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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

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What is the best idiom for using call_once ?
by John M. Dlugosz 18 Nov '12

18 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?

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Re: [Boost-users] Boost 1.52 .zip bootstrap file -- missing?
by Adam J. Cooper 18 Nov '12

18 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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Updated serialization performance tests
by Brian Wood 16 Nov '12

16 Nov '12

Shalom I've updated this page -- http://webEbenezer.net/comparison.html with results from Boost 1.52. A few notes about the testing: I decided to use -O2 on the Linux/g++ tests. In previous tests I used -O3. I hadn't updated the Windows test results since the Boost 1.48 time-frame. Around Boost 1.51 I had to start building the serialization library in Boost with runtime-link=static in order to get the Windows tests to build. I haven't understood why that became necessary, but the results for the serialization library in Boost seem to have been adversely affected by this. On Windows, I now report that tests built with the serialization library in Boost are over 1.8 times slower than parallel Ebenezer tests. Previously I reported the tests built with the serialization library in Boost were between 1.7 and 1.8 times slower than the Ebenezer tests. -- Brian Ebenezer Enterprises -- making programming fun again. http://webEbenezer.net

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how to build a release version of my application from source control using boost libs?
by Anil 16 Nov '12

16 Nov '12

Trying to build a release version from source code put into Clearcase source control. Boost is installed on my computer hard disk. what libraries should I copy to the repository? I tried copying libboost_regex-vc90-mt-gd-1_51.lib but it still gave an error. 1>------ Build started: Project: MyApplication, Configuration: Release Win32 ------ 1>Compiling... 1>MyApplication.cpp 1>.\MyApplication.cpp(40) : warning C4627: '#include <boost/property_tree/ptree.hpp>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(41) : warning C4627: '#include <boost/property_tree/xml_parser.hpp>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(42) : warning C4627: '#include <boost/foreach.hpp>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(43) : warning C4627: '#include <boost/lexical_cast.hpp>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(44) : warning C4627: '#include <string>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(45) : warning C4627: '#include <set>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(46) : warning C4627: '#include <exception>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(47) : warning C4627: '#include <iostream>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(48) : warning C4627: '#include <fstream>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(49) : warning C4627: '#include "MyApplication.h"': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(50) : warning C4627: '#include <boost/filesystem.hpp>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(51) : warning C4627: '#include <boost/regex.hpp>': skipped when looking for precompiled header use 1> Add directive to 'stdafx.h' or rebuild precompiled header 1>.\MyApplication.cpp(875) : fatal error C1010: unexpected end of file while looking for precompiled header. Did you forget to add '#include "stdafx.h"' to your source? 1>Build log was saved at "file://a:\MyApplication\Release\BuildLog.htm" 1>MyApplication - 1 error(s), 12 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== how to build a release version of my application from source control using boost libs?

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Newbie-Question: recursive_directory_iterator and Unicode
by Andy 16 Nov '12

16 Nov '12

Hi all, i'm using the following code-part to show a file-listing of the current directory: boost::locale::generator gen; std::locale l = gen(""); std::locale::global(l); boost::filesystem::recursive_directory_iterator it(L"."); boost::filesystem::recursive_directory_iterator itEnd; while (it != itEnd) { if (boost::filesystem::status_known(it->status()) && boost::filesystem::is_regular(it->status())) { cout << it->path() << endl; } ++it; } This work's great but not if some files contain unicode-characters. If so, then a lot of ????'s will be printed. Could anyone show me how to print those unicode-characters to stdout? Using wcout won't print anything. I'm new to boost and unicode and i'm not sure if this is a problem of boost! I'm using MinGW (gcc (tdm-1) 4.6.1), Boost 1-52, ICU 50.1 - Output goes to the windows command-prompt (Already tried "chcp 65001") Thanks, Andreas

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Build boost 1.52 on Mac OS X 10.8.2 with Clang c++11
by Kikohs x 15 Nov '12

15 Nov '12

Hello, I cannot compile boost with clang 3.1 on Mac os x 10.8.2. This is what I did: ./boostrap.sh --with-toolset=clang ./b2 toolset=clang cxxflags="-std=c++11 -stdlib=libc++" linkflags="-stdlib=libc++" I also tried without chrono, test, wave and signals. I tried a user-config.jam with using clang-darwin This is the error I have for almost every file: /boost/config/select_stdlib_config.hpp:18:12: fatal error: 'cstddef' file not found It is kind of similar to [ http://stackoverflow.com/questions/8486077/how-to-compile-link-boost-with-c… ] I do have the latest Xcode 4.5.2 with the command line tools installed. Here is part of the console output: Kikohs:trunk kikohs$ ./b2 toolset=clang cxxflags="-std=c++11 -stdlib=libc++" linkflags="-stdlib=libc++" Performing configuration checks - 32-bit : no - 64-bit : yes - x86 : yes - has_icu builds : no warning: Graph library does not contain MPI-based parallel components. note: to enable them, add "using mpi ;" to your user-config.jam - gcc visibility : yes - long double support : no warning: skipping optional Message Passing Interface (MPI) library. note: to enable MPI support, add "using mpi ;" to user-config.jam. note: to suppress this message, pass "--without-mpi" to bjam. note: otherwise, you can safely ignore this message. Building the Boost C++ Libraries. - iconv (libc) : no - iconv (separate) : yes - icu : no - icu (lib64) : no Component configuration: - atomic : building - chrono : building - context : building - date_time : building - exception : building - filesystem : building - graph : building - graph_parallel : building - iostreams : building - locale : building - math : building - mpi : building - program_options : building - python : building - random : building - regex : building - serialization : building - signals : building - system : building - test : building - thread : building - timer : building - wave : building ...patience... ...patience... ...patience... ...patience... ...found 8672 targets... ...updating 1127 targets... common.mkdir bin.v2/libs/atomic common.mkdir bin.v2/libs/atomic/build common.mkdir bin.v2/libs/atomic/build/clang-darwin-4.2.1 common.mkdir bin.v2/libs/atomic/build/clang-darwin-4.2.1/debug clang-darwin.compile.c++ bin.v2/libs/atomic/build/clang-darwin-4.2.1/debug/lockpool.o In file included from libs/atomic/src/lockpool.cpp:1: ./boost/atomic.hpp:10:10: fatal error: 'cstddef' file not found #include <cstddef> ^ 1 error generated. "clang++" -x c++ -O0 -g -std=c++11 -stdlib=libc++ -O0 -fno-inline -Wall -g -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_DYN_LINK=1 -DBOOST_ATOMIC_SOURCE -I"." -c -o "bin.v2/libs/atomic/build/clang-darwin-4.2.1/debug/lockpool.o" "libs/atomic/src/lockpool.cpp" Any help would be greatly appreciated, Thank you, Kikohs

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A Special Note for Boost 1.52.0 and Higher - how this affects me?
by Adam Romanek 15 Nov '12

15 Nov '12

Hi, I've just read the Special Note for Boost 1.52.0 and Higher. I must say that I don't fully understand what's going on and how this affects me. I'm using some of Boost's libraries with gcc on Ubuntu. Most often it's gcc 4.4.3, sometimes 4.6.3 but without C++0x mode. Does the change in boost::result_of affect me in any way? Can it make my code fail to compile or make it behave in a different way than before? I just don't understand whether a switch from Boost 1.51.0 to 1.52.0 may do any harm to my code. WBR, Adam Romanek

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