September 2013 - Boost - lists.preview.boost.org

Is there any interest in a library for actor programming?
by Charousset, Dominik 28 May '14

28 May '14

Hi, is there any interest in a library for actor programming? The library we've developed is a C++11 open source library named "libcppa". It is currently released under LGPL2, but re-releasing the library under the boost license is not an issue. You'll find all important links and ressources either under http://libcppa.org or on the GitHub project page: https://github.com/Neverlord/libcppa, including a user manual as HTML or PDF. We've also submitted a paper to the C++Now conference. What is actor programming? For those of you who aren't yet familiar with the actor model: actors basically represent tasks or services that communicate via message passing. In libcppa, actors are very lightweight (you can spawn literally millions of them) and scheduled cooperatively using a thread pool (although actors are allowed to opt-out of the cooperative scheduling). Some of the main strengths of this programming paradigm are: (1) network transparency, (2) race conditions are avoided by design, (3) a strong failure model that enables developers to build reliable distributed systems, and (4) the actor model addresses both concurrency (multiple actors on one host) and distribution (any number of actors on any number of hosts). Here's the classical hello world example: ---------------------------------------------------------------------------------- #include <string> #include <iostream> #include "cppa/cppa.hpp" using namespace std; using namespace cppa; void mirror() { // wait for messages become ( // invoke this lambda expression if we receive a string on_arg_match >> [](const string& what) { // prints "Hello World!" via aout (thread-safe cout wrapper) aout << what << endl; // replies "!dlroW olleH" reply(string(what.rbegin(), what.rend())); // terminates this actor ('become' otherwise loops forever) self->quit(); } ); } void hello_world(const actor_ptr& buddy) { // send "Hello World!" to our buddy ... sync_send(buddy, "Hello World!").then( // ... and wait for a response on_arg_match >> [](const string& what) { // prints "!dlroW olleH" aout << what << endl; } ); } int main() { // create a new actor that calls 'mirror()' auto mirror_actor = spawn(mirror); // create another actor that calls 'hello_world(mirror_actor)' spawn(hello_world, mirror_actor); // wait until all other actors we have spawned are done await_all_others_done(); // run cleanup code before exiting main shutdown(); } ---------------------------------------------------------------------------------- A message is simply a tuple of values that is pattern matched at the receiver. For example, " on_arg_match >> [](const string& what) {...}" defines a message handler that is called whenever a tuple with one single string element arrives. "on_arg_match" simply defines a pattern that matches the signature of the given lambda. Please have a look at the examples folder on GitHub (https://github.com/Neverlord/libcppa/tree/master/examples) or at the user manual (http://neverlord.github.io/libcppa/manual/) if you want to see more examples. Best regards, Dominik Charousset

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required toolsets
by Steven Watanabe 15 May '14

15 May '14

AMDG The list of required toolsets in explicit-failures-markup.xml is out-dated. Therefore, if no one objects, I propose setting it to the following: msvc-10.0, msvc-11.0, gcc-4.6, gcc-4.7, clang-darwin-11, clang-darwin-4.2.1, clang-linux-3.1, clang-linux-3.2, gcc-mingw-4.7, gcc-mingw-4.6 (two releases of each major compiler that appears in both the trunk and release regression tests) The sole effect of this is to determine which toolsets appear in the issues list: http://www.boost.org/development/tests/trunk/developer/issues.html In Christ, Steven Watanabe

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C++03 and C++11 ABI compatibility for compiled libraries
by Andrey Semashev 24 Jan '14

24 Jan '14

Hi, I would like to raise the issue of binary compatibility of compiled Boost libraries between C++03 and C++11. I faced this problem with gcc on Linux, but other compilers and platforms may be affected as well. To summarize the problem: * Most, if not all Linux distributions build packages in C++03 mode. This is also the default in gcc. * Some Boost libraries conditionally use C++11 features in their binary interfaces (see [1] as an example). This makes C++03 and C++11 versions of the library binary incompatible. * Given that, users are unable to use C++11 in their code that uses Boost because of linker failures. I don't have the complete list of the offending C++11 features that break ABI, but it would seem that at least scoped enums and rvalue references are among them. Are there any more? I would like to hear opinions on the possible course of action to tackle this problem. Currently, I see 2 choices: 1. Avoid using C++11 features in binary interfaces. This may also mean avoiding STL types in binary interfaces, if they differ between C++03 and C++11 (I didn't verify that). This is my suggested hotfix solution for Boost.Filesystem [1] and the approach I took in Boost.Log. Obviously, this cripples code and error prone, but it keeps a single binary that can be used from any flavor of C++ on the user's side. 2. Compile different versions of Boost libraries, for each supported C++ version. The C++ version should be encoded into the library file names, so that different versions can coexist. This would require changes in Boost.Build and autolinking support code, but I think this would be a better long-term solution. Opinions? [1] https://svn.boost.org/trac/boost/ticket/6779

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[block_ptr] & Java
by Phil Bouchard 14 Jan '14

14 Jan '14

Hello everyone, In a quest to speed up my Android applications and knowing Java is written in C++, I decided to discuss with the OS community openjdk.java.net to try to introduce them block_ptr. But the conversation was dead in the water probably due to the lack of developers. So I just have questions: - Does anybody know if Java uses Boost? - block_ptr hasn't been reviewed yet but memory management is an important subject. Are there unanswered questions about it? Sincerely, -Phil Experiment proposal to refute Special Relativity for the interested: http://finitetheory.com/files/experiment.pdf

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[Macro]Test Case grouping using Traits
by Hemanth Choudary M V (RBEI/ETA1) 13 Jan '14

13 Jan '14

Hello, I have observed that in native unit test framework(c++), there is an option to group test cases using attributes which are reflected as traits in the Test Explorer window in MS VS2012. Following is a an example of the same: BEGIN_TEST_METHOD_ATTRIBUTE(TestMethod3) TEST_OWNER(L"SuperMan") TEST_PRIORITY(2) TEST_METHOD_ATTRIBUTE(L"Category",L"Slow") END_TEST_METHOD_ATTRIBUTE() TEST_METHOD(TestMethod3) { Assert::AreEqual(2,6); } How can this be achieved via Boost Unit Test Library? Are there macros to achieve the same? Mit freundlichen Grüßen / Best Regards, Hemanth Choudary MV RBEI/ETA1

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[Test] Problems with debug::break_memory_alloc
by Fredrik Orderud 13 Jan '14

13 Jan '14

I have a problem with the memory-leak detection logic in boost.test. What happens when unit_test::framework::init starts up on Windows is that memory-leak detection is first explicitly activated. Secondly, debug::break_memory_alloc is called with a value (default is 1). Activation of leak detection is great, but to always override the allocation number to break on is not necessary a good idea if the user has already set a value from a debugger. In my case I am investigating a leak from a static member allocated prior to main and/or boost.test being invoked. In that case, I need to break the program early to be able to set the allocation number to break on. This works well by itself, but it's _very_ confusing when boost.test afterwards replaces my allocation number with a default value. Could it be possible to modify boost.test, so that it only modifies the allocation number to break on if the user has explicitly requested to break on a given allocation? Thanks in advance, Fredrik Orderud

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[test] still broken in release
by Tim Blechmann 30 Dec '13

30 Dec '13

hi all, i've reported an issue before that boost.test in the release branch is pretty broken. *all* tests of the boost.heap testsuite segfault like this: --Program received signal SIGSEGV, Segmentation fault. 0x00000000005f4975 in boost::unit_test::test_suite::add (this=0x8cefa0, tu=0x9, expected_failures=0, timeout=0) at ../../../boost/test/impl/unit_test_suite.ipp:139 139 m_members.push_back( tu->p_id ); (gdb) bt #0 0x00000000005f4975 in boost::unit_test::test_suite::add (this=0x8cefa0, tu=0x9, expected_failures=0, timeout=0) at ../../../boost/test/impl/unit_test_suite.ipp:139 #1 0x00000000005fda9c in boost::unit_test::ut_detail::test_init_caller::operator() (this=0x8d4e08) at ../../../boost/test/impl/framework.ipp:96 #2 0x00000000006031a2 in boost::unit_test::ut_detail::invoker<int>::invoke<boost::unit_test::ut_detail::test_init_caller> (this=0x7fffffffc36f, f=...) at ../../../boost/test/utils/callback.hpp:42 #3 0x0000000000603071 in boost::unit_test::ut_detail::callback0_impl_t<int, boost::unit_test::ut_detail::test_init_caller>::invoke (this=0x8d4e00) at ../../../boost/test/utils/callback.hpp:89 #4 0x000000000060e03d in boost::unit_test::callback0<int>::operator() (this=0x7fffffffcfc0) at ../../../boost/test/utils/callback.hpp:118 #5 0x000000000060de8a in boost::detail::do_invoke<boost::scoped_ptr<boost::detail::translate_exception_base>, boost::unit_test::callback0<int> > (tr=..., F=...) at ../../../boost/test/impl/execution_monitor.ipp:281 #6 0x000000000060d1a8 in boost::execution_monitor::catch_signals (this=0x7fffffffcfd0, F=...) at ../../../boost/test/impl/execution_monitor.ipp:885 #7 0x000000000060d262 in boost::execution_monitor::execute (this=0x7fffffffcfd0, F=...) at ../../../boost/test/impl/execution_monitor.ipp:1211 #8 0x00007ffff7b0bf33 in boost::unit_test::framework::init (init_func=0x4e3f30 <init_unit_test()>, argc=1, argv=0x7fffffffd198) at ../../../boost/test/impl/framework.ipp:268 #9 0x00007ffff7b22267 in boost::unit_test::unit_test_main (init_func=0x4e3f30 <init_unit_test()>, argc=1, argv=0x7fffffffd198) at ../../../boost/test/impl/unit_test_main.ipp:177 #10 0x00000000004e3f62 in main (argc=1, argv=0x7fffffffd198) at ../../../boost/test/unit_test.hpp:59 -- boost.test in trunk works fine, though ... i wonder, will it eventually be merged to release? tim

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[test] Interest in 'hamcrest'-style checks?
by Jared Grubb 29 Dec '13

29 Dec '13

I recently read "Modern C++ Programming with Test-Driven Development", and I really enjoyed this book and highly recommend it. One of the styles I saw for the first time was "hamcrest"-style assertions. ("Hamcrest" is an anagram of "matchers"; also see http://en.wikipedia.org/wiki/Hamcrest.) For a quick idea, imagine there is a BOOST_CHECK_THAT macro that looks like this: (excuse my choice of names here, we can pick better ones if people like the idea) BOOST_CHECK_THAT( str, IsEqualTo(expStr) ); BOOST_CHECK_THAT( str, HasSubstring(needleStr) ); BOOST_CHECK_THAT( str, Not(HasSubstring(badStr)) ); BOOST_CHECK_THAT( vec, Contains(42) ); Comparing them to current boost::test assertions, usually the two are directly equivalent, and it's just a matter of style. At first, I was unconvinced of a need for this. However, there are a few scenarios where the hamcrest-style actually are really helpful: BOOST_CHECK_THAT(vec, Any(Contains(42), Contains(-42)) ); BOOST_CHECK_THAT(str, All(StartsWith("abc"), HasSubstring("lmnop"), EndsWith("xyz")) ); BOOST_CHECK_THAT(count, All(GE(0), LT(10)) ); BOOST_CHECK_THAT(vec, HasSubsequence(otherVec) ); BOOST_CHECK_THAT(vec, Sorted(IsEqualTo({1, 2, 3})) ); BOOST_CHECK_THAT(optionalStr, Any(IsEqualTo(boost::none), Deref(IsEqualTo("str"))); Sure, almost all of this is already doable: BOOST_CHECK_EQUAL_COLLECTIONS( /* sorry, but I really dislike this one :) */ ); BOOST_CHECK( std::count(vec.begin(), vec.end(), 42) && std::count(vec.begin(), vec.end(), -42) ); And, yes, you can create a helper functors today: BOOST_CHECK( Contains(vec, 42) && Contains(vec, -42) ); But hamcrest still gives these advantages over even that: * Dont repeat yourself: -- the value under test appears only once in the check expression; this is really helpful if you want to test an expression ("future.get()") that can only be called once * Better diagnostics: -- when something fails, you can get a detailed error (eg: "blah does not contain the element blah" or "str does not start with blah") -- when you have "Any" conditions, "errors" get squashed if some other condition passes, but all are shown if none pass -- composed tests can provide nested diagnostics; eg: for All(A, Any(B,C)), you'd get something like "'...A...' is true, but none of { '...B...' , '...C...' } are true", but spread over many lines -- and even with indentation if we want * Intentional Asymmetry: Is it BOOST_CHECK_EQ(expected, actual) or (actual, expected)? It really doesnt matter in the end, but a message like "expected 34, got 33" is actually kinda nice. Putting the value under test at the start creates an asymmetry that helps guide the user to put the values in the "right" order. * Composability * Extendibility: once the facility is there, its actually really easy to write more ("CanLockMySemaphoreType(timeout)") I wasnt able to find any discussion on boost's list for this, so I thought I'd bring it up. As for difficulty, implementing the examples above is actually already quite easy using boost::test predicates, and the extra macro would be fairly simple to implement. Almost all the work would be in creating the library of matchers, which is the fun part :) What do you think? Jared

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[boost.test] Correct usage?
by Philip Bennefall 29 Dec '13

29 Dec '13

Hello, I just started writing unit tests for a large project that I am involved in, and boost.test has been absolutely fantastic to work with so far. True the documentation could be clearer, but as far as functionality I am very much impressed with the library. I have a question though. I read the following: http://lists.boost.org/Archives/boost/2011/10/186439.php This concerns me. What is the status here? When I build boost_1_54_0, in my stage/lib directory I see: libboost_test_exec_monitor-vc100-mt-s-1_54.lib My test cases look as follows: #define BOOST_TEST_MODULE MyProgram #include <boost/test/unit_test.hpp> BOOST_FIXTURE_TEST_SUITE(basic_operations, basic_memory_logger) BOOST_AUTO_TEST_CASE( some_test ) { // ... // Using BOOST_REQUIRE_EQUAL, BOOST_CHECK_EQUAL, BOOST_CHECK, BOOST_REQUIRE_EQUAL_COLLECTIONS and friends here. } BOOST_AUTO_TEST_SUITE_END() My questions are: 1. Are all these macros still supported and not depricated? 2. Is the structure correct? Am I depending on something depricated? Am I including the right header? I am linking with the library mentioned above (via auto-linking), which is why I am concerned about deprication. Thanks in advance for any clarification on this. Kind regards, Philip Bennefall

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[filesystem] fix recur_dir_itr_imp::increment(system::error_code* ec) in 1.54.0
by claudio.bley＠gmail.com 19 Dec '13

19 Dec '13

Hi. What's happening to the filesystem library? It seems there's no progress on any tickets in the bug tracker? Referring to https://svn.boost.org/trac/boost/ticket/6821#comment:5 Could we get this fix into 1.54.0, please? BTW, sorry for any confusion - I "managed" to comment on the wrong ticket... https://svn.boost.org/trac/boost/ticket/5403 would've been more appropriate, I guess. Claudio -- Claudio

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