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A Newbie Boost.Build with Variants Question
by Ryan Heniser 24 Oct '20

24 Oct '20

Hi, I am building Boost 1.61 (we need this old version for other libraries) for the first time at work with Boost.Build (b2). I have successfully built Boost (using b2) for gcc 4.8. If I want to add one or more variants (for example using gcc 6.3), where should I put the Boost header’s include directory? Should one go inside each variant or should just one go at the root directory containing the variant directories? Kind regards, Ryan

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[Newbie][Intrusive] - Beginners question
by Gaier, Bjoern 22 Oct '20

22 Oct '20

Hey everybody, I looked into the boost intrusive container and played around with it a bit. I tried the following code: struct animal : public boost::intrusive::list_base_hook<> { std::string name; int legs; animal(std::string n, int l) : name{std::move(n)}, legs{l} {} }; int main(int argc, char **argv) { std::vector<animal> test; boost::intrusive::list<animal> wuff; for(int n = 0; n < 5; n++) { test.push_back(animal("Katze", 4)); } for(int n = 0; n < 5; n++) { wuff.push_back(test[n]); } for(int n = 0; n < 15; n++) { wuff.push_back(test[n]); } for(auto elem : wuff) { printf("%s\n", elem.name.c_str()); } } This code does crash! I guess this is because "test" relocated the memory and therefor "wuff" lost its references. I would expect the same result if I would have a std::list with pointers to animal structures - this is why I wonder what the benefit of an intrusive container is compared to the same container with just pointers in it. Hope someone can explain me this! Thank you in advance and kind greetings Björn Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.

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Does boost promise/future support corroutines?
by David Frank 19 Oct '20

19 Oct '20

Hi, Does boost promise/future support coroutines? For example, the get call only block the running coroutine, instead of the whole thread? Thanks,David

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Boost.MSM: Problem with defered events
by Georg Gast 16 Oct '20

16 Oct '20

Dear Boost users, i am currently writing a driver for the ADS1256 chip with Boost.MSM. Yes, there are other drivers. I do this for training and fun. During the startup phase i need to defer the requests from the user as the SPI bus is not yet available. To model the behaviour the most correct, i tried to model it with MSM. In the transition table, i use the "Defer" action to defer these events. In my Idle state, after the startup phase, there is a transition with this defered event going to the "work" states. In the debugger i can see, that the defered_event_queue holds one defered event and it is of my type but it is not processed. I did use boost 1.67.0 (from debian buster ) and also 1.74.0 (self compiled) to test this. My program can be also compiled under Windows and VS2019 as i handled the hardware interfacing with a abstract class. It works under Windows and 1.74.0. With VS2017 and 1.67.0 it also does not work. Under Linux and gcc it always stops at the Idle state where i wait for the defered event. At the end is my transition table. Any ideas are welcome! Georg // clang-format off struct transition_table : mpl::vector< // +----------------+-------------------+----------------+---------------------------+----------------------+ // Region 0 // +----------------+-------------------+----------------+---------------------------+----------------------+ // Start Event Next Action Guard // +----------------+-------------------+----------------+---------------------------+----------------------+ Row < NotIntialized , ev_Init , WaitDRDYID , none , none >, Row < WaitDRDYID , ev_CheckFlags , ReadID , none , IsDrdy0 >, Row < ReadID , ev_CheckFlags , none , none , none >, Row < ReadID , Spi::Reply , ReadIDFailed , none , IsIDNotOk >, Row < ReadID , Spi::Reply , Idle , none , IsIDOk >, // during the startup phase these event must be defered Row < NotIntialized , ev_MultiStart , none , Defer , none >, Row < WaitDRDYID , ev_MultiStart , none , Defer , none >, Row < ReadID , ev_MultiStart , none , Defer , none >, // +----------------+-------------------+----------------+---------------------------+----------------------+ Row < Idle , ev_CheckFlags , none , none , none >, Row < Idle , ev_MultiStart , MConfigWaitDRDY, none , none >, // +----------------+-------------------+----------------+---------------------------+----------------------+ Row < MConfigWaitDRDY, ev_CheckFlags , MSwitchConfig , none , IsDrdy0 >, Row < MSwitchConfig , ev_CheckFlags , none , none , none >, Row < MSwitchConfig , Spi::Reply , MMuxWaitDRDY , none , IsECNotFailed >, Row < MMuxWaitDRDY , ev_CheckFlags , MSwitchMux , none , IsDrdy0 >, Row < MSwitchMux , ev_CheckFlags , none , none , none >, Row < MSwitchMux , Spi::Reply , MSync , none , IsECNotFailed >, Row < MSync , Spi::Reply , MDataWaitDRDY , none , IsECNotFailed >, Row < MDataWaitDRDY , ev_CheckFlags , MReadData , none , IsDrdy0 >, Row < MReadData , ev_CheckFlags , none , none , none >, Row < MReadData , Spi::Reply , Idle , WorkDone , IsWorkDone >, Row < MReadData , Spi::Reply , MMuxWaitDRDY , RemoveDoneWork , IsStillWorkTodo >, // +----------------+-------------------+----------------+---------------------------+----------------------+ // Region 1 // +----------------+-------------------+----------------+---------------------------+----------------------+ Row < DrdyUndefined , ev_DRDY_0 , Drdy0 , none , none >, Row < DrdyUndefined , ev_DRDY_1 , Drdy1 , none , none >, Row < Drdy0 , ev_DRDY_0 , none , none , none >, Row < Drdy0 , ev_DRDY_1 , Drdy1 , none , none >, Row < Drdy1 , ev_DRDY_0 , Drdy0 , none , none >, Row < Drdy1 , ev_DRDY_1 , none , none , none >, // +----------------+-------------------+----------------+---------------------------+----------------------+ // Region 2 // +----------------+-------------------+----------------+---------------------------+----------------------+ // Start Event Next Action Guard // +----------------+-------------------+----------------+---------------------------+----------------------+ Row < AllOk , Spi::Reply , ErrorMode , none , IsECFailed > // +----------------+-------------------+----------------+---------------------------+----------------------+ > {}; // clang-format on

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[Circular Buffer] Why doesn't have “emplace” interface?
by Марсель Галимуллин 16 Oct '20

16 Oct '20

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Boost configuration for VS Code / MacOS X Catalina
by Stefano Gragnani 12 Oct '20

12 Oct '20

Hi, how should i configure vs code to use Boost? I tried to compile the following example: #include <iostream> #include <boost/multiprecision/float128.hpp> #include <boost/math/special_functions/gamma.hpp> int main() { using namespace boost::multiprecision; // Operations at 128-bit precision and full numeric_limits support: float128 b = 2; // There are 113-bits of precision: std::cout << std::numeric_limits<float128>::digits << std::endl; // Or 34 decimal places: std::cout << std::numeric_limits<float128>::digits10 << std::endl; // We can use any C++ std lib function, lets print all the digits as well: std::cout << std::setprecision(std::numeric_limits<float128>::max_digits10) << log(b) << std::endl; // print log(2) = 0.693147180559945309417232121458176575 // We can also use any function from Boost.Math: std::cout << boost::math::tgamma(b) << std::endl; // And since we have an extended exponent range we can generate some really large // numbers here (4.02387260077093773543702433923004111e+2564): std::cout << boost::math::tgamma(float128(1000)) << std::endl; // // We can declare constants using GCC or Intel's native types, and the Q suffix, // these can be declared constexpr if required: constexpr float128 pi = 3.1415926535897932384626433832795028841971693993751058Q; return 0; } but that's what I get: Executing task: g++-10 -g -std=c++17 '-fext-numeric-literals' main.cpp -L/usr/local/Cellar/gcc/10.2.0/lib/gcc/10/ -lquadmath -o main.out < main.cpp:2:10: fatal error: boost/multiprecision/float128.hpp: No such file or directory 2 | #include <boost/multiprecision/float128.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. The terminal process "/bin/zsh '-c', 'g++-10 -g -std=c++17 '-fext-numeric-literals' main.cpp -L/usr/local/Cellar/gcc/10.2.0/lib/gcc/10/ -lquadmath -o main.out'" failed to launch (exit code: 1). My task.json is: { // See https://go.microsoft.com/fwlink/?LinkId=733558 <https://go.microsoft.com/fwlink/?LinkId=733558> // for the documentation about the tasks.json format "version": "2.0.0", "tasks": [ { "label": "Build with g++ 10", "type": "shell", "command": "g++-10", "args": [ "-g", "-std=c++17", "'-fext-numeric-literals'", "main.cpp", "-L/usr/local/Cellar/gcc/10.2.0/lib/gcc/10/", "-lquadmath", "-o", "main.out" ], "group": { "kind": "build", "isDefault": true } }, { "label": "Build with Intel ICC", "type": "shell", "command": "icc", "args": [ "-g", "-std=c++17", "main.cpp", "-o", "main.out" ], "group": { "kind": "build", "isDefault": true } }, { "label": "Run Project", "type": "shell", "command": "./main.out", "group": { "kind": "build", "isDefault": true } } ] } And my c_cpp_properties.json is: { "configurations": [ { "name": "Mac", "includePath": [ "${workspaceFolder}/**", "/usr/local/Cellar/boost/1.73.0/include/**" ], "defines": [], "macFrameworkPath": [], "compilerPath": "/usr/local/bin/g++-10", "cStandard": "gnu18", "cppStandard": "gnu++14", "intelliSenseMode": "gcc-x64" } ], "version": 4 } Thanks Stefano Gragnani

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A question about boost::uuid
by Shishir Pandey 10 Oct '20

10 Oct '20

Hi all, I have been trying to figure out how to use murmurhash3 with boost::uuid. Looking at the documentation it is not entirely clear to me if a class implementing murmurhash3 that provides the interface defined by NameHashProvider would be sufficient. If yes, would creating a wrapper over the following implementation work? https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp Can anyone direct me to some similar implementation perhaps not of using murmurhash3 but of using any other algorithms? Regards, Shishir Pandey -- Necessity is not an established fact, but an interpretation. - Friedrich Wilhelm Nietzsche

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Re: [Boost-users] [Boost-announce] [PFR][review] Result
by Antony Polukhin 09 Oct '20

09 Oct '20

On Thu, Oct 8, 2020, 13:51 Benedek Thaler via Boost-announce < boost-announce(a)lists.boost.org> wrote: <...> > Benedek > review wizard > Many thanks for beeng the review manager! >

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Re: [Boost-users] [Boost-announce] [FPR] Review of FPR starts Today: Sept 28 - Oct 7
by Nat Goodspeed 05 Oct '20

05 Oct '20

On Mon, Sep 28, 2020 at 1:15 PM Benedek Thaler via Boost-announce < boost-announce(a)lists.boost.org> wrote: - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? > I have read only the announcement email, but it prompts a very interesting question: does the FPR library facilitate integration with Boost.Serialization? If not yet, how hard would it be to improve the interoperability of those two libraries? If the FPR documentation already addresses this point, a terse reply to that effect will suffice.

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improve TypeTraits
by Gero Peterhoff 04 Oct '20

04 Oct '20

Hello John, you have probably already read that I think some new TypeTraits are useful. Here are the details: a) very useful: precise type classification - this is the basis of every abstraction and should definitely be implemented - is_character: contains only characters (char32/16/8_t, wchar_t, char); is_un/signed_character - is_integer: contains only integers and no characters and no bool (u/int8..X_t); is_un/signed_integer - is_logic: contains only logical types (bool and boost::tribool, *)) - is_string: contains everything that can be used as a string, but needs these specializations: 1) is_bounded_string (similar to is_bounded_array) 2) is_unbounded_string (similar to is_unbounded_array) 3) is_static_string (for boost::basic_static_string) 4) is_string_ref (for boost::basic_string ref) 5) is_string_view (for std::basic_string_view) 6) is_string_class (for std::basic_string) - character_of: the underlying character type based on is_string b) very useful - remove_cv_ptr (similar to remove_cv_ref) - make_same_signed (similar to make_un/signed): changes the sign depending on a type - conditional_signed: changes the sign depending on a truth value - is_same_signed: same sign c) also makes sense - is_tuple - is_rational (similar to boost::is_complex) - is_binary: if base==2 (numeric_limits::radix==2) - is_decimal: if base==10 (numeric_limits::radix==10) d) - is_native: a type is natively available on the platform (e.g. int64_t: Linux32:false, Linux64:true; float80_t: x86:true, else:false) - is_vectorisable: a type can be vectorized natively on the platform - there are basic SSE/AVX/SVE/... functions However, I have a problem: boost/std::is_integral contain bool. Perhaps you can do that like this, but it leads to problems with is_arithmetic, since is_arithmetic is based on is_integral and thus contains bool. I think the point of is_arithmetic is to be able to calculate numerically with the type - so the scenarios are not useful: abs(bool), sin/cos/...(bool), etc. The same applies to characters. There are two possible solutions: - redefine is_arithmetic -> is_integer || is_floating_point - a new TypeTrait is_numeric (e.g.) -> is_integer || is_floating_point There are some differences between boost- and std-TypeTraits. Can you please include that in the documentation? Furthermore there seem to be errors with char8_t, e.g. boost::is_unsigned<char8_t> -> false, std::is_unsigned<char8_t> -> true (correct). Summary With these measures, a large number of template functions/classes can then be tailored precisely to the application and incorrect use can be prevented. regards Gero *) I've written a couple of classes for logic: bool3_t (a modern variant of boost::tribool), bool4_t (http://www.filosofia.unimi.it/dagostino/wp-content/uploads/2017/05/Belnap.p…) and bool2_t (for completeness)

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