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event loop
by Jens Luedicke 24 Jan '09

24 Jan '09

Hello, is there something like a generic event loop library in boost? Jens -- Jens Luedicke web: http://perldude.de

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Re: [Boost-users] Tree library?
by joel falcou 24 Jan '09

24 Jan '09

Le Sam 24 janvier 2009 10:51, Thomas Klimpel a écrit : > Are you sure? The original poster seems to have a "rooted tree" in mind, > which is a special "directed acyclic graph" (DAG). I just looked at the > TOC of the boost::graph documentation, and the only DAG algorithm I could > find was "topological_sort". There is also the transitive_closure > algorithm, which could be used to compute the "partial order" relation of > the DAG, but I'm not sure whether this is really the appropriate way to > compute the "partial order" relation of a DAG (because the number of > edges could increase to O(V^2) and DAG's are not mentioned in the > corresponding documentation). Indeed, I wasn't thinking of the related algorithm. So yeah, boost::tree seems to lack then

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boost::interprocess::message_queue::timed_receive, bug or mistake?
by nacitar＠ubercpp.com 24 Jan '09

24 Jan '09

I'm using boost svn 50746 (latest at time of writing), on 32-bit Ubuntu Intrepid Ibex, with gcc/g++ 4.3.2 This is a simple test case showing that for some reason, message_queue::timed_receive is returning immediately for me, not throwing an exception, but just returning false which signifies that the timeout has been reached. The output of the program is as follows: Current time: 2009-Jan-23 17:40:29 After delay: 2009-Jan-23 17:40:34 Timeout at 2009-Jan-23 17:40:29 Note that the timeout occurs before it is supposed to, it returns instantly. Is this a bug, or am I doing something wrong? MINIMAL CODE: #include <iostream> #include <boost/interprocess/ipc/message_queue.hpp> #include <boost/date_time/posix_time/posix_time.hpp> // Link with boost_date_time int main(void) { char buf[1024]; std::size_t uSize; unsigned int priority; // Create a queue boost::interprocess::message_queue::remove("SOME_QUEUE"); boost::interprocess::message_queue mq(boost::interprocess::create_only,"SOME_QUEUE",1024,1024); // 5 second delay boost::posix_time::time_duration delay(boost::posix_time::seconds(5)); // current time boost::posix_time::ptime timeout = boost::posix_time::ptime(boost::posix_time::second_clock::local_time()); std::cout << "Current time: " << boost::posix_time::to_simple_string(timeout) << std::endl; timeout += delay; std::cout << "After delay: " << boost::posix_time::to_simple_string(timeout) << std::endl; if (mq.timed_receive(buf,sizeof(buf),uSize,priority,timeout)) { std::cout << "Got a message!" << std::endl; } else { std::cout << "Timeout at " << boost::posix_time::to_simple_string(boost::posix_time::ptime(boost::posix_time::second_clock::local_time()))<< std::endl; } return 0; }

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Preserving mtime with filesystem lib
by Brad Schick 24 Jan '09

24 Jan '09

Is there a portable way to use the boost filesystem library to copy files and preserve mtimes? I am writing a tool that moves media files around and mtime can be significant when other sources of metadata are absent (like exif, iptc, xmp). It would be a bummer to have to add platform specific code to do that. Thanks, -Brad

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Using different compilers with boost.
by Dan Smithers 23 Jan '09

23 Jan '09

Hi, I need to use several compilers for my project for different target computers. I have built boost 1.37 for gcc 4.1.2 and 3.4.3 and everything seems to be nicely set up as <boost_dir>/lib/libboost_xxx-gcc34-mt-1_37.so and <boost_dir>/lib/libboost_xxx-gcc41-mt-1_37.so. Is there anyway of automatically detecting which version to link? I suppose that gcc --version and some sort of awk script could do this. thanks dan

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How does one build a "release" version of Boost with the -Zi or /Zi compiler flag enabled?
by Joseph A. Marks 23 Jan '09

23 Jan '09

How does one build a "release" version of Boost with the -Zi or /Zi compiler flag enabled? Please e-mail answer directly to josephamarks(a)yahoo.com As well as to this list! Thanks Very much. Joseph A. Marks PHONE: 612-788-9658 e-mail: josephamarks(a)yahoo.com

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Re: [Boost-users] 1.37: boost::enable_shared_from_this fails whil estd::tr1 succeed s
by Daniel Lidström 23 Jan '09

23 Jan '09

> Daniel Lidström: > > I have already found a workaround, but it is a little bit annoying: > > > > struct Sub : public Base, > > public tr1::enable_shared_from_this<Sub> > > { > > void f() > > { > > BasePtr basePtr = > > tr1::dynamic_pointer_cast<Base>(shared_from_this()); > > } > > }; > > > > I would like to avoid explicit type casts like this. > > You don't need the cast. Of course. Sorry I didn't see the obvious this time. /Daniel

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[date time] Querying current time zone settings.
by Rodolfo Federico Gamarra 23 Jan '09

23 Jan '09

Hi all! I'm using boost::posix_time::second_clock::local_time() to retrieve my current local time, and then using operator<< to stream the resulting ptime. I'd like to add to the output my local time zone (as configured in the underlying OS). Be it just a time difference or (better) a region (like "America/New_York"). I have been looking but didn't find how to to it. The class ptime doesn't include the time zone; and all the other examples I've seen in to docs work with an explicitly used time zone in the code. For example: time_zone_ptr zone( new posix_time_zone("MST-07") ); local_date_time ldt = local_sec_clock::local_time(zone); And, for instance, in the docs about I/O it can be seen "%q ISO time zone (output only). This flag is ignored when using the time_facet with a ptime.". There's also a boost::date_time::c_local_adjustor (which warns about "This class assumes that timezone settings of the machine are correct. This can be a very dangerous assumption."), but doesn't help me much. By now, I can use (also) boost::posix_time::second_clock::universal_time() to infer my time zone. Is there any alternative to this? Thanks a lot. -- Rodolfo Federico Gamarra

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how to make a vector to derivedClass::create() methods
by Victor.Whiskey.Yankee 23 Jan '09

23 Jan '09

Hi, I wish to make a std::vector to some create() methods from several different derived classes (same ABC). I could instead use the ctors if necessary. lambda::bind<> and lambda::constructor<> maybe?, but I fail getting syntax. Thank you, Vic

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1.37: boost::enable_shared_from_this fails while std::tr1 succeed s
by Daniel Lidström 23 Jan '09

23 Jan '09

Hello, this sample does not compile when using the boost version: #if 1 #include <boost/enable_shared_from_this.hpp> namespace tr1 = boost; #else #include <memory> namespace tr1 = std::tr1; #endif namespace { struct Base { virtual void f() = 0; }; typedef tr1::shared_ptr<Base> BasePtr; struct Sub : public Base, public tr1::enable_shared_from_this<Base> { void f() { BasePtr basePtr = shared_from_this(); } }; } int main() { return 0; } boost\enable_shared_from_this.hpp(50) : error C2446: '==' : no conversion from 'boost::enable_shared_from_this<T> *const ' to '`anonymous-namespace'::Base *' with [ T=`anonymous-namespace'::Base ] Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast boost\enable_shared_from_this.hpp(48) : while compiling class template member function 'boost::shared_ptr<T> boost::enable_shared_from_this<T>::shared_from_this(void)' with [ T=`anonymous-namespace'::Base ] test.cpp(23) : see reference to class template instantiation 'boost::enable_shared_from_this<T>' being compiled with [ T=`anonymous-namespace'::Base ] The tr1 version compiles though. I am using Visual Studio 2008 with SP1 installed. I have already found a workaround, but it is a little bit annoying: struct Sub : public Base, public tr1::enable_shared_from_this<Sub> { void f() { BasePtr basePtr = tr1::dynamic_pointer_cast<Base>(shared_from_this()); } }; I would like to avoid explicit type casts like this. Why does the boost version fail? Thanks in advance! Regards, Daniel Lidström Stockholm, Sweden

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