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Boost.Optional error should be a warning
by Michael Powell 14 Jan '19

14 Jan '19

Hello, I am using Boost.Optional, and, while I do want to "include it in an output", the library which I am doing so has another mechanism to do so. Translation, for Optional purposes, the following assertion should be a warning, IMO, and not an error: BOOST_STATIC_ASSERT_MSG(sizeof(CharType) == 0, "If you want to output boost::optional, include header <boost/optional/optional_io.hpp>"); Cheers, Michael Powell

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Boost.Units: Is it possible to convert on assignment without casting?
by Carel Combrink 14 Jan '19

14 Jan '19

Hi. I have two unit quantities defined as follow: static const auto Hz = boost::units::si::hertz; static const auto KHz = boost::units::si::kilo * Hz; using Hertz = boost::units::quantity<decltype( Hz ), double>; using Kilohertz = boost::units::quantity<decltype( KHz ), double>; Assigning one type to another does not compile: Kilohertz freqKhz = Kilohertz::from_value( 1.234 ); Hertz freqHz = freqKhz; >>> error: conversion from 'Kilohertz {aka boost::units::quantity<...>, double>}' to non-scalar type 'Hertz {aka boost::units::quantity<...>, double>}' requested [1] Is this possible, should it be enabled or is it not supported? I am using boost 01.67, Mingw 5.3 and MSVC 2017 (C++14) The following options work as expected: Hertz freq1 = static_cast<Hertz>( freqKhz ); Hertz freq2 = Hertz( freqKhz ); But this adds a bit more code to maintain and keep in sync, one thing one tries to avoid when using the library since one needs to keep the LHS and the RHS of the opertor= in sync. PS: The chrono library allows this type of conversion given there is no information lost (but for double as storage types this should not be the case) std::chrono::seconds sec = std::chrono::seconds { 10 }; std::chrono::nanoseconds nsec = sec; [1] https://gcc.godbolt.org/z/0sTHQQ Regards, Carel

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Forcing boost to build zlib
by Simon Michalke 12 Jan '19

12 Jan '19

Hello, what is needed to force bjam to build zlib? Is the zlib.h enough? Also is there a way to make bjam fail compiling if I set "NO_ZLIB=0" and it does not find the zlib.h / source? It is really inconvenient that bjam silently switches off zlib without any error or warning why zlib is not being build. My commands are: ./bootstrap.sh --without-libraries=python --prefix=/home/simon/code/cfs/release_mingw_openblas/cfsdeps/boost/install --with-toolset=gcc --without-libraries=context --without-libraries=coroutine target-os=windows architecture=x86 address-model=64 release and ./b2 target-os=windows architecture=x86 address-model=64 release --user-config=user-config.jam toolset=gcc-mingw -s ZLIB_BINARY=\"/home/simon/code/cfs/release_mingw_openblas/lib64/MINGW_X86_64/libzlibstatic.a\" -s ZLIB_INCLUDE=\"/home/simon/code/cfs/release_mingw_openblas/include\" -s NO_ZLIB=0 threading=multi install (this is cross compiling, but I have the same problem building for Linux) Regards, Simon

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Possible Boost.Variant issue with JSON AST
by Michael Powell 11 Jan '19

11 Jan '19

Hello, I've got an AST I am developing to support JSON parsing using the latest VC++ (15.9.5), however, I am having difficulty persuading the compiler with my forward declarations. i.e. 1>d:\dev\boost.org\boost_1_69_0\boost\mpl\sizeof.hpp(27): error C2027: use of undefined type 'kingdom::json::object_t' In terms of JSON AST modeling, the rub appears to be in a couple of places: defining the JSON AST Array, and making the JSON AST Object available to Value. Re: semantic terminology, Value is interchangeable with Element, in view of the JSON grammar. Here's my attempt at a flattened single source example: https://wandbox.org/permlink/83c3VXZ4W1DHoEBc I seem to recall there being future issues with C++ forward declarations, but this seems to be like a bad language design decision to restrict this, especially in light of this kind of approach. I'm not sure how better to sort this out. At minimum, at least Value needs a forward declaration depending on how I arrange my headers, includes, etc. But then I still run into Value forward declaration undefined type issues. I'm not sure it's as much a language issue as much as it is possible a Boost.Variant issue, per se. Suggestions? Thanks! Michael Powell

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[Spirit] Incompatible skipper type?
by Michael Powell 10 Jan '19

10 Jan '19

Hello, I'm a bit confused here, not sure what this means: Severity Code Description Project File Line Suppression State Error C2664 'bool boost::function4<R,T0,T1,T2,T3>::operator ()(T0,T1,T2,T3) const': cannot convert argument 4 from 'const Skipper' to 'T3' Kingdom.Json.Parser.Tests d:\dev\boost.org\boost_1_69_0\boost\spirit\home\qi\nonterminal\rule.hpp 304 // If you are seeing a compilation error here stating that the // fourth parameter can't be converted to a required target type // then you are probably trying to use a rule or a grammar with // an incompatible skipper type. if (f(first, last, context, skipper)) {} Incompatible where? How? Requires clarification please. The default Skipper type, which I am using at the moment, is boost::spirit::qi::space_type. I aim to use the proven Comment Skipper that I leveraged in a previous iteration eventually, but I expect that compilation should work with the simple space type at least. Because as far as I can determine all of the rules in my Grammar have the same Skipper type. struct json_grammar : qi::grammar<It, value_t(), Skipper> { using iterator_type = It; using skipper_type = Skipper; using char_rule_type = qi::rule<It, char()>; json_grammar() : json_grammar::base_type(value_) { // ... } private: struct escapes_t : qi::symbols<char, char> { escapes_t() { this->add("\\b", '\b') ("\\f", '\f') ("\\n", '\n') ("\\r", '\r') ("\\t", '\t') ("\\v", '\v') ("\\\\", '\\') ("\\/", '/') ("\\'", '\'') ("\\\"", '"') ; } } char_esc; //qi::rule<iterator_type> line_cont; char_rule_type hex_esc, unicode_esc; qi::rule<iterator_type, str_t()> quot_str, tick_str, str_lit; qi::rule<iterator_type, std::vector<value_t>(), skipper_type> array_; qi::rule<iterator_type, boost::tuple<key_t, value_t>(), skipper_type> member; qi::rule<iterator_type, std::vector<boost::tuple<key_t, value_t>>(), skipper_type> object_; qi::rule<iterator_type, key_t(), skipper_type> member_key; qi::rule<iterator_type, value_t(), skipper_type> value_; qi::rule<iterator_type, numeric_sign_t(), skipper_type> numeric_sign; qi::rule<iterator_type, float_t(), skipper_type> float_lit; qi::rule<iterator_type, floating_point_number_t(), skipper_type> floating_point; qi::rule<iterator_type, int_t(), skipper_type> hex_int, oct_int, dec_int, int_lit; qi::rule<iterator_type, integer_number_t(), skipper_type> integer; qi::rule<iterator_type, boolean_t(), skipper_type> bool_lit; qi::rule<iterator_type, null_t(), skipper_type> null_lit; }; Best regards, Michael Powell

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Server application won't bind to ports on IP address other than my internal ones
by Osman Zakir 10 Jan '19

10 Jan '19

I have a server application that I wrote. It currently doesn't bind to any ports on any IP address other than my computer's internal IP addresses (the localhost and 192.168.x.x ones). The application is the one whose source code is on GitHub here<https://github.com/DragonOsman/currency_converter/>. I used the asynchronous server and client examples from the Boost.Beast GitHub repository for the networking code (this link for the server: link<https://github.com/boostorg/beast/blob/develop/example/http/server/async/ht…>; this link for the client: link<https://github.com/boostorg/beast/blob/develop/example/http/client/async/ht…>). But when I run it using my external IP address, I get the error documented on lines 471 and 472: // Bind to the server address acceptor_.bind(endpoint, ec); if (ec) { std::cerr << "Lines 471 and 472:\n"; fail(ec, "bind"); return; } with the error itself being: bind: The requested address is not valid in its context And I've heard from whoever has tried to download and then run the server application that it just closes on its own after a while. I also tried to deploy it to Heroku as a Docker container before and found that it wouldn't bind to any ports they tried to bind it to and they had to kill it with SIGKILL. I tried to look for the code for bind in Asio, but I don't really know where to look. Some help on that would also be appreciated. I might be able to figure it from reading that code. If I can't, I'll come back here.

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C++/CLI and >=VS2015
by liong＠gmx.ch 09 Jan '19

09 Jan '19

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How strong is PropertyTree JSON support
by Michael Powell 09 Jan '19

09 Jan '19

Hello, I have a requirement to support parsing JSON, and while I could potentially pull together a Spirit Qi (or even X3, possibly) based grammar, I wonder with all the idiosyncrasies, i.e. particularly strings, escape sequences, Unicode, etc, is it worth it. Then there's the Boost.PropertyTree JSON support, which I think may be an adequate fit. However, just how robust is this support when it comes to handling some of the nuanced corner cases? The harder ones I think are the potential for escape sequences, Unicode, etc, embedded within a String. i.e. https://json.org/ or, http://es5.github.io/x7.html It seems with Property Tree there are also these limitations: <docs> The property tree dataset is not typed, and does not support arrays as such. Thus, the following JSON / property tree mapping is used: * JSON objects are mapped to nodes. Each property is a child node. * JSON arrays are mapped to nodes. Each element is a child node with an empty name. If a node has both named and unnamed child nodes, it cannot be mapped to a JSON representation. * JSON values are mapped to nodes containing the value. However, all type information is lost; numbers, as well as the literals "null", "true" and "false" are simply mapped to their string form. * Property tree nodes containing both child nodes and data cannot be mapped. </docs> It seems to me that much of the limitation is in adapting the PropertyTree to the JSON structure, but mostly vice versa. Not quite fitting a square peg in a round hole, but coming quite close, I think: "If a node has both named and unnamed child nodes, it cannot be mapped to a JSON representation." We're talking about the mapping from PropertyTree to JSON here? Seems like a potentially problematic issue depending on desired usage, 'all type information is lost; numbers, as well as the literals "null", "true" and "false" are simply mapped to their string form'. I'm not sure what "nodes containing both child nodes and data" means? https://www.boost.org/doc/libs/1_69_0/doc/html/property_tree/parsers.html#p… Besides these concerns, I should think a grammar is fairly straightforward to construct, if push came to shove. It's either living with the Boost.PropertyTree or rolling my own AST, which is not outside the realm of possibility for my purposes. Thoughts? Suggestions? Thanks! Michael Powell

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Re: [Boost-users] How strong is PropertyTree JSON support
by Bjorn Reese 08 Jan '19

08 Jan '19

On 1/8/19 6:50 PM, Michael Powell via Boost-users wrote: > Thoughts? Suggestions? https://github.com/breese/trial.protocol http://breese.github.io/trial/protocol/trial_protocol/json.html

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Boost wiki - revised Boost guidance for authors on Warnings - RFC
by Paul A. Bristow 08 Jan '19

08 Jan '19

As promised at the end of a long (hijacked!) thread on 'Warnings' http://boost.2283326.n4.nabble.com/Current-Guidance-on-Compiler-Warnings-td… starting from a query by Brian Kuhl of Wind River on Boost's policy on compiler warnings, I have spent some time revising the previous guidance document on Trac that I edited many years ago. This was a long and tedious task as Markdown, as most conveniently used on Github, is rather different from the mark-up language on Trac, leaving me slightly in fumble mode :-( I have made some updates en passant, but there is still much to do updating for the much improved granularity of warning suppression and perhaps more about other code improvement tools like Lint, UBSan. The overall structure leaves a lot to be desired, but I don't want to put any more work into this without some encouragement that it will prove useful. I have posted the result of my efforts on https://github.com/boostorg/boost/wiki/Guidelines:-Warnings and I am as promised I am starting this new thread on warning for your comments, corrections, condemnations etc. HTH Paul --- Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 (0) 1539 561830

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