October 2012 - Boost-users - lists.preview.boost.org

[units] Missing quantity operator++, operator%
by Nathan Crookston 25 Oct '12

25 Oct '12

All, I'm in the process of switching my homegrown units system over to boost units. Some operators which I'm missing are the modulus and the pre and post increment operators. Looking through the archives I note an original review[1] which mentioned the absence of those operators. One response claimed that quantity<si::length, int> t = 5. ...; t++; was nonsensical as writing 5 m + 1, and the reviewer eventually agreed, citing possible confusion if the quantity type converted the initializer. Matthias Schabel seemed to respond favorably: 'I debated this for a while - the only problem is that there will be some value types with heterogeneous operator+ / operator- for which q + 1 is not the same type as q, but I guess that it is just OK for it to just give a compile error in those cases.' And Steven Watanabe said 'Will do.' I haven't found anything regarding the modulus operator. My question is, would a patch adding those operators be accepted? Thanks, Nate [1] http://lists.boost.org/Archives/boost/2007/03/119001.php

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Errors when linking a CXX executable to boost static libraries, using gcc4.7 and boost 1.51.0
by camille chambon 25 Oct '12

25 Oct '12

Hello, I'm trying to link a CXX executable to boost static libraries. My environment is: - Fedora 17 64bit - gcc 4.7 - boost 1.51.0 built with gcc 4.7 I then get the following errors : `.text._ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED2Ev' referenced in section `.text._ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED1Ev[_ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED1Ev]' of /home/cchambon/libs/lib/libpgma.a(Timeline.cpp.o): defined in discarded section `.text._ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED2Ev[_ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED5Ev]' of /home/cchambon/libs/lib/libpgma.a(Timeline.cpp.o) `.text._ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED2Ev' referenced in section `.text._ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED1Ev[_ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED1Ev]' of /home/cchambon/libs/lib/libpgma.a(DistributionFactory.cpp.o): defined in discarded section `.text._ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED2Ev[_ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED5Ev]' of /home/cchambon/libs/lib/libpgma.a(DistributionFactory.cpp.o) error: collect2: ld returned 1 exit status Does anyone know what these errors mean? Cheers, Camille

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Re: [Boost-users] Occasional blocking with tcp::socket::receive
by Stuart Siegel 25 Oct '12

25 Oct '12

I have read the documentation :-) My understanding is that it's blocking if there's no data left to be read and you ask it to read from the socket. In my case, the server has sent the data and it's there waiting for it to read. I've confirmed this via wireshark and, as I mentioned, the plain POSIX call to read (which is also blocking by the way) works as expected. ________________________________ From: nullable.type <nullable.type(a)gmail.com> To: boostusers(a)googlegroups.com Cc: "boost-users(a)lists.boost.org" <boost-users(a)lists.boost.org>; boost-users(a)lists.boost.org; ssiegel95(a)yahoo.com Sent: Thursday, October 25, 2012 3:34 AM Subject: Re: [Boost-users] Occasional blocking with tcp::socket::receive Hi Read the documentation: http://www.boost.org/doc/libs/1_51_0/doc/html/boost_asio/reference/basic_st… A call to boost::asio::ip::tcp::socket::receive(..) IS a blocking call. If you wannt to avoid blocking, just use the async_* functions. Cheers, Simon On Friday, October 19, 2012 3:50:11 PM UTC+2, Stuart Siegel wrote: The call to receive below will occasionally hang. All interactions are synchronous and single threaded. Things work perfectly if I use the alternative <sys/socket.h> (POSIX) implementation under the #else. Since I'm pretty new to boost::asio, I must be doing something wrong but after many hours of trying different things, I'm still stuck. Any advice would be appreciated. #if 1 namespace bas = boost::asio; remaining = X //(something typically about 5000 bytes of char data) bas::streambuf b; bas::streambuf::mutable_ buffers_type bufs = b.prepare(1024); while (remaining > 0) { size_t n = sock.receive(bufs); //<-------------this blocks every so often remaining -= n; for ( bas::buffers_iterator<bas:: streambuf::mutable_buffers_ type, char> it = bas::buffers_begin(bufs); it < (bas::buffers_begin(bufs) + n); it++ ) qba.append(*it); } #else //this works perfectly in the 250000 or so test calls I've hit it with char buf[1024]; while (remaining > 0) { n = read( sock, buf, min( sizeof(buf), remaining ) ); remaining -= n; for (int i = 0 ; i < n; i++ ) qba.append(buf); } #endif >

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Are shared_mutex's recursive?
by John M. Dlugosz 25 Oct '12

25 Oct '12

Clearly recursive acquiring of a shared (reading) lock is natural. But what about an exclusive lock? Can the owning thread acquire the write lock recursively, or even read locks recursively?

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Memory usage of adjacency_list
by Ed Linde 24 Oct '12

24 Oct '12

Hi, Is it possible to get a ballpark figure of the maximum memory required for an adjacency_list, given its settings? I need these statistics to report how much memory is being used initially when reading in a large graph and then after vertex removal operations and edge removal operations, how much reduction is got in this memory finally. Do I have to write something of my own to do this? Thanks, Ed -- View this message in context: http://boost.2283326.n4.nabble.com/Memory-usage-of-adjacency-list-tp4637051… Sent from the Boost - Users mailing list archive at Nabble.com.

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Is it possible to put a std::unique_ptr into a mulit_index container?
by Josh Quigley 24 Oct '12

24 Oct '12

Hi all, Is it possible to put a std::unique_ptr into a mulit_index container? In particular, the following fails. typedef std::pair<int, std::unique_ptr<int> > ValueT; typedef boost::multi_index_container< ValueT, boost::multi_index::indexed_by< boost::multi_index::hashed_unique< BOOST_MULTI_INDEX_MEMBER(ValueT, int, first) > > > HashMap; HashMap map; auto a = std::make_pair(5, std::unique_ptr<int>(new int(5))); map.insert(std::move(b)); // This line fails to compile (Visual Studio 2012) I'm guessing the answer is 'No' and it's because the rvalue reference overloads have not been done, but I'd like confirmation (or even better, to be told I'm wrong!). Thanks, Josh.

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[spirit] Parsing quoted string
by Giampiero Gabbiani 24 Oct '12

24 Oct '12

Hi together, I have to parse the following row: "a_token": true|false, the last comma is optional. Testing the following: bool value; test_parser(" \"orig_bool\": true,", qi::lit('"') >> *(ascii::alnum | qi::char_('_')) >> qi::lit('"') >> qi::lit(':') >> boost::spirit::qi::bool_[phx::ref(value)=_1] >> -(qi::lit(','))); it works, but with the following instead the program compile but hangs ... bool value; test_parser(" \"orig_bool\": true,", qi::lit('"') >> *(!qi::lit('"')) >> qi::lit('"') >> qi::lit(':') >> boost::spirit::qi::bool_[phx::ref(value)=_1] >> -(qi::lit(','))); the only difference is the way by means I get the content of the quoted string, actually instead of using *(ascii::alnum | qi::char_('_')) I'd like to use *(!qi::lit('"')) that - imho - should be better but it actually hangs. What/where am I actually missing/wrong? Many thanks in advance Giampiero

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Re: [Boost-users] asio: how to handle disk IO, recommendations
by Avi Bahra 24 Oct '12

24 Oct '12

> Currently I has a single threaded server based on boost ASIO. > This works correctly most of the time. > However on systems where i know that the disk's are slow. > , the server grinds to a halt, when dealing with the blocking > disk IO. > > I could not find any examples or documentation in ASIO, in > how to get round these issues. It appears that ASIO does > not provide any support for async' disk IO. > > So I assume this is handled by use of threads ? > Are there any examples of using ASIO with threaded disk IO, > since this must be very common use case ? > > Is the strand functionality appropriate for handing disk IO, > in an async' manner. > > Any recommendations/advice on this issues would be > greatly appreciated. > > Best regards, > Ta, > Avi > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > >Hi Avi, > >If your server performs short read/writ frequently and data to be transfer >to network depend on these operations, then multi-threading does not help a >lot here. I would suggest you to recheck your I/O strategies and make sure >they are optimized. e.g. buffering, cache, .. etc. If they are perfect but >performance still bother you, then consider to use memory mapped file or >libaio. > >Best, >Acer. In my case the ASIO server needs to only write to a local disk.(no reads) One write is relatively short, i.e to a log file, to record all requests, the other is to write periodically a in memory node tree. This can vary between 1-100MB. My thinking was that if I used a thread reserved for writing the node tree, it will not block the server from handling requests, on slow file systems. I will look into memory mapped files and libaio. Ta, Avi

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serialization
by Larry E. Ramey 24 Oct '12

24 Oct '12

I've got a system where class A { A(); A(const string&); virtual ~A(); }; class C : public A { C(); C(const A&, float); virtual ~C(); }; BOOST_CLASS_EXPORT( A ) BOOST_CLASS_EXPORT( C ) main() { ... const A* a = new a("stuff"); const C* c = new c(*a, 52.54390f); { ofstream ofs("dump.bin"); boost::archive::text_oarchive oa(ofs); oa<<a<<c; } ... A* a2=NULL; C* c2=NULL; try { ifstream ifs("dump.bin"); boost::archive::text_iarchive ia(ifs); ia>>a2; ia>>c2; } catch(boost::archive::archive_exception& ae) { cout<<ae.what(); } } This works just fine. If I replace A* a2=NULL; C* c2=NULL; with A* a2=NULL; A* c2=NULL; Then it throws an unregistered_class exception. If I change the iarchive to take: const A* a = new A("I'm cool"); const A* c = new C(*a,54.2f); then I can unarchive it with a pair of A*. Is this by design? Seriously? I can't save derived pointers and unarchive base pointers? Larry

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adding 'blackberry' to boost build
by Gottlob Frege 23 Oct '12

23 Oct '12

I work for RIM (ie BlackBerry), and am trying to make using boost as easy as possible to use for BB developers. So I would like to make building boost for BB as easy as possible. I would also like to make building boost work "as expected" for anyone who understands Boost.Build. It is the "as expected" part that I'm not sure of. ie should I just offer a blackberry-config.jam? should Boost.Build be changed to auot-detect the BB NDK? should blackberry be a toolset? a target-os? ...? how would you *expect* it hook into Boost.Build? (And note that I expect that developers *also* use the same boost for Windows, etc, so I don't want to replace/affect the simple build for the host machine.) - And finally, it would be nice if this was upstreamed back into boost build (if people think that makes sense), so that boost "just works" on BlackBerry. Here's what I have so far: from the command line, you run something like: b2 install --prefix=C:\boost\ --user-config=blackberry-config.jam --layout=system toolset=gcc target-os=qnxnto I'd prefer it if they didn't need to type so much. And the config file looks like basically the rest of this email: import os ; # these env vars are set by installing the BB NDK QNX_TARGET_ARCH = [ os.environ QNX_TARGET_ARCH ] ; QNX_TARGET = [ os.environ QNX_TARGET ] ; QNX_HOST = [ os.environ QNX_HOST ] ; if ! $(QNX_TARGET) || ! $(QNX_HOST) { ECHO error: ; ECHO error: BlackBerry build of Boost requires QNX_TARGET and QNX_HOST env variables. Did you run bbndk-env.bat? ; ECHO error: ; EXIT ; } if $(QNX_TARGET_ARCH) = x86 { dashVOpt = gcc_ntox86_cpp ; linkArchDir = x86 ; } else { dashVOpt = gcc_ntoarmv7le_cpp ; linkArchDir = armle-v7 ; } using qcc # Version : # C++-compile-command : $(QNX_HOST)/usr/bin/QCC -V$(dashVOpt) # Compiler options : <compileflags>"-D__QNX__" <compileflags>"-D__QNXNTO__" # Add -D__USE_ISOC99 for rounding control mechanism (boost/numeric/interval/hw_rounding.hpp) <compileflags>"-D__USE_ISOC99" <compileflags>"-I$(QNX_TARGET)/usr/include" # Prevent this from being output: "note: the mangling of 'va_list' has changed in GCC 4.4" <compileflags>"-Wno-psabi" # Add -fPIC to link without error to LibTestNativeLibTuTest.o (for statechart tests) <compileflags>"-fPIC" # Requested by BBM team <compileflags>"-fno-strict-aliasing" # Functions like sync_val_compare_and_swap and sync_fetch_and_add aren't available <compileflags>"-DBOOST_SP_NO_SYNC" <linkflags>"-L$(QNX_TARGET)/$(linkArchDir)/usr/lib -L$(QNX_TARGET)/$(linkArchDir)/lib" ; import option ; option.set keep-going : false ; ------------------------ Thanks in advance, Tony

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