June 2008 - Boost - lists.boost.org

bad include guards
by Steven Watanabe 26 Jan '17

26 Jan '17

AMDG The following pairs of files have identical include guards ./boost/concept_check/general.hpp ./boost/concept/detail/msvc.hpp ./boost/concept_check/msvc.hpp ./boost/concept/detail/msvc.hpp ./boost/filesystem/cerrno.hpp ./boost/cerrno.hpp ./boost/interprocess/containers/tree.hpp ./boost/interprocess/containers/detail/tree.hpp ./boost/mpl/min_max.hpp ./boost/mpl/max.hpp ./boost/mpl/vector/aux_/front.hpp ./boost/mpl/list/aux_/front.hpp ./boost/multi_index/identity_fwd.hpp ./boost/multi_index/identity.hpp ./boost/python/pointee.hpp ./boost/python/detail/pointee.hpp ./boost/spirit/phoenix/closures.hpp ./boost/lambda/closures.hpp ./boost/xpressive/proto/v1_/proto_typeof.hpp ./boost/xpressive/proto/proto_typeof.hpp ./libs/config/test/boost_no_dep_nested_class.ipp ./libs/config/test/boost_has_vc6_mem_templ.ipp ./libs/config/test/boost_no_mem_templates.ipp ./libs/config/test/boost_has_vc6_mem_templ.ipp ./libs/config/test/boost_no_std_allocator.ipp ./libs/config/test/boost_has_vc6_mem_templ.ipp ./libs/conversion/test.hpp ./libs/any/test.hpp ./libs/interprocess/example/print_container.hpp ./libs/interprocess/example/printcontainer.hpp ./libs/interprocess/test/expand_bwd_test_template.hpp ./libs/interprocess/test/allocation_test_template.hpp ./libs/interprocess/test/printcontainer.hpp ./libs/interprocess/example/printcontainer.hpp ./libs/interprocess/test/print_container.hpp ./libs/interprocess/example/printcontainer.hpp ./libs/iostreams/test/detail/utf8_codecvt_facet.hpp ./boost/detail/utf8_codecvt_facet.hpp ./libs/regex/test/regress/test_regex_search.hpp ./libs/regex/test/regress/test_partial_match.hpp ./libs/serialization/test/C.hpp ./libs/serialization/test/A.hpp ./libs/xpressive/perf/regex_comparison.hpp ./libs/regex/performance/regex_comparison.hpp ./tools/inspect/time_string.hpp ./tools/common/time_string.hpp In Christ, Steven Watanabe

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Why no non-null smart pointers?
by Ross MacGregor 29 Apr '14

29 Apr '14

I just created a very small smart pointer libary for our project. It will contain two types of shared pointers: SharedHandle and NullableSharedHandle. SharedHandle will be a shared pointer that cannot be null by ensuring a non-null construction while NullableSharedHandle will basically be a typedef for boost::shared_ptr. I firmly believe that code can be made more reliable by minimizing the use of nullable pointers. To this end, I think it is important that we start using non-null pointer types. Ideally the compiler would be able to understand a non-null pointer and catch bugs at compile time, but I think we can still improve things with a few runtime checks. If we make sure that a shared pointer is constructed with a non-null pointer and ban any reset() type methods, we guarentee that it points to something. This can be beneficial for the following reasons: 1. Any function that uses this type will no longer be burdened with precondition checks to make sure variables of this type are not null. 2. It's type is simply more explicit and better explains its function. 3. Moving the non-null check to the creation phase will reduce the possibility of encountering null pointer exceptions at runtime (assuming there are many more pointer references than constructor calls). So my little pointer library seems to make a lot of sense, but if so why hasn't this simple smart pointer variation made it into boost yet? Has this been discussed somewhere already? My search on non-null smart pointers is not revealing much discussion on the topic. Regards, Ross

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[asio] read_until -- possibly misleading documentation?
by Richard Smith 15 Apr '10

15 Apr '10

The documentation for Boost.ASIO (which is otherwise very comprehensive) says of the boost::asio::read_until set of overloads: | Read data into a streambuf until a delimiter is | encountered. <http://www.boost.org/doc/libs/1_35_0/doc/html/boost_asio/reference/read_unt…> What the function actually does is to read blocks of data into the streambuf, and stop when the delimiter is found. This means that frequently data beyond the delimiter will be read into the streambuf. (And this is elaborated in more detail on the individual function's pages, if a reader looks there.) I appreciate that this behaviour is compatible with the documentation, but someone less familiar with ASIO could easily assume that the function will read as far as the delimiter and no further. (And I have just spent a fair amount of time debugging a piece of code where the author had made this assumption.) Could we change the summary documentation to read something like: | Read data into a streambuf at least until a delimiter is | encountered. The implementation may read beyond the | delimiter, but will not block when doing so. While I'm on the subject of ASIO documentation, I can't see any documentation on whether the service_name parameters to the basic_resolver_query constructors are allowed to be port numbers (e.g. "80") or whether they have to be symbolic names (e.g. "http"). Port numbers work, at least on Linux, but it's not clear whether this is something that I should be relying on. Similarly for IPv4 and IPv6 addresses in the host_name parameter. Richard Smith

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Proposed addition to the iterator library for iterating over all tuples.
by Alex Mendes da Costa 19 Jun '09

19 Jun '09

Hi folks: I quite often have to write code to do the following: Given N sequences, generate all the N-tuples s.t. the i'th element in each tuple is drawn from the i'th sequence. For example, if sequence S1 is { 1, 2, 3 } and sequence S2 is { 10, 20 }, I need to generate these tuples: (1, 10), (2, 10), (1, 20), (2, 20). I think this problem could be solved elegantly with a iterator similar to zip_iterator. I have some questions: (1) Is there already a way to do this in boost? (2) If not, would this be a worthwhile addition to the iterator library? (3) If so, could I contribute code for this, or must the existing library owners write it? (4) If so, how would I go about getting my code added? Most of the docs seem to be about submitting entire libraries, rather than extensions to existing libraries. Thanks, Alex

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[mpl] is there a or_seq like logical metafunction?
by vicente.botet 17 Jun '09

17 Jun '09

Hello, I needs calculate the mlp::or_ of a sequence of nullary logical metafunction. This seams quite simple. I have do the following: <code> template <typename Seq> struct or_seq; template <typename Seq, long N> struct or_seq_aux : mpl::or_< typename mpl::front<Seq>::type, or_seq<typename mpl::pop_front<Seq>::type> > {}; template <typename Seq> struct or_seq_aux<Seq, 1> : mpl::front<Seq>::type {}; template <typename Seq> struct or_seq : or_seq_aux<Seq, mpl::size<Seq>::value> {}; </code> Is there a boost or_seq like logical metafunction? Is there a better way to do it? I would be extremely interested in any suggestions. Best regards --------------------------- Vicente Juan Botet Escriba

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Proposed templated integer_sort
by Steven Ross 25 Apr '09

25 Apr '09

Would there be interest in an integer_sort call that is faster than std::sort? Spreadsort is an in-place hybrid radix-based and comparison-based algorithm with better worst-case and average-case (roughly 20-50%) performance than introsort on random integer data. The worst-case advantage is algorithmic, with Spreadsort taking the better of O(n(square_root(bit_sizeof(data) - log(n)))) and O(nlog(n)) time. For 32-bit integers, that's O(n(square_root(32 - log(n)))), so for a log(n) of 16 (65536 items), it's 4n (plus a small constant times n), vs 16n for introsort. For larger n, the advantage vs. pure comparison-based algorithms increases. In effect, Spreadsort smoothly transitions from pure MSB Radix sort to std::sort with its data cut up by a couple iterations of MSB Radix sort (reducing the size of the log(n) factor), depending upon the distribution and size of the data. I could write a templated version of Spreadsort for the Boost library if there is interest. It would work for anything that supports the << and - operators. It could also handle standard floats sorted as integers. Functors supporting << and - could make it more general. Multi-dimensional sorting is also sped up by Spreadsort. I could also write a similar string_sort, that should also be significantly faster than std::sort. This would look much like postal sort, just using introsort after a certain number of iterations. Is this of interest? http://sourceforge.net/projects/spreadsort

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Profiling template instantiations
by Steven Watanabe 12 Feb '09

12 Feb '09

AMDG Over the last few days, I've been working on a tool that counts the number of class template instantiations in a translation unit. To use it from a jamfile import profile_templates : : directory of the tool ; template-profile result : some_file.cpp : <include>some_directories ; If everything works, this will create a file with the extension .tp which will contain the number of times each class template was instantiated, with the most common templates at the top. I've put a zip of a rough version in the vault. http://www.boost-consulting.com/vault/index.php?action=downloadfile&filenam… Caveats: I've only tested with Visual C++ 9.0 and gcc 3.4.4 on cygwin so far. Other compilers won't work, yet. Other versions of these compilers may or may not work. It may be necessary to add link=static to the bjam command line. In Christ, Steven Watanabe

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Re: [boost] Profiling template instantiations (Steven Watanabe)
by PORKOLAB Zoltan 12 Feb '09

12 Feb '09

Hi Steven, We have created a framework for debugging/profiling template metaprograms in 2006. It might give you a few tips. It works based on the same idea you have. We instrument all template codes, both at the begining and at the end of each template we insert a special piece of code emitting warning messages of a well-defined form. Before instrumentation we create an XML file to remember the template positions in the source file. When we parse the warning, using this information we can reconstruct the instantiation stack knowing the original line numbers, identifiers, etc.. At the end we produce another XML for possible front-ends. The framework uses boost::spirit and boost::wave. We have also implemented and tested a visual studio plug-in. An overview of the whole idea: http://gsd.web.elte.hu/templight/ There is also a GPCE article about the framework, you can find it here: http://portal.acm.org/citation.cfm?id=1173746&coll=portal&dl=ACM&CFID=47731… or here: http://gsd.web.elte.hu/contents/articles/gpce06.pdf You can download both the VS binaries and the source from: http://people.inf.elte.hu/pocok Please feel free to use the code or any of the ideas. For technical question you can find Jozsef: jmihalicza(a)gmail.com or me. Regards, Zoltan

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[thread/interprocess] could we improve recursive_mutex constructor
by vicente.botet 24 Jan '09

24 Jan '09

Hi, the recursive_mutex constructor initialize/set/destroy the pthread_mutexattr_t every time. I'm wondering if we can improve the efficiency storing this on a static variable which will be initialized once. What could be the better way to initialize this static variable? Note: the same applies to interprocess mutexes. recursive_mutex() { // begin code that can be initialized only once pthread_mutexattr_t attr; int const init_attr_res=pthread_mutexattr_init(&attr); if(init_attr_res) { throw thread_resource_error(); } int const set_attr_res=pthread_mutexattr_settype(&attr,PTHREAD_MUTEX_RECURSIVE); if(set_attr_res) { throw thread_resource_error(); } // end code that can be initialized only once int const res=pthread_mutex_init(&m,&attr); if(res) { throw thread_resource_error(); } // begin code that can be removed BOOST_VERIFY(!pthread_mutexattr_destroy(&attr)); // end code that can be removed } Regards, Vicente

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manipulators for filtering_stream s
by Roland Schwarz 22 Jan '09

22 Jan '09

Surprisingly I was not able to find on the net code that would give me a smart way to indent a stream. So I wrote a little filter based on the boost iostreams library. My first attempt was: boost::iostreams::filtering_ostream out; indent_filter ind(4); out.push(ind); out.push(std::cout); However trying to control it via e.g. ind.in() ind.out() turns out to be problematic interface since, 1) out.push() takes a copy of ind 2) the interface ind.in() is suboptimal. With my attached example it is possible to: #include "indent.hpp" ... boost::iostreams::filtering_ostream out; indent_filter::push(out,2); out.push(std::cout); ... And use it like so: out << "Hello Filter!\n" << indent_in << "this is\n" << "indented\n" << indent_out << "until here\n" ; Which will result in output: Hello Filter! this is indented until here The state is stored in the ios base class of the stream, by way of the pword mechanism. Consequently the filter stream even may be downcast to a basic_ostream, and the indenter will still work. E.g. with out defined as above: ... foo(out); ... void foo(std::ostream& out) { out << indent_in << "out is a downcast filter_stream\n" << indent_out << "end of indentation\n" ; } If you want to try it out, you just need to include the header indent.hpp. If someone thinks the snippet is usable either as an example for the iostreams library or the filter streams manipulator idea is worth generalizing to make it usable for other filters too, I would be glad to hear from you. -- _________________________________________ _ _ | Roland Schwarz |_)(_ | aka. speedsnail | \__) | mailto:roland.schwarz@chello.at ________| http://www.blackspace.at

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