- Boost-users - lists.boost.org

Re: [Boost-users] intrusive_ptr vs shared-ptr
by John M. Dlugosz 23 Jan '13

23 Jan '13

> Well I wouldnt say these items are 'marginal', because most come from real life > scenarios. You can work around things but it is always that u have to remember that > there were some boundary cases with shared_ptr. It took me some time to convince my > colleagues to swap from raw pointers to shared pointers and having some boundary cases > doesn't help then. I still prefer shared pointers, but I am not sure if all in all they > would be better than e.g. intrusive_ptr's with ref counting (even without lacking the > weak_ptr feature). Note that i look upon this from a client perspective (i.e. large data > acquisition application), not from a library builder perspective. I really miss having a "lost and found" feature, which (in the late 90's) I wrote about as being one of the six essential features of my smart pointer design. That is, given a raw pointer p that is already known to the smart pointer system, creating another smart pointer from p will work in harmony with them, NOT break it. I've repeatedly come across code that hooks up objects with other objects in the constructor and I've had to work-around that in various ways, usually by adding a Create wrapper that finishes the work, and sometimes fiddling more than I would have wanted to with the design. I've also found cases where it is really annoying not knowing whether another smart pointer has already been created yet for the object. Anyway, for intrusive smart pointers, the "lost and found" feature is very easy and efficient to implement. So perhaps it should be part of Boost intrusive_ptr as an extension to the standard, or another class can be added with a different feature set. Anyway, if you want a class like that, feel free to grab my old code from the "Classics" or "Repertoire" project parked on github. —John

3 2

[Program Options] terminate parsing after first positional argument
by Stuart Pook 22 Jan '13

22 Jan '13

Hello, How can I tell Boost Program Options to stop parsing the arguments as soon as it finds a positional argument? I'd like to be able to parse the argument list "-v chmod -R -v 600 foo" as having one argument for my program (-v) and the rest as a std::vector of std::string (including the -v). In the attached program I have tried 2 different approaches. The first uses multitoken with the arguments "--command date -u -v", it fails because "-u" isn't known. The second uses collect_unrecognized with "chmod -R -v 600", it doesn't work because -v is interpreted by boost and doesn't end up in the vector. As someone said back in 2005, perhaps I'm trying to write xargs: http://thread.gmane.org/gmane.comp.lib.boost.user/9529/focus=9641 I know that I can ask my users to write a.out -v -- chmod -R -v 600 foo but I don't want to do that. I want them to write "a.out -v chmod -R -v 600 foo". The first positional argument should should tell boost to stop processing. Another slightly different question. If I have a multitoken option that takes doubles how can I get it to accept negative values? If I give my program "--floats 1 8 -4 6" where --floats starts a multitoken option that accepts double, I get an exception saying that "-4" is an unknown option. thanks Stuart This is what my test program gives me with boost 1.50: argv: dd --command date -u -v unrecognised option '-u' Allowed options: -v [ --verbose ] verbose --command arg command to run 2nd try argv: dd chmod -R -v 600 I'm verbose v: chmod -R 600 3rd try argv: dd --floats 1 8 -4 6 unrecognised option '-4' Allowed options: -v [ --verbose ] verbose -f [ --floats ] arg numbers and my program (formatted to fit in 80 characters) #include <boost/program_options.hpp> #include <boost/range/algorithm.hpp> #include <boost/program_options/parsers.hpp> #include <boost/program_options/options_description.hpp> #include <iostream> namespace po = boost::program_options; #define nelements(a) (sizeof (a) / sizeof (a)[0]) void print(char const * * b, char const * * e) { std::cout << "argv: "; std::copy(b, e, std::ostream_iterator<char const *>(std::cout, " ")); std::cout << std::endl; } int main(int argc, char ** argv) { { bool verbose; std::vector<std::string> command; po::options_description desc("Allowed options"); desc.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ("command", po::value<std::vector<std::string> >(&command) ->multitoken(), "command to run") ; char const * args[] = { "dd", "--command", "date", "-u", "-v", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; try { po::store(po::command_line_parser(nelements(args) - 1, args) .options(desc).run(), vm); po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "command: "; boost::copy(command, std::ostream_iterator<std::string>(std::cout, " ")); std::cout << std::endl; } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << desc << "\n"; } } std::cout << "2nd try\n"; { bool verbose; po::options_description desc("Allowed options"); desc.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ; char const * args[] = { "dd", "chmod", "-R", "-v", "600", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; po::parsed_options parsed = po::command_line_parser(nelements(args) - 1, args). options(desc).allow_unregistered().run(); try { po::store(parsed, vm); } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << desc << "\n"; exit(2); } po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "v: "; std::vector<std::string> v = po::collect_unrecognized( parsed.options, po::include_positional); boost::copy(v, std::ostream_iterator<std::string>(std::cout, " ")); std::cout << std::endl; } std::cout << "3rd try\n"; { bool verbose; std::vector<double> f; po::options_description all("Allowed options"); all.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ("floats,f", po::value<std::vector<double> >(&f)->multitoken(), "numbers") ; char const * args[] = { "dd", "--floats", "1", "8", "-4", "6", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; try { po::store(po::command_line_parser(nelements(args) - 1, args) .options(all).run(), vm); po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "floats: "; boost::copy(f, std::ostream_iterator<double>(std::cout, " ")); std::cout << std::endl; } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << all << "\n"; } } }

6 16

boost::program_options - undocumented "*" feature
by ST 21 Jan '13

21 Jan '13

I recently discovered an undocumented feature of `boost::program_options`, namely that it accepts "*" as a special wildcard that allows declaration of a group of options with the same prefix, like this: configOptions.add_options() ("item_*", value<int>(), "items"); This declaration worked as expected and recognized `item_1`, `item_3`, etc, while rejecting unknown options. Well now the question is, how can I write a custom validate function that will populate a map with options key and its value, like this: map<string, int> itemsMap; options_description items("items options"); items.add_options() ("item_*",value<map<string, int>>(&itemsMap)->multitoken(), "items") ; My question is - how do I get the key of the option being validated from within validate() function? template <typename T> void validate(boost::any& v, const std::vector<std::string>& values, map<string, T> *, int) Thank you, Simone

1 0

Support for windows NTLM Authentication Protocol
by Gheorghe Marinca 21 Jan '13

21 Jan '13

Hi, I use asio and need to connect to a proxy server that might require NTLM Authentication Protocol. Is there a way to use this using boost ? Thanks, -Ghita

1 0

Re: [Boost-users] [MultiIndex] more on key extractor issues
by John M. Dlugosz 21 Jan '13

21 Jan '13

On 1/20/2013 11:00 AM, boost-users-request-at-lists.boost.org |Boost/Allow to home| wrote: > From: Joaquin M Lopez Munoz<joaquin(a)tid.es> > Thanks for your elucidation. I'm much more comfortable with the class now. Like most people in this situation, having found the explanation I'm much to busy trying to employ it in real-world projects and don't have time to edit and expand the docs. But, a pointer to your responses on an archiver might be a great quick addition to the documentation page. It occures to me that if the docs were a Wiki then more might get done, including fixing typos and putting this kind of commentary on the Discussion page. —John

1 0

[MSM] Get state name as string
by Stefan Wiehler 20 Jan '13

20 Jan '13

Hello, For debugging purposes, I want to get the current state name as a string. For this purpose I found the class get_state_name in the tools section of the backend. Unfortunately there is no example on how to use this method in the documentation nor anywhere else; and the extensive use of templates makes it very difficult for me to infer this. I am especially confused about the argument boost::msm::wrap<StateType> const& of the call operator. What do I have to provide her? Could anybody please post a short example how to this? Kind regards, Stefan Wiehler

2 1

Re: [Boost-users] [MultiIndex] more on key extractor issues
by John M. Dlugosz 20 Jan '13

20 Jan '13

> Have you taken a look at the table in: > > http://www.boost.org/libs/multi_index/doc/tutorial/ > key_extraction.html#advanced_key_extractors > > Regardless of whether the indexed-by member is const or not, when using > pointers to const elements the proper way of declaring the extractors is: > > > member< > ItemBase, > const unsigned long, > &ItemBase::some_member > > > > member< > ItemBase, > const S2, > &ItemBase::another_member > > > > This should clear problems away both in VS and Clang (please report > otherwise.) > > Joaqu?n M L?pez Mu?oz > Telef?nica Digital > > I read that part in detail (including the typo, T:gg instead of T::gg), going over all the MI docs again after my postings. I agree this seems to address that use-case, but I really don't understand the table and section, and certainly had no clue what it was getting at when I read it without this issue specifically in mind. "The column "applicable to |const| elements?" states whether the corresponding key extractor can be used when passed constant elements (this relates to the elements specified in the first column, not the referenced |T| objects)." What does that mean? I was actually looking at this in regards to figuring out what a non-const member function extractor was good for. "this also implies that |multi_index_container|s of elements of |T| cannot be sorted by |T::g| or |T::gg|," if you are not using it to sort by, what is the point of having the key extractor? Anyway, I found that it works correctly on both compilers if the middle argument (the key type) is declared const for member and not for const_mem_fun. I suppose that is due to differences in the metaprogramming, but really they should be treated the same. Const on the first parameter, T, doesn't seem to matter if it's declared const or not. ---John

2 1

Re: [Boost-users] [MultiIndex] is ordered_non_unique stable?
by John M. Dlugosz 20 Jan '13

20 Jan '13

> The only problem with this is that the behavior is *undocmented*. If you want > to stay legal, use hinted insertion with end() (which will *documentedly* > work for all the ordered_non_unique indices of your container, not only the one > you happen to be doing for the insertion.) > > Joaqu?n M L?pez Mu?oz > Telef?nica Digital > > > That is very interesting. The wording is kind of strange though: "If succesful, insertion happens as close as possible to the location just prior to |position|." I wonder if stability was the intention? Thank you very much for your analysis of the code. ---John

2 1

Help a novice today getting started with regex.hpp
by Neil Sutton 20 Jan '13

20 Jan '13

Please can someone tell me the best place to start studying how to write and use boost::regex.hpp? Is there any documentation or tutorial that is easier for a novice to understand than the standard distribution documentation?

4 3

[Container] --begin() on empty deque crashes
by TONGARI 20 Jan '13

20 Jan '13

Hi there, The code below would simply crash on g++ 4.7.1/MinGW with default optimization level, it doesn't shown with -O/1/2/3 ---------------------------------------- boost::container::deque<int> d; --d.begin(); ---------------------------------------- I took a look into the impl, seems that it dereferences from (this->m_node - 1) which is invalid at the time. I guess it's the problem. Thoughts?

3 5