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boost python AttributeError
by Chien-Yu Chen 03 Apr '22

03 Apr '22

hi I followed the basic boost python examples, both hello_ext.greet() and hello.World() and both are giving me AttributeError error, like AttributeError: module `hello` has no attribute 'greet' dumpbin does show that I have PyInit_hello exported out. Please let me know if I am doing something wrong as this should be trivial. thx -- Any MicroSoft extension file will directly go to trash without any warning and regret.

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Fwd: Concatenated input streams
by Robert Dodier 29 Mar '22

29 Mar '22

Hi, I'm interested in working with an input stream which comprises multiple input streams. The resulting stream comprises all of the input from the first stream (until EOF), then all of the input from the second, etc. For what it's worth, such an input stream is called a concatenated input stream in at least one other context (namely Common Lisp). The input streams in question are file input streams, although conceptually I don't know if that changes anything. I am hoping to find something equivalent to $ cat file1 file2 file3 ... > alldata and then reading alldata. Is there a Boost class which implements such a thing? I know that this is a pretty simple concept, and therefore it's just a small matter of programming, but I'm hoping that someone has already worked out the details. If there is such a thing in some library other than Boost, I would be interested to hear about that too. Thank you for your time, I appreciate your help very much. Robert Dodier

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[Boost.Asio] Can I move io_context away while having sockets bound to it?
by B Aleck 22 Mar '22

22 Mar '22

You created serveral sockets and bound them to an io_context Is it safe to std::move the io_context away? Will those sockets be affected, or even be invalidated?

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Curious definition of beast::file_mode::append
by Senthil Cheetancheri 18 Mar '22

18 Mar '22

Hi All, The current definition of append seems to be identical to that of write. Both are defined as follows: 1. Create a new file if it doesn't exist. 2. Truncate to zero bytes, if it exists. The comment for append says, "The current file position shall be set to the end of the file prior to each write." However, if the file is always truncated to zero, implementing the above comment achieves nothing significant. Shouldn't append simply open an existing file or create a new one for writing and set the file-pointer to the end of the file? This will also obviate the need for append_existing. Following the same line of reasoning for write: The comment says that this mode permits random-access reading and writing for the specified file. However again, if the size is always truncated to zero bytes, random-access reading or writing becomes a moot point. On the other hand, if write is defined not to truncate (as I expected originally), it will obviate the need for write_existing as well. Am I misunderstanding these definitions? Is there a sound reason behind the current definitions? Thanks, Senthil.

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numeric_cast should work with enum's
by Frederick Virchanza Gotham 16 Mar '22

16 Mar '22

(Sometimes Gmail changes white space so I hope this post is indented properly) I think that "numeric_cast" should be able to cast to and from enum types, so that it can be used as follows: #include <cstdint> #include <iostream> using std::cout; using std::endl; enum class Frog { Blue, Yellow, Pink = 0xFFFFu }; enum class Toad : std::uint8_t { Purple, Orange = 0x7f }; int main(void) { try { numeric_cast<Toad>( Frog::Pink ); } catch(std::exception const &e) { cout << e.what() << endl; } std::uint32_t my_32_bit_var = 0xffffffffU; try { numeric_cast<std::uint16_t>(my_32_bit_var); } catch(std::exception const &e) { cout << e.what() << endl; } try { numeric_cast<std::uint8_t>( Frog::Pink ); } catch(std::exception const &e) { cout << e.what() << endl; } try { numeric_cast<Toad>(0x1FFu); } catch(std::exception const &e) { cout << e.what() << endl; } } In order to achieve this behaviour, I've created my own "numeric_cast" in the global namespace as follows: #include <type_traits> // is_enum, underlying_type #include <boost/numeric/conversion/cast.hpp> // numeric_cast template<bool T_is_an_enum, typename T> struct numeric_cast_helper { typedef T type; }; template<typename T> struct numeric_cast_helper<true, T> { typedef typename std::underlying_type<T>::type type; }; template<typename A, typename B> A numeric_cast(B const b) { return static_cast<A>( boost::numeric_cast<typename numeric_cast_helper<std::is_enum<A>::value, A>::type> ( static_cast<typename numeric_cast_helper<std::is_enum<B>::value, B>::type>(b) ) ); } Should the Boost Numeric library be changed so that numeric_cast can work with enum's?

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[release] Boost 1.79.0 beta 1 released
by Marshall Clow 16 Mar '22

16 Mar '22

Boost release 1.79.0 beta 1 is now available at: <https://boostorg.jfrog.io/artifactory/main/beta/1.79.0.beta1/source/> The SHA256 checksums are as follows: 8985105623f48d55be01076d98ca4e7a8cb548a8d7f9ad0e1fc3c710d2c75fcf boost_1_79_0_b1.tar.bz2 4b58e4d3b6ff1176b3c6cb9eec496c1f6d2535270e97ec140da533d68766ca39 boost_1_79_0_b1.tar.gz 4d05b458cd039afe86003cf7e1e6c3a358b5b2d031892e620eedc344ab200246 boost_1_79_0_b1.7z 768875ad5c77763445e8b119072cfa1e64854b071a353dd44c3c73ff46df910b boost_1_79_0_b1.zip For details of what's in the release, see <https://www.boost.org/users/history/version_1_79_0.html>. Please download the beta, give it a try, and report any problems you encounter. Thanks, -- The Boost Release Team

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container: static_vector and type traits
by MM 15 Mar '22

15 Mar '22

Hello Should static_vector be of standard layout and/or trivially copyable? depending on the element type I see this outputs false std::cout << std::is_standard_layout_v<boost::container::static_vector<char,32>> << std::endl; std::cout << std::is_trivially_copyable_v<boost::container::static_vector<char,32>> << std::endl; Rds,

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Boost.ASIO SSL Version?
by Osman Zakir 10 Mar '22

10 Mar '22

What version of OpenSSL does Boost.ASIO use? And may I suggest to consider upgrading to the latest version if that hasn't been done already (if it's not too much trouble)? I tried to use version 3.0.1 (LibreSSL 3.4 is already out but according to openssl.org, their official latest version is 3.0.1? I'm not sure.) with this project of mine: https://github.com/DragonOsman/currency_converter and got these errors: " 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\error.ipp(43,28): error C4996: 'ERR_func_error_string': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(54,29): error C4996: 'RSA_free': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(60,28): error C4996: 'DH_free': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(962,29): error C4996: 'd2i_RSAPrivateKey_bio': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(965,29): error C4996: 'PEM_read_bio_RSAPrivateKey': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(978,13): error C4996: 'SSL_CTX_use_RSAPrivateKey': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(1056,9): error C4996: 'SSL_CTX_use_RSAPrivateKey_file': Since OpenSSL 3.0 1>C:\local\boost_1_78_0\boost\asio\ssl\impl\context.ipp(1122,23): error C4996: 'PEM_read_bio_DHparams': Since OpenSSL 3.0 " Or should I stick to version 1.1.1m? Thanks for any replies.

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Vertical slopes and Cubic Hermite Interpolation
by Cory Riddell 08 Mar '22

08 Mar '22

I'm reading about boost::math::interpolators::cubic_hermite and the constructor takes three arguments: x values, y values and slopes (dy/dx). Can this library be used when the slope at a point is vertical? If so, how do you specify that? I tried std::numeric_limits<double>::infinity() but that doesn't work. Cory

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[Boost.Serialization] Exception during serialization through base pointer DLL & EXE
by Marc Viala 07 Mar '22

07 Mar '22

Hi, On our platform (VS2019, Windows x64, Boost 1.77) an exception occurs during the serialization of an instance through its base pointer. This error is systematic and I was able to reproduce w/ a minimal use test (cf. enclosed archive). This use case includes a solution w/ a DLL project and EXE project. The EXE project is a simple unit-test. On my platform when I execute the executable, I trigger an exception from Boost.Serialization ("unregistered void cast class cpe::derived_t<-class cpe::object_t"). I tried every recommandation that we can find on SO and Boost mailing lists without success. To be accurate, I prefer to mention that we are using Boost.Serialization Static Library flavor. Any help would be appreciated. -- Marc Viala

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