February 2018 - Boost-users - lists.preview.boost.org

Mailman upgrade
by Sys Admin - Boost 08 Feb '18

08 Feb '18

All, Per https://bugs.launchpad.net/mailman/+bug/1747209, Ciere staff will install 2.1.26 beginning 9-Feb-2018 04:00 UTC. While the maintenance is performed, incoming messages to the mailing lists for Boost will be temporarily blocked. This may result in “temporarily unable to deliver” messages received by senders if a message is delivered during the upgrade. The upgrade is expected to finish by 9-Feb-2018 05:00 UTC. Thanks, Brad Johnson Your Friendly Mailing List Admin

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[test] data driven test fails to compile when number of samples greater than 9
by Georgios Sermaidis 08 Feb '18

08 Feb '18

Hello, I am having trouble compiling a simple data driven test with 10 samples. I am using clang++ (Apple LLVM version 9.0.0 (clang-900.0.39.2))with C++14 flags enabled. According to this help page http://www.boost.org/doc/libs/1_66_0/libs/test/doc/html/boost_test/utf_refe… <http://www.boost.org/doc/libs/1_66_0/libs/test/doc/html/boost_test/utf_refe…> my compiler should have no problem dealing with number of samples greater than BOOST_TEST_DATASET_MAX_ARITY which is 10 by default. Even defining BOOST_TEST_DATASET_MAX_ARITY to 20 prior to including any headers still fails to compile with the following error: /usr/local/include/boost/test/data/test_case.hpp:182: error: no matching function for call to 'bind' boost::bind( &TestCase::template test_method<Arg...>, ^~~~~~~~~~~ Any ideas how to fix it? Here is the code: #define BOOST_TEST_MODULE dataset_example68 #define BOOST_TEST_DYN_LINK #include <boost/test/unit_test.hpp> #include <boost/test/data/test_case.hpp> #include <boost/test/data/monomorphic.hpp> #include <sstream> namespace bdata = boost::unit_test::data; BOOST_DATA_TEST_CASE( test1, bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ) ^ bdata::make( { 1, 2, 3, 5 } ), sample1, sample2, sample3, sample4, sample5, sample6, sample7, sample8, sample9, sample10) {} Thank you!

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[log] Setting log format with string
by Dirk Van Haerenborgh 07 Feb '18

07 Feb '18

Hi, I'm trying to simply set the log format of the sinks using a string. For example from a config file or just in code. Take for instance this simple line taken from the basic_example (https://github.com/boostorg/log/blob/master/example/basic_usage/ main.cpp) logging::add_console_log(std::clog, keywords::format = "%TimeStamp%: %Message%"); Whenever I add %Timestamp% to the log format, I keep getting this error: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::gregorian::bad_year> >' what(): Year is out of valid range: 1400..10000 I can easily reproduce this by running these examples (without modification): https://github.com/boostorg/log/blob/master/example/basic_usage/ main.cpp https://github.com/boostorg/log/blob/master/example/ settings_file/main.cpp Am I doing something wrong? I have this same behaviour on both boost1.62 and boost1.65. The former as installed from the debian package manager. The latter was manually compiled... -Dirk

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[intrusive] list compatibility with existing application-defined intrusive lists
by Rahul Ramadas 04 Feb '18

04 Feb '18

Hi all, boost::intrusive lists can be easily customized to be compatible with an existing doubly-linked intrusive list implementation, such as the one used in the linux kernel (struct list_head). Indeed, I have been able to declare and use a boost::intrusive::list of my own with custom traits that uses struct list_head as the underlying representation, enabling me to simply use .end().pointed_node() to get access to the list head and pass it to legacy C code that expects a struct list_head*. However, I can't think of a way to achieve interoperability in the opposite direction. For example, I have an existing function (to be precise, a callback that I pass to legacy C code), that accepts a struct list_head* that is expected to contain a list of elements of a certain type. I want some way to "wrap" this raw pointer in a type-safe intrusive list type that I use as naturally as a boost::intrusive::list (iteration, modification, etc.). I see no way to achieve this. The way I see it, what I need is a boost::intrusive::list_ptr, a container that doesn't actually own the list head, but rather, points to a list head stored elsewhere. It would have the same interface as a list, allowing me to push_back, clear, etc., but behaves as a pointer when it comes to moves and copies. Additionally, there should also be a boost::intrusive::const_list_ptr, which will not allow me to modify the list, but still allows iteration and other non-modifying operations. Unless, of course, there are already existing mechanisms to achieve this. If anyone has any ideas, please let me know. Thanks.

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Boost Python with Continuum Anaconda?
by Stephen Gray 02 Feb '18

02 Feb '18

I'm trying to get started with Boost Python. I've built the Boost Python libraries and linked a simple test programme with embedded Python. My Python environments are managed by Anaconda. There are errors at runtime as detailed in this Stackoverflow posting: https://stackoverflow.com/questions/48552092/boost-python-embedding-error Can anyone please help me understand what the issue is and how to solve it? With thanks.

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asio: cancelling a named pipe client
by Stian Zeljko Vrba 01 Feb '18

01 Feb '18

I have a client which connects to a named pipe as follows: CreateFile(pipeName.c_str(),GENERIC_READ | GENERIC_WRITE, 0, nullptr, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, nullptr); The result of this call is assigned to a stream_handle. I want that io service shuts down orderly by run() returning due to running out of work. To achieve this, I post a lambda that effectively calls cancel() on the handle (hidden inside Kill()): _io.post([this]() { for (auto& w : _workers) w->Kill(); }); However, cancel() has no effect: the callback for async_read continues to return with error code of zero and data read from the pipe. For reference, this is the read call with its handler: template<typename T> void read(T& ioh, const asio::mutable_buffer& buf) { ioh.async_read_some(asio::buffer(buf), [this, self = shared_from_this()](const boost::system::error_code& ec, size_t sz) { if (ec == boost::system::errc::operation_canceled) return; if (ec) QUINE_THROW(Error(self->_ownersId, ec, "async_read_some")); self->ReadCompleted(sz); }); } ReadCompleted() processes the received data and loops by calling read() again. If I call close() the callback gets an error code and everything works out correctly, *except* that I get an error code [invalid handle] that gets logged as an error (though it's not). Am I correct in assuming that cancel() is an apparent noop in this case because of the race-condition where an I/O request completes successfully before cancel is invoked? If so, can you suggest a more elegant way (i.e., a way that doesn't induce a hard error) of exiting a loop as described here? Setting a member variable instead of calling cancel? Given the existence of the race-condition, what are use-cases for cancel? How to use it correctly, if at all possible? -- Stian

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Using Boost 1.66 with VS2017
by Tim Burgess 01 Feb '18

01 Feb '18

Hi, I'm getting the following message during compilation of my application: 1>Info: Boost.Config is older than your compiler version - probably nothing bad will happen - but you may wish to look for an update Boost version. Define BOOST_CONFIG_SUPPRESS_OUTDATED_MESSAGE to suppress this message. I don't want to suppress the message, but would appreciate any mods I need to do to actually stop its cause. Many thanks in advance for any suggestions. Best wishes. Tim Burgess

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