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new macros
by Gero Peterhoff 28 Sep '20

28 Sep '20

Hello Developer, can you please provide these 2 macros: - BOOST_HAS_LIB_INT128 - BOOST_NO_INT8_T and there is another bug in boost::is_unsigned with char8_t. See https://godbolt.org/z/o8z1aq thx Gero

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[review][JSON] json::value as a vocabulary type
by Andrzej Krzemienski 26 Sep '20

26 Sep '20

Hi Everyone, I have heard this claim a number of times: json::value is suitable for a vocabulary type. I am not sure what that actually means: no templates? Guarantee that layout or mangled symbol will never change? Anything else? My understanding of a "vocabulary type" is that it should be usable (not necessarily with maximum efficiency) for *any* usage. In the case of JSON that would mean that I should be able to represent any value that corresponds to a valid JSON when converted to text. I do not think that json::value can claim that without the ability to serialize arbitrarily big numbers. I understand that the goal of the library is to address the most common cases, and big numbers do not fall into this category. I am just saying that the name "vocabulary type" may not be accurate here. Regards, &rzej;

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Changing virtual memory amount in Appveyor and Travis CI tests
by Edward Diener 25 Sep '20

25 Sep '20

Is it possible through .yml file for Appveyor and Travis CI to change the amount of virtual memory when running a CI test. I am running CI tests for Boost PP which heavily use the preprocessor, and some of the extended tests I am running fail on both Appveyor and Travis CI with out of memory conditions while on my own local computer, with about 32 GB of ram, the tests succeed. I think in the real world most users now have at least 32 GB of ram or more, while these virtual environments in Appveyor and/or Travis CI probably run their tests with much less overall virtual memory than an average user would have.

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Re: [boost] Endorsement, review manager sought for Boost.Describe
by Peter Dimov 24 Sep '20

24 Sep '20

> Vinícius dos Santos Oliveira wrore: > > Hi Peter, > > > > could you consider using "compile-time strings" such as Hana's? I don't > > have much use for a const char* in TMP algorithms. > > The descriptor strings are "compile-time". This, for instance, works. ... Here's how you can get a Hana string: #include <boost/describe.hpp> #include <boost/mp11.hpp> #include <boost/hana.hpp> #include <cstddef> using namespace boost::describe; using namespace boost::mp11; enum E { v1 }; BOOST_DESCRIBE_ENUM(E, v1) constexpr std::size_t strlen_( char const * s ) { std::size_t n = 0; while( *s++ ) ++n; return n; } template<class D, std::size_t... I> constexpr auto to_string_impl( index_sequence<I...> ) { return boost::hana::string_c<D::name[I]...>; } template<class D> constexpr auto to_string() { return to_string_impl<D>( make_index_sequence<strlen_(D::name)>() ); } using D = mp_first< describe_enumerators<E> >; constexpr auto st = to_string<D>(); #include <typeinfo> #include <cstdio> int main() { std::printf( "%s\n", typeid(st).name() ); }

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Endorsement, review manager sought for Boost.Describe
by Peter Dimov 24 Sep '20

24 Sep '20

I would like to submit a C++14 reflection library, Describe, to Boost and I'm looking for endorsements and a review manager. The library is at https://github.com/pdimov/describe and the documentation is at https://pdimov.github.io/describe/doc/html/describe.html. Some examples of what the library enables are given at https://pdimov.github.io/describe/doc/html/describe.html#examples. The purpose of Describe is to establish a standard way of annotating (describing) user-defined types (enums, structs and classes), so that types can be described once, and then their descriptions can be used from other libraries. At the moment, the practice is for each library to invent its own ad-hoc annotation/description mechanism.

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[nowide] cxx11_moveable_fstreams target
by Sean Farrow 24 Sep '20

24 Sep '20

Hi All, By way of context to the following query, I am trying to update the VCPKG boost port to v1.74. I noticed that the nowide library now has a jam file that has the following import statement: import ../../config/checks/config : requires ; Due to the way VCPKG works, I'm copying the config directory to where it is expected and then changing the import statement. But I then get a message that it can't find the cxx11_moveable_fstreams target. Does the nowide build process rely on any other parts of boost config? If not, where is the cxx11_moveable_fstreams defined? I should say that I'm new to the boost build system, so any help is apreciated. Thanks, Sean.

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[review][JSON] The library name...
by Andrzej Krzemienski 24 Sep '20

24 Sep '20

Hi Everyone, Looking at the reviews of Boost.JSON, a number of them fall into a distinctive pattern: reviewers are saying "you did not implement important parts of JSON parsing/serializing", and the authors' reply is "this was not the design goal". My hypothesis is that this is caused by the library name. Simple "Boost.JSON" makes a promise (at least I read it this way) "this is Boost's response to JSON-related problems". And the library does not fulfil that promise. In a sense, the name misguides the potential users who need an answer, sometimes in less than 10 seconds, to the question, "is this library going to address my need?". Maybe the library would encounter a wider consensus if it was called Boost.JSON_Value, or Boost.JSON_DOM. And if the first introductory sentence in the documentation read, "this library provides a type with Regular interface that can represent JSON contents, and provides a convenient way to serialize and then deserialize it fast and possibly in chunks." Alternatively, maybe we can consider the reviewed library as a candidate for a sub-library in a more general module of JSON. Much like Boost.Math aggregates a number of math-related components, we could treat this library as one of a number of components in a more general Boost.JSON_Toolkit library. Regards, &rzej;

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Proposal for adding C++ level to the meta/libraries.json
by Edward Diener 24 Sep '20

24 Sep '20

Since we are reviewing Vinnie Falco's JSON library I thought that this would be a good time to present a proposal to add information to each Boost library's meta/libraries.json file regarding the level of C++ standard compliance for that library. This could then be added to each library's visual documentation so that end-users would instantly know the C++ standard level they would need to use in order to use a Boost library. My proposal is to add 3 fields whose data would be the same as the cxxstd allowed values from Boost Build, using the first value of each choice ( currently 03, 11, 14, 17, 20 ). standard = minimum C++ level for the library extended = same functionality in the library as the minimum C++ level but with extended use given higher C++ levels required = new functionality in the library above the minimum C++ level which requires given higher C++ levels The 'standard' field would be a single value, while the 'extended' or 'required' fields could be more than one comma separated value. If you don't like the names for 'standard', 'extended', or 'required' you can bikeshed the name, although I think the 'standard' name is pretty well apparent. The idea is to provide this information in the meta/libraries.json field for each library, so that the end-user of the library can immediately know the usability of the library with appropriate C++ standard levels of compilation. I realize that the line between the 'extended' and 'required' entries, as I have described them, could be blurred. The 'standard' field remains the most important. I have long felt that the end-user should not have to do any investigation, in code or in documentation, just to determine if a library is usable for his C++ standard level of compilation.

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[review][JSON] Ruthgers' review
by Ruthger Dijt 23 Sep '20

23 Sep '20

> Do you think the library should be accepted as a Boost library? It will be a good addition to Boost if this library gets ACCEPTed > What is your evaluation of the design? It works, is straightforward and the interface feels good to use, the only pitfall is getting the right type you want; number_cast took me a second to realize it existed and the custom string class is something the will most likely be converted alot to std::string in an average users' code. > What is your evaluation of the implementation? As a casual user I cannot comment on this, but as I used it in stand alone / header only mode without problem I feel that i should be alright under the hood > What is your evaluation of the documentation? Could be better, especially in the examples department; it could use how-to basics > What is your evaluation of the potential usefulness of the library? Very useful > Did you try to use the library? With what compiler? Did you have any > problems? I have implemented it in a real project where RapidJSON was used before. No real problems found aside from getting exceptions because .as_double() is not able to get a technically integer from the json (which happens in user configs, example: { "test": 20 }) but that quickly resolved itself with number_cast, Ideally any number should be able to become a double in my opinion. Clang 10.0.1 was used. > How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? As stated above implemented in one project which took about an hour. > Are you knowledgeable about the problem domain? No, this review is coming from a pure casual user kindly, Ruthger Dijt

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[json][review] JSON review
by Harshada Wighe 23 Sep '20

23 Sep '20

We vote to reject the JSON library from Boost and our review of the library and reason for rejection are below: DOCUMENTATION The documentation is very good. The usage and examples and reference are easy to understand and contain all the information we are looking for. IMPLEMENTATION The organization of source code is very messy: 1. Some files do not include all headers at the very start of the file but have some include statements at the end. For example the json/object.hpp file has 10 include statements at the start of the file before the opening namespace and then 1 include statement at the end of the file after the closing namespace. This is very confusing and not a good practice. 2. Splitting the files into HPP and IPP is also not good because it spreads the class into more files than necessary and causes compilation to be slower. Using the library in a project has a complication: 3. The library is complicated to use in a project because you cannot simply include headers in any file you want. You have to include a src.hpp file but this file must be included only once. Normal header libraries in Boost just let you include the headers without this strange requirement. The library adds a lot of size to your executable: 4. Unlike other JSON libraries which are smaller, this adds several KB to the exe size. This is possibly because of use of templates or because it contains very big lookup tables. The performance is not as fast for all use cases: 5. Compared to our in house JSON library, this library was slightly slower. We have very simple but very large JSON data. We use objects and arrays, but only integer numbers with no fractional part and very large ASCII strings, and no booleans and no nulls. In one of our standalone conversion tools we tried using this library and found it had a 4% longer runtime on a small 170 MB file. The parser allocates too much memory: 6. I think this is because the design is not optimized for the case when all the JSON content is already stored in memory. In our parser we point to the strings in the original buffer. The library duplicate code that is in the C++ compiler libraries: 7. In json/config.hpp there are implementations of move and remove_cv from the C++ standard. This introduces more duplicate of this functionality into programs. Besides these points the implementation is well written. DESIGN The allocator design is not standard: 1. The library has a different allocation system that is not the C++ standard system for allocators. We did not understand why storage_ptr was needed at first. It would be better for the library to just template on allocator just like the vector class in the C++ standard. The allocator system also uses virtual calls. The C++ standard vector class also does not have this problem when it uses the standard allocator system. Other than these points the design is ok. OVERALL We would not use this library because it does not offer anything special for JSON that we need. It also uses some designs that are not standard practice. We use JSON heavily in our historical market quote service and most of our tools deal with JSON files and we use many Boost libraries so we are hoping for a JSON library in Boost that we could use instead of having our own.

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