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

Is it ok to pass &my_boost_array_variable[2] into a C function expecting a Type*
by Anton Daneyko 29 Nov '12

29 Nov '12

Hi, I have a two variables: boost::array my_boost_array_variable_1<float, 3>; boost::array my_boost_array_variable_2<float, 3>; now I want to call a C function with the following signature: int MPI_Allreduce ( void *sendbuf, void *recvbuf, ...); I want to pass the address of a particular element of my my_boost_array_variable_1 and my_boost_array_variable_2 as a first and second parameter of MPI_Allreduce: MPI_Allreduce(&my_boost_array_variable_1[2], &my_boost_array_variable_2[2], ... or should I rather do: MPI_Allreduce(my_boost_array_variable_1.c_array() + 2, my_boost_array_variable_2.c_array() + 2, ... Thanks, Anton

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strange linkage problem with boost_date_time 1.52 (x86_64-linux-gnu/gcc version 4.7.2)
by mypop＠freenet.de 29 Nov '12

29 Nov '12

Hi erveryone, i have a little problem linking against my newly installed: boost_date_time library. I even don't know if this is the right place for this question because everything works fine so far in the past. 1. I never had problems compiling and linking this sources before (on 3 other systems). 2. The project also contains some other directories with some kind of commandline tools. These tools also link against the regex and date_time libraries without any problems. Here is the part where the libs are defined in my Makefile.am libmodwscmi_la_CXXFLAGS = $(INCLUDES) $(PROJECT_INCLUDES) $(APR_CFLAGS) libmodwscmi_la_LDFLAGS = $(LDADD) $(BOOST_LDFLAGS) $(LIB_BOOST_REGEX) $(LIB_BOOST_DATETIME) `$(APR1CONFIG) --link-ld --libs` libmodwscmi_la_LIBADD = $(top_builddir)/utils/mysqlpp/libmysqlpp.la $(top_builddir)/utils/jwsmtp/libjwsmtp.la After compiling is complete the linker gets called by this command: g++ -fPIC -DPIC -shared -nostdlib /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.7/crtbeginS.o .libs/libmodwscmi_la-mod_wscmi.o .libs/libmodwscmi_la-mod_gsoap.o .libs/libmodwscmi_la-mod_utils.o .libs/libmodwscmi_la-mod_mysql.o .libs/libmodwscmi_la-md5.o .libs/libmodwscmi_la-regEx.o .libs/libmodwscmi_la-utils.o .libs/libmodwscmi_la-exception.o .libs/libmodwscmi_la-dateTime.o .libs/libmodwscmi_la-validator.o .libs/libmodwscmi_la-mysqlPool.o .libs/libmodwscmi_la-mysqlCons.o .libs/libmodwscmi_la-mysqlQueries.o .libs/libmodwscmi_la-sqlite3.o -Wl,-rpath -Wl,/var/www/projects/mod_wscmi-1.0/utils/mysqlpp/.libs -Wl,-rpath -Wl,/var/www/projects/mod_wscmi-1.0/utils/jwsmtp/.libs -L/usr/local/lib -lboost_date_time -lboost_regex -L/usr/lib /usr/lib/libapr-1.so -L/usr/local/mysql/lib ../utils/mysqlpp/.libs/libmysqlpp.so ../utils/jwsmtp/.libs/libjwsmtp.so -L/usr/lib/gcc/x86_64-linux-gnu/4.7 -L/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../lib -L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.7/../../.. -lstdc++ -lm -lc -lgcc_s /usr/lib/gcc/x86_64-linux-gnu/4.7/crtendS.o /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu/crtn.o -pthread -O3 -Wl,-R/usr/local/lib -pthread -Wl,-soname -Wl,libmodwscmi.so.0 -o .libs/libmodwscmi.so.0.0.0 As you can see above, both libraries are present: -lboost_date_time -lboost_regex. They also can be found on the harddrive (in /use/local/lib): ... -rw-r--r-- 1 root 136876 Nov 20 09:19 libboost_date_time.a lrwxrwxrwx 1 root 28 Nov 20 09:18 libboost_date_time.so -> libboost_date_time.so.1.52.0 -rwxr-xr-x 1 root 94337 Nov 20 09:18 libboost_date_time.so.1.52.0 ... -rw-r--r-- 1 root 2619610 Nov 20 09:19 libboost_regex.a lrwxrwxrwx 1 root 24 Nov 20 09:18 libboost_regex.so -> libboost_regex.so.1.52.0 -rwxr-xr-x 1 root 1251576 Nov 20 09:18 libboost_regex.so.1.52.0 ... The complete build runs fine! There are no errors or warnings but the fianlly library is unusable because: boost_date_time is not present. Ldd shows up something like this: ldd .libs/libmodwscmi.so.0.0.0 linux-vdso.so.1 => (0x00007fff17da4000) libboost_regex.so.1.52.0 => /usr/local/lib/libboost_regex.so.1.52.0 (0x00007ff289006000) libapr-1.so.0 => /usr/lib/libapr-1.so.0 (0x00007ff288db5000) libmysqlpp.so.0 => /var/www/projects/mod_wscmi-1.0/utils/mysqlpp/.libs/libmysqlpp.so.0 (0x00007ff288b35000) libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007ff288832000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff288472000) libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ff28825c000) libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ff28803f000) libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007ff287e39000) libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ff287c35000) libmysqlclient.so.18 => /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 (0x00007ff2876f1000) libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ff2873f4000) /lib64/ld-linux-x86-64.so.2 (0x00007ff2895e9000) libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007ff2871dd000) Only libboost_regex.so.1.52.0 was linked in and i have absolutly no idea why: libboost_date_time does not show up. So maybe someone of the list can give me an adivse of what's is going on here. Thanks and greetings Michael --- E-Mail ist da wo du bist! Jetzt mit freenetMail ganz bequem auch unterwegs E-Mails verschicken. Am besten gleich informieren unter http://mail.freenet.de/mobile-email/index.html

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Fwd: [boost] [thread] Crash when calling pthread_cond_wait from thread.cpp in iOS simulator
by Brent Lewis 29 Nov '12

29 Nov '12

I've determined that pthread_cond_wait works fine on an iPhone (hardware) and works fine when called from my own module on simulator (I use boost::condition_variable, and since it's header only and calling pthread_cond_wait, it's my module) But when I create a new thread, which goes through thread.cpp in the thread library, call_once in once.hpp has to (sometimes, based on synchronization randomness) call pthread_cond_wait which results in the message: Detected an attempt to call a symbol in system libraries that is not present on the iPhone: (null) called from function _ZN5boost9call_onceIPFvvEEEvRNS_9once_flagET_ in image Blackjack If I make it continue, I get a problem report from OSX which tells me that the stack trace is: 0 libsystem_kernel.dylib 0x903a5a6a __pthread_kill + 10 1 libsystem_c.dylib 0x96afbacf pthread_kill + 101 2 libsystem_sim_c.dylib 0x03a0457b abort + 140 3 libSystem.dylib 0x032ad4ad _interposition_vtable_unimplemented + 200 4 libSystem.dylib 0x032c0938 pthread_cond_wait$UNIX2003 + 60 5 Blackjack 0x00277c8c void boost::call_once<void (*)()>(boost::once_flag&, void (*)()) + 156 (once.hpp:112) 6 Blackjack 0x0027506b thread_proxy + 139 (thread.cpp:135) 7 libsystem_c.dylib 0x96afa557 _pthread_start + 344 8 libsystem_c.dylib 0x96ae4cee thread_start + 34 Is it maybe some discrepancy in the settings I'm using to build boost that's causing to link something wrong... something else? I've attached the complete crash log. In case it is build related, this is how I've built boost using a shell script: LIBS=" --with-thread --with-serialization --with-date_time" CPLUS_INCLUDE_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneOS6.0.sdk/usr/include/ PATH=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:$PATH ./b2 toolset=darwin runtime-link=static link=static variant=release include=$CPLUS_INCLUDE_PATH cxxflags=--visibility=default cxxflags=-Wno-long-long --build-dir=$HOME/boost/lib/build --includedir=$HOME/boost/include --libdir=$HOME/boost/lib/build/arm-release architecture=arm target-os=iphone $LIBS -q install

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[counting_range] why?
by Robert Jones 28 Nov '12

28 Nov '12

Ok, maybe I'm having a senior moment here, but why is the second line wrong? Thx, Rob. #include <boost/range/counting_range.hpp> int main( ) { // Ok auto r = boost::counting_range( 0, 3 ); // Not Ok. auto s = boost::counting_range<int>( 0, 3 ); }

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[graph] File Dependency Example with updates
by Brian Budge 28 Nov '12

28 Nov '12

Hi all - I am toying around with the file dependency example that is part of the boost graph documentation as a way of adapting the concepts to my own use cases. What I want to do is update the graph over time (add more files with more dependencies), and incrementally decide what needs to be built, and in what order. It makes sense that doing a breadth-first search from a changed node will give me everything that might be affected; however, if I change many nodes, is there something better? I could imagine that I might mark nodes as they are encountered so that other BFS from other changed nodes won't traverse those as well. With boost graph, how can I control the BFS to stop recursion if a vertex has already been visited? I guess then once I have seen all the stale vertices, I can make a smaller graph that only has the stale vertices and their connections, and I can topologically sort the sub-graph to find the parallel build order? Sorry, I'm a bit out of practice with my graph algorithms in general, and I'm very new to the boost graph library, so I hope I haven't said anything dumb :) Any design suggestions welcome. Thanks, Brian

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Re: [Boost-users] [Who's using boost?] Algocoders : books on c++11, Boost and Beyond
by Erika James 27 Nov '12

27 Nov '12

On 28 November 2012 02:53, Algocoders . <algocoders(a)gmail.com> wrote: > > It is the pioneering efforts at boost towards "Using and Extending C++11, > Boost and Beyond" which has motivated us to devote ourself in developing > bullet-size capsules in the form of tiny booklets with industrial-set > framework to lift the thin veil with initial focus on practical usage of > C++11 vis-a-vis mathematical foundation behind it. > Wow, that's quite a mouthful! I read the excerpt of your first book on the website, and particularly enjoyed the final paragraph: *One thing was very much clear that, the naive looking interface* *was mere a rosy picture, hiding many unpleasant surprises in its bosom,* *which we thought of unfathoming it to its fullest. * I've never heard a C++ interface described as a bosom! I think you should rename the book to "Fifty shades of Boost"! ~Erika

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[Review] Review results for Coroutines
by Hartmut Kaiser 24 Nov '12

24 Nov '12

All, The review for the Coroutines library written by Oliver Kowalke started September 3rd 2012, and ended on September 12th 2012. I counted 7 votes, none of which were NO. All authors votes YES, some made additional requests. Overall, the verdict of the community was clear: Oliver Kowalke's Coroutines library is ACCEPTED The discussion was lively and it touched on several points. Design ------ The Coroutines library offers enormous potential for programming regimes such as communications software and embedded systems design. Oliver selected a sensible granularity for his design. This granularity allows for fine-tuning the implementations of cooperative scheduling mechanisms while avoiding the prohibitively heavy weight of preemptive scheduling that is found in POSIX and often in implementations of the C++11 thread support library. In particular, the separation of Coroutines from Context allows for porting to other systems with minimal effort and maximum reliability and code re-use. Some suggestion related to the API have been made during the review, most of which (if not all) have already been addressed. Oliver has a full list of things and works on integrating the suggestions. Here is a short list: - allow to specify the allocator to use for memory allocations inside the library - remove 'self' pointer and replace with TLS - add symmetric coroutines API - better support for generator functionality Naming ------ Some of the people participating in the discussions suggested not to use the abbreviated 'namespace coro', but to use the full 'namespace coroutines' instead. This again is not a precondition for acceptance. Documentation ------------- The consensus of almost everybody referring to the documentation was that it is terse but readable and sufficient. People suggested to integrate the docs of the old Coroutines library (written as an GSoC project by Giovanni P. Deretta) into the documentation of the reviewed library. I would like to thank all who participated in the discussions. Regards Hartmut --------------- http://www.cct.lsu.edu/~hkaiser http://stellar.cct.lsu.edu http://boost-spirit.com

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Re: [Boost-users] [Range & c++0x Lambdas] Can this be done?
by John M. Dlugosz 24 Nov '12

24 Nov '12

------------------------------ Message: 3 Date: Thu, 22 Nov 2012 11:31:05 -0800 From: "Jeffrey Lee Hellrung, Jr." <jeffrey.hellrung(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [Range & c++0x Lambdas] Can this be done? Message-ID: <CANvXPuQmePirYFadBKRyVoQur1N8DH2c-QhwqHgZMV2MNfG_gQ(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" > Maybe this is what you did, so I might not be suggesting something new, > but... Perhaps boost::result_of could have an extra conditional logic > branch added to it: I don't recall the details, but I've learned that result_of has compatibility issues with old/new ways in general. So, if the "old way" is published at all, use it (for backward compatibility, in case it is different from what decltype would detect). This allows lamdas and other code that assumes decltype is being used, while preseving the behavior of code that explicitly publishes the type. > - If F::result_type exists, return F::result_type; > - Else: << same as before >> Meanwhile, for different reasons, I made a macro that abstracts the >> different syntax between C++11 lambdas and Apple Block Closures. The latter >> generates a suitable lambda class complete with result_of member. That >> makes me think that you could have a macro that wraps a compiler-generated >> lambda expression in another class that inherits the operator() etc. and >> adds in the result_of typedef to simply use decltype. >> > Wouldn't that require defining a class at expression scope? Is that > possible? > > - Jeff > Here's my docs on the matter: Given a macro M, at its simplest M can expand to either [=] or ^ depending on the platform, and then be followed by the optional lambda-declarator and compound-statement. However, Apple's Blocks do not have proper value semantics. You must call a function on it before leaving the scope where it was defined, if it is to be used outside of that scope. And then it needs to be explicitly destroyed when it is no longer needed. In order to use it transparently in C++, it needs to be wrapped in an object with a destructor, (and that wrapper can take care of the initial function call too). But we don't want to have to inject anything _after_ the compount-statement, or the macro syntax would be difficult, requiring either fully-bracketing macros or double parens around the whole thing. Meanwhile, the wrapper object needs to be templatized to provide the correct typed operator() forwarding function. My (JMD's) solution is to use an operator, which can take a second argument as trailing text without being wrapped in parens. That is, M would expand to dummy| ^ so that after the trailing text (not seen by the macro) you get: dummy| ^(ARGLIST){BLOCK} that is, the completed Apple Block Literal Expression becomes the second argument of the operator|, and my special object is the first argument. The operator| can be a template, and break open the Block type in the same manner as can be done for normal function pointer declarations. For wrapping a C++ lambda, reason is different (add the decltype) but you still return an instance of a class with the right stuff in it. The return value is a templated type, wrapper0<Ret>, wrapper1<Ret,A1>, or wrapper2<Ret,A1,A2> (etc) (an emulation of "..." for some fixed number of arguments) So, the _type_ is not unique, but reused for each time the same operator() is needed. The instance holds the underlying (wrapped) instance as a member. For Apple Blocks, that is just their variation on a function pointer, so the type goes with the signature. To wrap C++11 lamdas, the underlying instance has a unique type. So use _that_ as the template argument, and generate another unique type that you can inherit from. Using an operator| to add the wrapper, you can explicitly pull it in when needed along with any other filters that are being applied.

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"cross-running" boost tests
by Gottlob Frege 23 Nov '12

23 Nov '12

I've managed to cross-compile boost for BlackBerry10 devices. (Side-note: there is very little docs on cross compiling) Now, how would I go about "cross-running" the boost tests? In particular, can I hook into the unit-test and/or run rules of Boost.Build? Given a command line, I can load and run it on device and then retrieve the results, I just need to know where to hook in. Tony

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Re: [Boost-users] "cross-running" boost tests
by Lemay.Steve 23 Nov '12

23 Nov '12

Can you share how you succeeded a cross compiling the tests, I didn't have luck. - Sent via iPhone -----Original Message----- From: Gottlob Frege [gottlobfrege(a)gmail.com<mailto:gottlobfrege@gmail.com>] Sent: Thursday, November 22, 2012 12:28 PM Pacific Standard Time To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] "cross-running" boost tests That is along the right track. But I don't want to have to do that for every boost test file. This isn't for my own tests, I want to run the boost tests. I sort of need a global launcher that I can hook into. On Thu, Nov 22, 2012 at 1:40 PM, Paulo Márcio Figueiredo Alves <pauloalves1986(a)gmail.com<mailto:pauloalves1986@gmail.com>> wrote: You could use testing.launcher, like this: b2 testing.launcher=my_custom_launcher It'll call my_custom_launcher to run your tests. On Thu, Nov 22, 2012 at 4:28 PM, Gottlob Frege <gottlobfrege(a)gmail.com<mailto:gottlobfrege@gmail.com>> wrote: On Thu, Nov 22, 2012 at 1:11 PM, Vicente J. Botet Escriba <vicente.botet(a)wanadoo.fr<mailto:vicente.botet@wanadoo.fr>> wrote: Le 22/11/12 16:51, Gottlob Frege a écrit : I've managed to cross-compile boost for BlackBerry10 devices. (Side-note: there is very little docs on cross compiling) Now, how would I go about "cross-running" the boost tests? In particular, can I hook into the unit-test and/or run rules of Boost.Build? I guess you should see how Boost.Build could support this. Best, Vicente Right. That's kind of what I'm asking. Does Boost.Build support this already? Is there a way to hook into 'run'? I don't find Boost.Build (or docs) easy to use/understand, so my poking around at it didn't find anything, but I could have easily missed it. Tony _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org<mailto:Boost-users@lists.boost.org> http://lists.boost.org/mailman/listinfo.cgi/boost-users _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org<mailto:Boost-users@lists.boost.org> http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Re: [Boost-users] list serialization with boost
by Brian Wood 22 Nov '12

22 Nov '12

Krzysztof Czainski: >2012/11/22 Olivier Austina <olivier.austina(a)gmail.com> > >> Hello, >> I am a newbie of boost and I want to use it. I would like to serialize a >> list. The list is defined with the following data type: >> >> typedef struct person { >> char *name; >> char *first_name; >> struct person *next; >> } person; >> >> person *list_person; >> > > I'd suggest reorganizing your struct into struct person { std::string > first_name; } and useing std::list<person> list. Then serializing and > other operations would probably be trivial. Shalom Another option would be an intrusive list -- http://www.boost.org/doc/libs/1_52_0/doc/html/intrusive.html . The serialization library in Boost doesn't provide support for intrusive containers, but the C++ Middleware Writer -- http://webEbenezer.net has support for intrusive list and rbtree. If you use std::list, the C++ Middleware Writer has some advantages -- http://webEbenezer.net/comparison.html over the serialization library in Boost. (There are serialization and deserialization tests with std::list there.) -- Brian Ebenezer Enterprises -- so far G-d has helped us. http://webEbenezer.net (651) 251-9384

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[mpl] How to use not_ with has_trivial_destructor metafunction
by Christian Henning 22 Nov '12

22 Nov '12

Hi there, I have troubles compiling the following code with Visual C++ 2010 and boost 1.52. #include <boost/mpl/not.hpp> #include <boost/type_traits/has_trivial_destructor.hpp> #include <boost/utility/enable_if.hpp> template <typename T> void foo( typename boost::enable_if< boost::mpl::not_< boost::has_trivial_destructor< T > > >::type* /*ptr*/ = 0 ) { int i = 9; } int main(int argc, char* argv[]) { foo< int >(); return 0; } The error I'm getting is: error C2770: invalid explicit template argument(s) for 'void foo(boost::enable_if<boost::mpl::not_<boost::has_trivial_destructor<T>>>::type *)' Can someone see what the problem might be? Thanks, Christian

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[Range & c++0x Lambdas] Can this be done?
by Robert Jones 22 Nov '12

22 Nov '12

Can the last line, labelled NOT Ok, be made to work? I think the lambda does not publish its result as a bind does, so I suspect it's hopeless. Any thoughts? Thx, Rob. #include <boost/range/adaptor/transformed.hpp> #include <boost/range/algorithm_ext/push_back.hpp> #include <boost/bind.hpp> #include <vector> #include <algorithm> struct S { int i; }; void f( std::vector<int> & out, std::vector<S> & in ) { using boost::adaptors::transformed; // Ok std::transform( in.begin( ), in.end( ), std::back_inserter( out ), bind( & S::i, _1 ) ); // Ok boost::range::push_back( out, in | transformed( bind( & S::i, _1 ) ) ); // Ok std::transform( in.begin( ), in.end( ), std::back_inserter( out ), []( S & s ) { return s.i; } ); // NOT Ok boost::range::push_back( out, in | transformed( []( S & s ) { return s.i; } ) ); }

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list serialization with boost
by Olivier Austina 22 Nov '12

22 Nov '12

Hello, I am a newbie of boost and I want to use it. I would like to serialize a list. The list is defined with the following data type: typedef struct person { char *name; char *first_name; struct person *next; } person; person *list_person; I have the list built from this structure and I want to serialize it on the hard disk. -- Regards Austina

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[Intrusive] unordered_set and thread safety
by Alexandre Hamez 22 Nov '12

22 Nov '12

Hello, I'm currently using intrusive:: unordered_set in a single threaded application. But now, I need to switch to a multi threaded application. As such, the unordered_set must be protected. I don't want to block the whole table with a single mutex. Thus, it would be fine to have a lock per bucket. Furthermore, intrusive:: unordered_set provides a bucket_traits mechanism to enable some customization. So, my question: is it possible to use bucket_traits to have a lock per bucket? Thank you! -- Alexandre Hamez

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Errors compiling with Boost
by Amos Anderson 21 Nov '12

21 Nov '12

Hello -- I'm having trouble compiling our code on redhat gcc 4.4.6 (full specs below). There are a lot of errors in the output, but paring down the list a bit, some examples are pasted below. This exact same code successfully compiles on several OSX compilers, as well as redhat gcc 4.1.2. I posted this to Boost.Build, and someone informed me I had posted to the wrong list. This person mentioned that: > OSX has gcc-4.2 or clang 3.1 for 10.8. > > The gcc project has done some cleanups of standard library code, eliminating > some implicit dependencies. So you might need to explicitly include the now > missing headers. > > Yours, > > Jürgen Does anybody have any suggestions for which headers I might be missing? I do not have direct access to the machine with these compile errors, so it's hard for me to just fiddle with my code. thanks for any advice! Amos. 1) gcc.compile.c++ pymodule/bin/gcc-4.4.6/release-core/threading-multi/SingleCalculator_BP.o In file included from pymodule/SingleCalculator_BP.cc:13: ../tools/boost/boost/range/algorithm/equal.hpp: In function ‘void core::wrap_vector(const std::string&) [with T = boost::shared_ptr<core::energy::SingleCalculator>, bool noProxy = true]’: pymodule/SingleCalculator_BP.cc:33: instantiated from here ../tools/boost/boost/range/algorithm/equal.hpp:160: error: ‘boost::range’ is not a function, ../tools/boost/boost/python/iterator.hpp:92: error: conflict with ‘template<class Accessor1, class Accessor2> boost::python::api::object boost::python::range(Accessor1, Accessor2)’ pymodule/wrap_vector.hh:68: error: in call to ‘range’ "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -g -pthread -fPIC -Dcore_MPI -Dkiss_fft_scalar=float -Wno-unknown-pragmas -Wstrict-aliasing=2 -fno-strict-aliasing -DBOOST_PYTHON_MAX_ARITY=30 -DBOOST_SYSTEM_DYN_LINK=1 -I"../tools/boost" -I"../tools/python/include/python2.7" -I"/import/rh_software/openmpi-1.4.3/include" -c -o "pymodule/bin/gcc-4.4.6/release-core/threading-multi/SingleCalculator_BP.o" "pymodule/SingleCalculator_BP.cc" 2) <snip> instantiated from here ../tools/boost/boost/mpi/detail/mpi_datatype_oarchive.hpp:51: error: invalid use of incomplete type ‘struct boost::is_enum<float>’ ../tools/boost/boost/type_traits/is_enum.hpp:181: error: declaration of ‘struct boost::is_enum<float>’ <snip> 3) <snip> ../tools/boost/boost/mpi/detail/mpi_datatype_oarchive.hpp: In member function ‘void boost::mpi::detail::mpi_datatype_oarchive::save_override(const T&, int) [with T = long unsigned int]’: ../tools/boost/boost/mpi/detail/mpi_datatype_oarchive.hpp:51: error: template instantiation depth exceeds maximum of 128 (use -ftemplate-depth-NN to increase the maximum) instantiating ‘struct boost::is_enum<long unsigned int>’ <snip> 4) <snip> instantiated from here ../tools/boost/boost/archive/detail/check.hpp:78: error: ‘value’ is not a member of ‘boost::archive::detail::check_object_versioning() [with T = boost::serialization::nvp<float>]::typex <snip> g++ -v Using built-in specs. Target: x86_64-redhat-linux Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre --enable-libgcj-multifile --enable-java-maintainer-mode --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libjava-multilib --with-ppl --with-cloog --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux Thread model: posix gcc version 4.4.6 20110731 (Red Hat 4.4.6-3) (GCC)

1 0

SVN access problem
by Simon West 20 Nov '12

20 Nov '12

Hi, I am being asked for a username and password when attempting to check out Boost anonymously using the following command: $ svn co http://svn.boost.org/svn/boost/trunk boost-trunk This command was copy-pasted directly from the instructions for anonymous read-only access described at https://svn.boost.org/trac/boost/wiki/BoostSubversion. This is holding up my progress in creating a patch - can anyone help? Thanks, Simon.

1 0

[enable_if] Compile Time Member Overloading
by Christian Henning 20 Nov '12

20 Nov '12

Hi there, can someone tell me why the following doesn't compile with VS2010 SP1? #include <boost/mpl/and.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/utility/enable_if.hpp> using namespace boost; struct foo { void bla() { read_data_24<int, int>(); } template< typename T1 , typename T2 > void read_data_24( typename enable_if< mpl::and_< mpl::true_ , mpl::bool_< is_same< T1, T2 >::type::value > > >::type* /* ptr */ = 0 ) { int i = 9; } }; int main(int argc, char* argv[]) { return 0; } I get the error: 1>gil_test_vc10.cpp(25): error C2039: 'type' : is not a member of 'boost::enable_if<Cond>' 1> with 1> [ 1> Cond=boost::mpl::and_<boost::mpl::true_,boost::mpl::bool_<false>> 1> ] I tried a couple of hours to have make is happen but I don't get it. Thanks, Christian

3 6

[ASIO] "perf" shows overhead of function calls is very high
by Junchang Wang 19 Nov '12

19 Nov '12

Hi list, I'm new to Boost.asio and am solving scaling problems of a Openflow (TCP based) server. We are using one single io_service for packets receiving and transmitting. A thread pool calling io_service::run() processes HTTP requests. A multi-core server is used. I found we can't get benefits from increasing the size of thread pool when it's size is larger than 6. In other words the system doesn't scale any more on more than 6 cores. I checked the program carefully and can make sure there's no lock contention. I profile the program with Linux perf, and it turns out up to 36% of CPU time is wasted in function calls. 36.39% : 0000000000103300 <boost::detail::function::void_function_obj_invoker3<vigil::openflow::v1::construct_and_load<vigil::openflow::v1::ofp_packet_out, vigil:: : BOOST_FUNCTION_TEMPLATE_PARMS : > : struct BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER : { : static BOOST_FUNCTION_VOID_RETURN_TYPE : invoke(function_buffer& function_obj_ptr BOOST_FUNCTION_COMMA 0.02 : 103300: push %rbp 99.66 : 103301: mov %rsp,%rbp 0.00 : 103304: push %r12 0.04 : 103306: mov %rcx,%r12 I printed out the call stack (attached at the tail of this email). It seems for a single packet processing there are more than 30 function calls within Boost. Can that explain why the CPU time on function calls is so high? Are there some ways to avoid this kind of cost? Thanks a lot. --Junchang ================ #0 vigil::openflow::Openflow_datapath::send (this=<optimized out>, msg=0x7ffff567f920) at ../../../../src/coreapps/openflow/openflow-datapath.cc:199 #1 0x00007ffff4c50724 in vigil::openflow::Openflow_datapath::handle_handshake (this=0x7ffff007dd80, e=...) at ../../../../src/coreapps/openflow/openflow-datapath.cc:305 #2 0x00007ffff4c5086a in vigil::openflow::Openflow_datapath::handle_message (this=0x7ffff007dd80, msg=0x7ffff567f920) at ../../../../src/coreapps/openflow/openflow-datapath.cc:228 #3 0x00007ffff4c50a39 in vigil::openflow::Openflow_datapath::recv_cb (this=0x7ffff007dd80, bytes_transferred=<optimized out>) at ../../../../src/coreapps/openflow/openflow-datapath.cc:164 #4 0x00007ffff7bad130 in operator() (a0=<optimized out>, this=0x7ffff007d4b8) at /usr/include/boost/function/function_template.hpp:1013 #5 vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > >::handle_recv ( this=0x7ffff007d480, ec=..., bytes_transferred=<optimized out>) at ../../../src/lib/connection.cc:185 #6 0x00007ffff7bb5fba in call<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > >, boost::system::error_code const, unsigned long const> (b2=@0x7ffff568fa10: 8, b1=..., u=..., this=0x7ffff568f9e0) at /usr/include/boost/bind/mem_fn_template.hpp:271 #7 operator()<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > > (u=..., this=0x7ffff568f9e0, a2=@0x7ffff568fa10: 8, a1=...) at /usr/include/boost/bind/mem_fn_template.hpp:286 #8 operator()<boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, const boost::system::error_code&, const long unsigned int&>, boost::_bi::list2<const boost::system::error_code&, const long unsigned int&> > (a=<synthetic pointer>, f=..., this=0x7ffff568f9f0) at /usr/include/boost/bind/bind.hpp:392 #9 operator()<boost::system::error_code, long unsigned int> (a2=@0x7ffff568fa10: 8, a1=..., this=0x7ffff568f9e0) at /usr/include/boost/bind/bind_template.hpp:102 #10 operator() (this=0x7ffff568f9e0) at /usr/include/boost/asio/detail/bind_handler.hpp:97 #11 asio_handler_invoke<boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long> > ( function=<error reading variable: access outside bounds of object referenced via synthetic pointer>) at /usr/include/boost/asio/handler_invoke_hook.hpp:64 #12 boost_asio_handler_invoke_helpers::invoke<boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long>, boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> > > (function=..., context=...) at /usr/include/boost/asio/detail/handler_invoke_helpers.hpp:39 #13 0x00007ffff7bb637b in asio_handler_invoke<boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long>, boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long> (this_handler=0x7ffff568fbf0, function=...) at /usr/include/boost/asio/detail/bind_handler.hpp:132 #14 invoke<boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long>, boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long> > (context=..., function=...) at /usr/include/boost/asio/detail/handler_invoke_helpers.hpp:39 #15 boost::asio::detail::strand_service::dispatch<boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long> > (this=0x7ffff0001560, impl=@0x7ffff568fbb0: 0x7ffff0047d80, handler=...) at /usr/include/boost/asio/detail/impl/strand_service.hpp:97 #16 0x00007ffff7bb66fa in dispatch<boost::asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> >, boost::system::error_code, unsigned long> > ( handler=<error reading variable: access outside bounds of object referenced via synthetic pointer>, this=0x7ffff568fba8) at /usr/include/boost/asio/strand.hpp:159 #17 operator()<boost::system::error_code, long unsigned int> (arg2=<synthetic pointer>, arg1=..., this=0x7ffff568fba8) at /usr/include/boost/asio/detail/wrapped_handler.hpp:65 #18 operator()<boost::system::error_code, long unsigned int> (arg2=<optimized out>, arg1=..., this=0x7ffff568fba0) at ../../../src/lib/connection.cc:64 #19 operator() (this=0x7ffff568fba0) at /usr/include/boost/asio/detail/bind_handler.hpp:97 #20 asio_handler_invoke<boost::asio::detail::binder2<vigil::custom_alloc_handler<boost::asio::detail::wrapped_handler<boost::asio::io_service::strand, boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> > > >, boost::system::error_code, unsigned long> > (function=<error reading variable: access outside bounds of object referenced via synthetic pointer>) at /usr/include/boost/asio/handler_invoke_hook.hpp:64 #21 invoke<boost::asio::detail::binder2<vigil::custom_alloc_handler<boost::asio::detail::wrapped_handler<boost::asio::io_service::strand, boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> > > >, boost::system::error_code, unsigned long>, vigil::custom_alloc_handler<boost::asio::detail::wrapped_handler<boost::asio::io_service::strand, boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp> > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> > > > > (function=..., context=...) at /usr/include/boost/asio/detail/handler_invoke_helpers.hpp:39 #22 boost::asio::detail::reactive_socket_recv_op<boost::asio::mutable_buffers_1, vigil::custom_alloc_handler<boost::asio::detail::wrapped_handler<boost::asio::io_service::strand, boost::_bi::bind_t<void, boost::_mfi::mf2<void, vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > >, boost::system::error_code const&, unsigned long const&>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<vigil::Stream_connection<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > >, boost::arg<1> (*)(), boost::arg<2> (*)()> > > > >::do_complete (owner=0x6d6b30, base=<optimized out>) at /usr/include/boost/asio/detail/reactive_socket_recv_op.hpp:106 #23 0x0000000000487343 in complete (owner=..., this=0x7ffff007d510) at /usr/include/boost/asio/detail/task_io_service_operation.hpp:35 #24 boost::asio::detail::task_io_service::do_one (this=0x6d6b30, lock=..., this_idle_thread=0x7ffff568fdd0) at /usr/include/boost/asio/detail/impl/task_io_service.ipp:278 #25 0x00000000004874b0 in boost::asio::detail::task_io_service::run (this=0x6d6b30, ec=...) at /usr/include/boost/asio/detail/impl/task_io_service.ipp:130 #26 0x00000000004875c9 in boost::asio::io_service::run (this=0x6d68f8) at /usr/include/boost/asio/impl/io_service.ipp:57 #27 0x00007ffff7971ce9 in thread_proxy () from /usr/lib/libboost_thread.so.1.46.1 #28 0x00007ffff5f2ee9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0 #29 0x00007ffff6237cbd in clone () from /lib/x86_64-linux-gnu/libc.so.6 #30 0x0000000000000000 in ?? ()

2 2

code review please? [boost::asio]
by Littlefield, Tyler 18 Nov '12

18 Nov '12

hello all: I was curious if some boost::asio guru would mind checking this out. I just posted my code in, I'd like to know if there's anything that could be done better. Thanks, //client.h #pragma once #include <queue> #include <boost/asio.hpp> #include <boost/bind.hpp> #include "ClientBuffer.h" class Client { protected: boost::asio::ip::tcp::socket _socket; boost::asio::io_service &_service; std::queue<ClientBuffer*> _buffers; bool _writing; void StartWrite(); void HandleWrite(const boost::system::error_code& error); public: Client(boost::asio::io_service &service); ~Client(); virtual boost::asio::ip::tcp::socket& GetSocket(); virtual void Start() = 0; void Write(const char* data); void Write(void* data, unsigned int size); void Write(const std::string &data); }; //client.cpp #include <boost/asio.hpp> #include <boost/bind.hpp> #include "client.h" #include "ClientBuffer.h" Client::Client(boost::asio::io_service &service): _service(service), _socket(service), _writing(false) { } Client::~Client() { } void Client::StartWrite() { //we don't write if we're already writing. We just content ourselves with having pushed the message to the queue. if (_writing) { return; } //we're writing now. _writing = true; ClientBuffer* buffer = NULL; buffer = _buffers.front(); boost::asio::async_write(_socket, boost::asio::buffer(buffer->GetBuffer(), buffer->GetSize()), boost::bind(&Client::HandleWrite, this, boost::asio::placeholders::error)); } void Client::HandleWrite(const boost::system::error_code& error) { if (_buffers.empty()) { _writing = false; return; } ClientBuffer* buffer = _buffers.front(); _buffers.pop(); if (buffer) delete buffer; if (_buffers.empty()) _writing = false; else StartWrite(); } boost::asio::ip::tcp::socket& Client::GetSocket() { return _socket; } void Client::Write(const char* data) { ClientBuffer* buffer = new ClientBuffer(data); _buffers.push(buffer); StartWrite(); } void Client::Write(void* data, unsigned int size) { ClientBuffer* buffer = new ClientBuffer(data, size); _buffers.push(buffer); StartWrite(); } void Client::Write(const std::string &data) { ClientBuffer* buffer = new ClientBuffer(data); _buffers.push(buffer); StartWrite(); } //TelnetClient.h /* *this client is responsible for handling the telnet protocol. */ #pragma once #include <boost/asio.hpp> #include <boost/bind.hpp> #include "client.h" #include "ClientBuffer.h" class TelnetClient:public Client { int _state; boost::asio::streambuf _buffer; public: virtual void Start(); void Read(); void HandleRead(const boost::system::error_code& error); void HandleCommand(const std::string &line); }; //TelnetClient.cpp #include <string> #include <istream> #include <boost/asio.hpp> #include <boost/bind.hpp> #include "client.h" #include "TelnetClient.h" void TelnetClient::Start() { Write("Welcome to SapphireMud.\n"); Write("Use load <player> <password> to load a character.\n"); Write("Use create <player> <password> to create a new player.\n"); _state = 1; Read(); } void TelnetClient::Read() { boost::asio::async_read_until(_socket, _buffer, '\n', boost::bind(&TelnetClient::HandleRead, this, boost::asio::placeholders::error)); } void TelnetClient::HandleRead(const boost::system::error_code& error) { char buffer[2048]; if (error) { //do something here return; } std::istream input(&_buffer); input.getline(buffer, 2048); HandleCommand(buffer); Read(); } void TelnetClient::HandleCommand(const std::string &line) { Write("I don't understand that!\n"); } -- Take care, Ty http://tds-solutions.net The aspen project: a barebones light-weight mud engine: http://code.google.com/p/aspenmud He that will not reason is a bigot; he that cannot reason is a fool; he that dares not reason is a slave.

2 2

Re: [Boost-users] What is the best idiom for using call_once ?
by John M. Dlugosz 18 Nov '12

18 Nov '12

Date: Sat, 17 Nov 2012 13:51:48 +0100 From: "Vicente J. Botet Escriba" <vicente.botet(a)wanadoo.fr> > Hi, your code suffers from the problem you try to avoid "But we all know this is not > thread safe, at least for the first call" at least in c++98 as you are using static > variables. Actually, my post described the circumstances under which it does in fact work: when VarType has a built-in type that is initialized before program execution, or on C++11 with a constexpr constructor. > here they are some pointers that while not responding exactly to your > question them could help you. > > http://www.justsoftwaresolutions.co.uk/threading/multithreading-in-c++0x-pa… Interesting, the post gets it wrong. A unique_ptr has a constructor (in C++03) so still has the problem. Or, maybe the article is just not clear on how it is to be used: if you must initialize an instance of lazy_init (to the null pointer internally) _before_ multiple threads ask it to be "initialized", that just pushes the problem back to the earlier step. I can see the usefulness though, if you just want to put off the expensive "real" initialization until needed, but can arrange the pre-initialization to be done for-sure earlier. > > http://stackoverflow.com/questions/12302057/c11-safe-double-checked-locking… This points out that under C++11 rules, static locals are thread safe for the first-time initialization. That explains why there is no fancy construct for doing so; it's just there! Nice. Or it will be, some day. I looked at the code generated by Microsoft VS2010 and it does not give this feature, alas. It does tell me though that a compatibility construct like I'm looking for ought to expand into a plain static local for compilers that do work that way; just let the compiler do it. All the more reason to abstract the issue for current uses! —John

1 0

What is the best idiom for using call_once ?
by John M. Dlugosz 17 Nov '12

17 Nov '12

Consider the issue of a static variable inside a function: the idea is to initialize on first use (if any). But we all know this is not thread safe, at least for the first call. Since the C++11 standard library includes a feature just like boost::call_once, that would seem to be the proper way to address this moving forward. And, I don't see anything in the standard that would be more powerful and direct for this purpose, which leaves me to wonder if there is still more that should have been done. But, my question is, what is the "best" or slickest way to use it (for this purpose)? If Lambda functions are available (which is not the case on every platform my code needs to support) _and_ the type of variable in question has some kind of "dead" state available, it's not too bad to write something like this: VarType obtain_singleton() { static boost::once_flag f=BOOST_ONCE_INIT; static VarType retval; boost::call_once (f, [] { retval=the_real_initialization(); }); return retval; } //...later // static VarType val= the_real_initialization; // !!not thread safe on first call!! static VarType val= obtain_singleton(); // do this instead (and write it in another function for conciseness) However, it's more awkward if I can't declare VarType retval to be pre-initialized to some "dead" value, or if it has any constructor at all and would itself re-introduce the thread safety issue! In short, it only works correctly (without the availability of the constexpr feature and types having constructors of such a nature) for primitive types. I've worked around it using a pointer and having the real_init function itself contain a static variable. That makes me think that there should be a simpler way to do it. Or, once the "best way" has been determined, why can't it be done once and succinctly reused? Anyone have one to share?

3 2

Re: [Boost-users] Boost 1.52 .zip bootstrap file -- missing?
by Adam J. Cooper 17 Nov '12

17 Nov '12

I downloaded "boost_1_52_0.zip" from here on 11/16 http://www.boost.org/users/history/version_1_52_0.html I used the native unzip built into Windows 8. There were two folders in the root directory, docs and source files. There was no bootstrap file or any other tools files. - Adam ------------------------------ Message: 2 Date: Sat, 17 Nov 2012 10:13:55 +0000 From: Daniel James <dnljms(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Boost 1.52 .zip bootstrap file -- missing? Message-ID: <CAHOE3yct3am=xamtRZrVGjK+_BjyXESgu9ofMm_F2vyb8435DA(a)mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 On 16 November 2012 23:39, Adam J. Cooper <adam(a)adamcooper.com> wrote: > I download the .zip version of Boost 1.52 > > However, I do not see the bootstrap file when I unzip the contents. That's odd. I just downloaded and there's a 'bootstrap.sh' and 'bootstrap.bat' in the 'boost_1_52_0' directory. Where did you download it from, and what did you use to unzip it? _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users End of Boost-users Digest, Vol 3272, Issue 2 ********************************************

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Boost 1.52 .zip bootstrap file -- missing?
by Adam J. Cooper 17 Nov '12

17 Nov '12

I download the .zip version of Boost 1.52 However, I do not see the bootstrap file when I unzip the contents. Please advise. Thank you, Adam

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(no subject)
by mega deth 16 Nov '12

16 Nov '12

http://mcrtaky.org/wp-content/themes/twentyeleven/hotnews.php?youth293.gif

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