cannot resolve. Why the resume method do not call again to the handler method??? Do I have something wrong? class TimerCallback { public: virtual void OnTimer()=0; }; class Timer : boost::noncopyable { public: Timer(unsigned long timeOutMilliSeconds, TimerCallback* callbac) : m_scheduler(), m_timer(m_scheduler), m_timerThread(), m_callbac(callbac), m_timeOutMilliSeconds(timeOutMilliSeconds) { }; virtual ~Timer() { m_scheduler.stop(); m_timerThread->join(); }; void some_operation() { //m_scheduler.post(boost::bind(m_callbac->OnTimer(), this)); m_callbac->OnTimer(); }; void handler(const boost::system::error_code& error) { if (!error) { // Timer expired. m_callbac->OnTimer(); m_timer.expires_from_now(boost::posix_time::milliseconds(m_timeOutMilliSeconds)); // Start an asynchronous wait. m_timer.async_wait(boost::bind(&Timer::handler, this, boost::asio::placeholders::error)); } } void start() { // Set an expiry time relative to now. m_timer.expires_from_now(boost::posix_time::milliseconds(m_timeOutMilliSeconds)); // Start an asynchronous wait. m_timer.async_wait(boost::bind(&Timer::handler, this, boost::asio::placeholders::error)); m_timerThread.reset(new boost::thread(boost::bind(&boost::asio::io_service::run, &m_scheduler))); } void pause() { m_timer.cancel(); }; void resume() { m_timer.expires_from_now(boost::posix_time::milliseconds(m_timeOutMilliSeconds)); m_timer.async_wait(boost::bind(&Timer::handler, this, boost::asio::placeholders::error)); }; private: boost::asio::io_service m_scheduler; boost::asio::deadline_timer m_timer; boost::scoped_ptr<boost::thread> m_timerThread; TimerCallback* m_callbac; unsigned long m_timeOutMilliSeconds; }; Salu2.. masch...

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building boost libraries for cross-compiled project
by Steve Drake 13 Jul '09

13 Jul '09

I am trying to use boost (specifically the regex part) in a cross-compiled environment. The target is a single board computer running Linux on ARM. My development computer is a Windows 2000 machine. The cross compiler is a GNU C++ compiler that I got from the SBC vendor. It is located here: c:\TechnologicToolchain\devel-tools\crosstool-cygwin\bin\arm-unknown-linux-g nu-g++.exe When I build my ARM application program, by PATH on the PC is set to this: c:\TechnologicToolchain\devel-tools\crosstool-win\bin; \ c:\TechnologicToolchain\devel-tools\crosstool-cygwin\bin; \ c:\TechnologicToolchain\devel-tools\cygwin How do I build the boost libraries on my development PC so I can link them with my cross-compiled application code and run them on the ARM target? I am unfamiliar with bjam so I am having trouble figuring out how to configure it to use a specific compiler executable. Thanks in advance for any suggestions. Steve

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