February 2023 - Boost-users

Format a JSON string
by Markus Pieper 13 Apr '23

13 Apr '23

Hi there, I convert a std::vector<std::vector<float>> to a JSON string. Basically it works, but the format is scientific: "[[1.017E3,1.017E3,1.017E3 ... ]]" My method looks now like this: std::string Class::convertFieldAsJSON(std::vector<std::vector<float>> field) { return boost::json::serialize(boost::json::value_from(field)); } It works, but my colleagues want to see a 1017 and not 1.017E3 in the output. Is there a way to format the string? Thanks in advance, Markus

4 3

Boost Libraries and Dropping C++ Language Support
by Glen Fernandes 23 Feb '23

23 Feb '23

*Boost library authors and maintainers are free to drop support for old C++ standards in their libraries, at any time. * This includes libraries that other Boost libraries depend on. It even includes core libraries like Boost.Core or Boost.Static_Assert. We ask that maintainers do the right thing by all our users (which may include other Boost libraries) by announcing a future breakage *at least two Boost releases in advance*. When that eventual release time arrives, if Boost libraries are broken in older standards modes due to another Boost library dropping support, it will not block the Boost release. This means that we do not need to announce "Boost is dropping C++03" because Boost doesn't "support C++03" now as it is. It means that you, maintainer of Boost.X, should realize that you are free to announce that "Boost.X is dropping C++XY in version 1.Z" as you see fit. Boost in its infancy thrived because its libraries were on the cutting edge. Boost libraries today should similarly not be confined simply because other Boost libraries have chosen to depend on them. Furthermore, as Boost release managers we support authors exercising this freedom, and do not intend to impose any restrictions on what language support they must maintain. We will add a page to the Boost website stating the above formally. -- The release team (Glen Fernandes, Marshall Clow)

2 1

[iostreams] When plan to move to C++20
by Seyyed Soroosh Hosseinalipour 17 Feb '23

17 Feb '23

ITNOA I have question about the plan to migrate code base from C++03 to C++20 for iostreams library I think iostreams library have very more clean if using modern C++ features, such as Concept Did you have any plan about that? thanks

4 5

Abwesenheitsnachricht: Re: [iostreams] When plan to move to C++20
by Sören Textor 17 Feb '23

17 Feb '23

Derzeit bin ich nicht im Hause Ihre E-Mail wird nicht weitergeleitet. In dringenden Fällen bitte support(a)ditec-gmbh.de oder Telefonhotline +49-6221-31698-110 oder die Zentrale +49-6221-31698-0 kontaktieren. Mit freundlichen Grüßen Dr. Sören Textor ----------------------------------------------- DiTEC Dr. Siegfried Kahlich & Dierk Langer GmbH Im Breitspiel 19 | 69126 Heidelberg | Germany Handelsregister | Mannheim | HRB 341229 Dieses Dokument ist vertraulich zu behandeln. Die Weitergabe, sowie Vervielfältigung, Verwertung und Mitteilung seines Inhalts ist nur mit unserer ausdrücklichen Genehmigung gestattet. Alle Rechte vorbehalten, insbesondere für den Fall der Schutzrechtsanmeldung. This document has to be treated confidentially. Its contents are not to be passed on, duplicated, exploited or disclosed without our express permission. All rights reserved, especially the right to apply for protective rights.

1 0

boost serialization of non-POD 16bit float : Half
by Nicholas Yue 17 Feb '23

17 Feb '23

Hi, I am trying to serialize out the value of OpenEXR's Half type values. I came across mention that custom types requires something like the following ``` namespace boost { namespace serialization { template<class Archive> void serialize(Archive & ar, half & h, const unsigned int version) { ar & boost::serialization::make_nvp("value", h); } } // namespace serialization } // namespace boost ``` The code compiles but when I run it, it segfaults. Is boost serializer a suitable for such use case ? Cheers -- Nicholas Yue https://www.linkedin.com/in/nicholasyue/

1 0

Unable to compile when using BOOST_DETAIL_SPINLOCK_INIT
by radiatejava 09 Feb '23

09 Feb '23

I have an existing code for an application that uses BOOST_DETAIL_SPINLOCK_INIT from boost/smart_ptr/detail/spinlock.hpp. It is all fine when using with boost ver 1.53. I am trying to migrate to boost ver 1.66 and now this compilation fails. To isolate the issue, I have a sample program: #include <iostream> #include <boost/smart_ptr/detail/spinlock.hpp> class BoostTest { public: BoostTest(int v): val(v), bLock(BOOST_DETAIL_SPINLOCK_INIT) { std::cout << "constructor called" << std::endl; } int getValue() { std::cout << "getValue() called" << std::endl; return val; } private: int val; boost::detail::spinlock bLock; }; int main() { std::cout << "starting test" << std::endl; BoostTest bt(10); std::cout << "value now " << bt.getValue() << std::endl; } With ver 1.66, it now gives me the error. Why this error after upgrade to 1.66? How do I correct it? $ g++ -std=c++11 -I/data/hdd/code/mgmt/common/external/boost/ifc/dist/include -c boosttest.cc boosttest.cc: In constructor 'BoostTest::BoostTest(int)': boosttest.cc:6:63: error: use of deleted function 'boost::detail::spinlock::spinlock(boost::detail::spinlock&&)' BoostTest(int v): val(v), bLock(BOOST_DETAIL_SPINLOCK_INIT) { ^ In file included from /data/hdd/code/mgmt/common/external/boost/ifc/dist/include/boost/smart_ptr/detail/spinlock.hpp:47:0, from boosttest.cc:2: /data/hdd/code/mgmt/common/external/boost/ifc/dist/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp:27:7: note: 'boost::detail::spinlock::spinlock(boost::detail::spinlock&&)' is implicitly deleted because the default definition would be ill-formed: class spinlock ^ /data/hdd/code/mgmt/common/external/boost/ifc/dist/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp:27:7: error: use of deleted function 'std::atomic_flag::atomic_flag(const std::atomic_flag&)' In file included from /usr/include/c++/4.8/atomic:41:0, from /data/hdd/code/mgmt/common/external/boost/ifc/dist/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp:19, from /data/hdd/code/mgmt/common/external/boost/ifc/dist/include/boost/smart_ptr/detail/spinlock.hpp:47, from boosttest.cc:2: /usr/include/c++/4.8/bits/atomic_base.h:275:5: error: declared here atomic_flag(const atomic_flag&) = delete; ^

2 1

boost::process : write both stdout and stderr to the same stream ?
by Nicholas Yue 02 Feb '23

02 Feb '23

Hi, Is it possible to write both the stdout and stderr stream to the same output file/stream ? I am hoping to emulate ``` bp_stdout_stderr_app > output.txt 2>&1 ``` I tried doing something like that but get a runtime error Run output ``` terminate called after throwing an instance of 'boost::process::process_error' what(): dup3() failed: Bad file descriptor stdout : 000 stdout : 020 stdout : 040 Aborted (core dumped) ``` Source code ``` #include <boost/process.hpp> #include <iostream> using namespace boost::process; int main() { ipstream pipe_stream; child c("bp_stdout_stderr_app", std_out > pipe_stream, std_err > pipe_stream); std::string line; while (pipe_stream && std::getline(pipe_stream, line) && !line.empty()) std::cerr << line << std::endl; c.wait(); } ``` Cheers -- Nicholas Yue https://www.linkedin.com/in/nicholasyue/

1 0