November 2012 - Boost - lists.boost.org

Heads up - string_ref landing
by Marshall Clow 12 Dec '12

12 Dec '12

I'm about to check in some new functionality into the string_algo library; an implementation of string_ref. A string_ref is a non-owning reference to a string. It is implemented as a {pointer, length} pair, and is exceedingly useful when parsing, and manipulating strings in "read-only" ways. The header will be in boost/algorithm/string_ref.hpp, but I welcome discussion about where it should live. Ideally, I think it should be just "boost/string_ref.hpp". Basic sanity tests will be checked in with the header file - I have tested on clang, clang11, and gcc. One reason for checking this in now is to get the tests run on lots of different systems. Docs will be coming soon, but http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3442.html is the proposal for "a future version of C++" ;-) Please let me know what you think! -- Marshall Marshall Clow Idio Software <mailto:mclow.lists@gmail.com> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki

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Using c++11 features in clang
by Marshall Clow 11 Dec '12

11 Dec '12

In response to a some questions on the boost-users list (and boost bug reports), I wrote up this: http://marshall.calepin.co/llvmclang-and-standard-libraries-on-mac-os-x.html I don't know if this should be a FAQ entry for Boost, or for clang. Suggestions/comments/edits welcome. -- Marshall Marshall Clow Idio Software <mailto:mclow.lists@gmail.com> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki

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[algorithm][hex] function hex_char_to_int in unnamed namespace in header file
by Felipe Magno de Almeida 10 Dec '12

10 Dec '12

Hello, AFAIK, unnamed namespaces are dangerous in headers. There is a commentary just above the function definition: // this needs to be in an un-named namespace because it is not a template // and might get included in several compilation units. This could cause // multiple definition errors at link time. But it seems the better thing would be to define it inline. It is exactly because it can be used in several translation units that it can cause an ODR violation if defined in a unnamed namespace AFAIK. Regards, -- Felipe Magno de Almeida

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Boost.Test updates in trunk: need for (mini) review?
by Gennadiy Rozenal 09 Dec '12

09 Dec '12

Hi, It's been a long while since I merged any changes into boost release and by now there are whole bunch of new features there. Some are small, but some others are big ones such that they can change the way people use the library. I'd like to list them here (excluding bug fixes and removal of deprecated interfaces) and ask what should we do with these. Specifically let me know if you think these require some kind of (mini) review from community, but any other comments are welcome as well. So here we go: I. New testing tool BOOST_CHECKA This tool is based on excellent idea from Kevlin Henney. I chose the name CHECKA for this tool due to the lack of better name, but I am open to suggestions. This testing tool capable of replacing whole bunch of existing other tools like BOOST_CHECK_EQUAL, BOOST_CHECK_GT etc. Usage is the most natural you can wish for: BOOST_CHECKA( var1 - var2 >= 12 ); And the output will include as much information as we can get: error: in "foo": check var1 - var2 >= 12 failed [23-15<12] II. New "data driven test case" subsystem New data driven test case subsystem represent a generalization of parameterized test case and test case template and eventually will replace both. The idea is to allow user to specify an arbitrary (monomorphic or polymorphic) set of samples and run a test case on each of the samples. Samples can have different arity, thus you can have test cases with multiple parameters of different types. For now we support following dataset kinds (aside of generators none of dataset constructions routines performs *any* copying): a) singleton - dataset constructed out of single sample data::make(10) - singleton dataset with integer sample data::make("qwerty") - singleton dataset with string sample b) array - dataset constructed out of C array int a[] = {1,2,3,4,5,6}; data::make(a) - dataset with 6 integer values c) collection - dataset constructed out of C++ forward iterable collection std::vector<double> v{1.2, 2.3, 3.4, 5.6 }; data::make(v) - dataset with 6 double values d) join - dataset constructed by joining 2 datasets of the same type int a[] = {1,2,3}; int b[] = {7,8,9}; data::make(a) + data::make(b) - dataset with 6 integer values e) zip - dataset constructed by zipping 2 datasets of the same size, but not necessarily the same type This dataset has an arity which is sum of argument dataset arities. int a[] = {1,2,3}; char* b[] = {"qwe", "asd", "zxc"}; data::make(a) ^ data::make(b) dataset with 3 samples which are pairs of int and char*. f) grid - dataset constructed by "multiplying" 2 datasets of the same different sizes and types type This dataset has an arity which is sum of argument dataset arities. int a[] = {1,2,3}; char* b[] = {"qwe", "asd"}; double c[] = {1.1, 2.2}; data::make(a) * data::make(b) * data::make(c) dataset with 12 samples which are tuples of int and char* and double. g) xrange generator dataset which produes samples in some range data::xrange( 0., 3., 0.4 ) - dataset with 8 double samples data::xrange<int>((data::begin=9, data::end=15)) - dataset with 6 int samples data::xrange( 1., 7.5 ) - dataset with 7 double samples data::xrange( 5, 0, -1 ) - dataset with 5 int samples h) random - generator dataset with unlimited number of random samples data::random(data::distribution = std::normal_distribution<>(5.,2)) dataset with random double numbers following specified distribution data::random(( data::engine = std::minstd_rand(), data::distribution = std::discrete_distribution<>(), data::seed = 20UL )); dataset with random int numbers following specified distribution While all this interfaces can be used by itself to build complex datasets with various purposes, primary use case it was developped for is new data driven test case interface: BOOST_DATA_TEST_CASE( test_name, dataset, parameter_names... ) Here are couple examples: int samples1[] = {1,2,3}; BOOST_DATA_TEST_CASE( t1, samples1, sample ) { BOOST_CHECKA( foo(sample) > 0 ); } Above test case is going to be executed 3 times with different sample values char* strs[] = {"qwe", "asd", "zxc", "mkl" }; BOOST_DATA_TEST_CASE( t1, data::xrange(4) ^ strs ^ data::random(), intval, str, dblval ) { MyObj obj( dblval, str ); BOOST_CHECKA( obj.goo() == intval ); } Above test case will be executed 4 times with different values of parameters intval, str, and dblval. Polymorphic datasets are still being developed, but should appear soon(ish). III. Auto-registered test unit decorators. Previously is was not possible and/or convenient to assign attributes to the automatically registered test units. To alleviate this I've introduced a notion of test unit decorator. These can be "attached" to any test unit similarly to like it is done in other languages Following decorators already implemented: label - adds labels to a test unit expected_failures - set expected failures for a test unit timeout - sets timeout for a test unit description - sets a test unit description depends_on - sets a test unit dependency enable_if/disable_if - facilitates a test unit status change fixture - assigns fixture to a test units Test unit description is new test unit attribute, which is reported by new list_content command line argument described below. Usage of labels covered below as well. enable_if/disable_if allow new, much more flexible test management. By adding enable_if/disable_if decorators to the test unit you can conditionally select which test units to run at construction time based on some compile time or run-time parameters. And we finally we have suite level fixtures which are set by attaching fixture decorator to a test suite (suite level fixtures executed once per test suite). Attachment of decorator is facilitated by using of BOOST_TEST_DECORATOR. Note that you can use any of '+', '-', '*' symbols to attach decorator (and any number of '*'): BOOST_TEST_DECORATOR( + unittest::fixture<suite_fixture>() ) BOOST_AUTO_TEST_SUITE( my_suite1 ) { } BOOST_TEST_DECORATOR( - unittest::timeout( 100 ) - unittest::expected_failures( 1 ) - unittest::enable_if( 100 < 50 ) ) BOOST_AUTO_TEST_CASE( my_test5 ) BOOST_TEST_DECORATOR( **** unittest::label( "L3" ) **** unittest::description( "suite description" ) **** unittest::depends_on( "my_suite2/my_test7" ) ) BOOST_AUTO_TEST_CASE( my_test11 ) IV Support for "run by label" plus more improvements for filtered runs Previously you only had an ability to filter test unit to execute by name. Now you can attach labels to test units and create collections to run which are located in arbitrary positions in test tree. For example you can have special label for performance test cases, which is attached to all test units which are responsible for testing performance of your various components. Or you might want to collect exception safety tests etc. To filter test units by level you still use --run_test CLA. Labels are dented by @prefix: test.exe --run=@performance You can now repeat --run_test argument to specify multiple conditions: test.exe --run=@performance,@exception_safety --run=prod/subsystem2 In addition run by name/label now recognizes dependencies. So if test unit A depends on test unit B and test unit B is disabled/is not part of current run test unit A will not run as well. Finally you now have an ability to specify "negative" conditions, by prefixing name or label with ! test.exe --run=!@performance This will run all test units which are not labeled with "performance". V. Support for failure context In many scenarios it is desirable to specify an additional information to a failure, but you do not need to see it if run is successful. Thus using regular print statements is undesirable. This becomes especially important when you develop common routine, which performs your testing and invoke it from multiple test units. In this case failure location is no help at all. To alleviate this problem two new tools are introduced: BOOST_TEST_INFO BOOST_TEST_CONTEXT BOOST_TEST_INFO attaches context to next assertion which is executed. For example: BOOST_TEST_INFO( "a=" << a ); BOOST_CHECKA( foo(a) == 0 ); BOOST_CHECK_CONTEXT attaches context to all assertions within a scope: BOOST_CHECK_CONTEXT( "Starting test foo from subset " << ss ) { BOOST_CHECKA( foo(ss, a) == 1 ); BOOST_CHECKA( foo(ss, b) == 2 ); } VI. Two new command line arguments: list_context, wait_for_debugger Using list_context you can see a full or partial test tree of your test module. wait_for_debugger allows to force test module to wait till you attach debugger. VII. Colored output. Using new CLA --color_output you can turn on colored output for error and information messages VIII New production testing tools interface introduced This feature was covered in details in my presentation in BoostCon 2010. The gist if this is an ability to use Boost.Test testing tools interfaces in production (nothing to do with testing) code. User supplied implementation is plugged in IX. Number of smaller improvements: * Notion of framework shutdown. Allows to eliminate some fake memory leaks * Added checkpoints at fixture entry points, test case entry point and test case exit point for auto registered test cases * New FPE portable interfaces introduced and FPE handling is separated from system errors handling. You can detect FPE even if catch_system_error is false * Added an ability to erase registered exception translator * execution_monitor: new interface vexecute - to be used to monitor nullary functions with no result values * test_tree_visitor interface extended to facilitate visitors applying the same action to all test units * execution_monitor use typeid to report "real" exception type if possible. * New ability to redirect leaks report into a file Thank you for your time, Gennadiy

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[config] Macro for null pointer
by Edward Diener 08 Dec '12

08 Dec '12

I have found something like this to be helpful, when working with multiple compilers: #include <boost/config.hpp> #if defined(BOOST_NO_NULLPTR) #define BOOST_XXX_NULLPTR 0 #else #define BOOST_XXX_NULLPTR nullptr #endif where XXX is some local name for my own use. And then use BOOST_XXX_NULLPTR in places where a null pointer is needed. Would this be a candidate for a BOOST_NULLPTR macro in the config library instead ? Edward Diener

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[iterator] UB when implicitly using default constructed counting_iterator<unsigned>
by Peter Sommerlad 07 Dec '12

07 Dec '12

Hi Jeffrey, hi all, I believe the usability of counting iterator could be improved, by value-initializing its Iterator type in the default constructor, because integral types won't be initialized by its default constructor. This can lead to hard to recognize user errors, e.g., when wrapping such a counting iterator with a filter iterator. counting_iterator is special in that sense, because to my understanding it is intended to adapt integral types to become iterators. And a default initialized scalar type, isn't. I suggest a one line change: counting_iterator() { } should become counting_iterator() : super_t(Incrementable()) { } The following example program shows the interesting UB, because the 3rd argument of make_filter_iterator, default constructs a counting_iterator<unsigned>(). Any thoughts? Objections? Teachings... Regards Peter. =====>8 #include <iostream> #include <boost/iterator/filter_iterator.hpp> #include <boost/iterator/counting_iterator.hpp> #include <algorithm> #include <iterator> #include <functional> struct is_prime{ bool operator()(unsigned int val) const { if (val < 2) return false; using std::placeholders::_1; auto ce=boost::make_counting_iterator(val); return ce==std::find_if_not(boost::make_counting_iterator(2u),ce, bind(std::modulus<unsigned>{},val,_1)); } }; int main(){ std::copy_n(boost::make_filter_iterator(is_prime{},boost::make_counting_iterator(1u) // if the following line is omitted we have undefined behavior, because of uninitialized unsigned value // ,boost::make_counting_iterator(std::numeric_limits<unsigned>::max()) // must be different from above value ),40,std::ostream_iterator<unsigned>{std::cout,", "}); } =====8< -- Prof. Peter Sommerlad Institut für Software: Bessere Software - Einfach, Schneller! HSR Hochschule für Technik Rapperswil Oberseestr 10, Postfach 1475, CH-8640 Rapperswil http://ifs.hsr.ch http://cute-test.com http://linticator.com http://includator.com tel:+41 55 222 49 84 == mobile:+41 79 432 23 32 fax:+41 55 222 46 29 == mailto:peter.sommerlad@hsr.ch

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[compond_file_binary] Gauging interest in a possible library submission.
by А В 06 Dec '12

06 Dec '12

Hi, all. Is there any interest in a cross-platform C++ library which allows to create/read/write binary compound files? Briefly, compound file is filesystem for storing files and directories within a single file on a disk. Initially compound file format is developed by Microsoft and now is the part of Microsoft's Open Specifications Documentation. Compound files are used across various platforms and applications, and not restricted by some specific domain. In general, any application can store information in such a way. I've found on the Internet interest in such library and decided to implement it. Additional information can be found here: Article on the Wikipedia: http://en.wikipedia.org/wiki/Compound_File_Binary_Format Benefits of Compound Files: http://msdn.microsoft.com/en-us/library/windows/desktop/aa378938(v=vs.85).a… [MS-CFB] Open specification for compound files: http://msdn.microsoft.com/en-us/library/dd942138.aspx Regards, Alexander Voitenko.

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[BGL] status of maximum adjacency search
by Fernando Vilas 03 Dec '12

03 Dec '12

Hi, What remains to get ticket 6780 ready to commit? -- Thanks, Fernando Vilas fvilas(a)iname.com

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Re: [boost] [locale] [filesystem] Windows local 8 bit encoding
by Thiel, Bjoern 30 Nov '12

30 Nov '12

Hi Artyom, > Currently win32 API supports only UTF-8 encodings, so you need to one of: > > - compile with ICU > - select std backend (because the default without ICU on windows is win32) > - disable win32 backend (in build options) so only std backend would be used. But you should note that under > Windows only MSVC has std backend support, for gcc and ANSI encodings you need ICU, Is there reason why win32 and std backend behave differently here? Using std locale get_system_locale() method works for code pages of the form 'windows-XXX'. Others e.g. 'Shift_JIS' should fail. And if you want the CURRENT locale on Microsoft Windows, I simply can't see how to get that. But why not add generator.generate( void ) giving exactly that. Best regards Bjoern.

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[mpl] Determining when a type is a placeholder expression
by Edward Diener 30 Nov '12

30 Nov '12

Is there any way to determine when a type is an MPL placeholder expression ? I can determine whether a type is a metafunction class ( it has a class template called 'apply' ), but I can't think of any sure way to determine whether or not a type is a placeholder expression. Ideally if a type in one of my templates is an MPL lambda expression ( its either a metafunction class or placeholder expression ) I want to invoke it with some compile-time data, otherwise I want to do something else with that type. Of course a less elegant solution is to have another template boost::mpl::bool_ parameter telling which it is but I was hoping to avoid it if I can figure it out myself.

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