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Re: [boost] [scope] scope_fail is unimplementable
by Andrzej Krzemienski 14 Apr '23

14 Apr '23

niedz., 9 kwi 2023 o 03:11 Andrey Semashev via Boost <boost(a)lists.boost.org> napisał(a): > On 4/9/23 03:20, Andrzej Krzemienski wrote: > > > > Well, in my experience, the scope fail/success is exclusively about > > exceptions, so I will still focus on exceptions. > > Here is a small benchmark comparing the deactivation-based mechanism > > of a scope_guard with uncaught_exception-based mechanism of > scope_fail. > > The former performed like 36 times faster, as it doesn't have to > > perform the calls to the runtime. > > > > Sorry. Forgot the link. Here it is: > > https://quick-bench.com/q/0InBohGrnD5-soYT_GwvaCEaG74 > > <https://quick-bench.com/q/0InBohGrnD5-soYT_GwvaCEaG74> > > The thing with manually dismissing (or activating) the scope guard > before leaving the scope diminishes the usefulness of the scope guard. > The first and foremost reason to use a scope guard is to automate > execution of the action upon exiting the scope. If you now have to > manually ensure this at every point where you might leave the function, > what's the point of using it in the first place? > To "automate" is just one goal. A more modest one is to "make it manageable". Like in the case where you want to push_back into two vectors in a transactional-like fashion: vec1.push_back(Connection{params}); scope_guard pushGuard {[&]{ vec1.pop_back(); }} vec2.push_back(Storage{params}); pushGuard.deactivate(); The problem is contained, so I do not mind the call to deactivate(). But without the scope_guard, I would have to define my own class that does a pop-back in the destructor. > > Yes, you can manually (de)activate the guard in small and contained > cases, but in general I would very much prefer it to work automatically. > Otherwise, it quickly becomes a maintenance nightmare that it was > supposed to fix. > True. Therefore in my code I would contain the code that requires a guard. (In general, I prefer RAII.) But even contained cases need a scope guard. So, the trade-off is this: scope_fail: - requires no manual deactivate scope_guard with deactivate(): - works uniformly and unsurprisingly in all contexts, including coroutines - is fast. I would recommend that this trade-off is documented. Regards, &rzej; > > > Regarding failure conditions other than exceptions, the problem with > > coroutines may still appear if a thread-local storage is used, such > > as errno. > > errno is volatile (not in core C++ terms but in terms of it changing its > value in various non-obvious ways), so you would normally read its value > into a local variable immediately after a syscall for testing before > returning. It is that local variable that you check in the scope guard, > not errno itself. > > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost >

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Typo in Mysql URL on release page
by Tim Haines 14 Apr '23

14 Apr '23

The link to Mysql on the release page ( https://www.boost.org/users/history/version_1_82_0.html) points to https://www.boost.org/doc/libs/1_82_0/libs/msyql/ ^^ Thanks. - Tim

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Re: [boost] about boost::math
by Matt Borland 14 Apr '23

14 Apr '23

> a) __STDCPP_FLOAT80_T__ > With C++23 we get std::floatN_t-types, which are displayed by the macros __STDCPP_FLOATn_T__. However I miss __STDCPP_FLOAT80_T__, which has its justification/relevance. One could retrofit this > #if defined(BOOST_CSTDFLOAT_FLOAT80_NATIVE_TYPE) > #define __STDCPP_FLOAT80_T__ > namespace std > { > using float80_t = boost::float80_t; > } > #endif > Would this be useful/wanted like this? From the proposal the fixed width types are not allowed to be typedefs of the existing types https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p1467r9.html#exten…. Sections 5.3 - 5.5 also cover a whole host of conversion rules that would be unsupported. I do not believe this is something we can do at the library level. > b) complex-functions > Since C++11 there are the functions abs, asin/h, acos/h, atan/h. These are also defined in boost/math/complex.hpp. But now with 1.82 boost::math is based on C++14, which makes these manual implementations obsolete -> boost/math/complex.hpp can be removed. These functions are all explicitly marked deprecated, but we do not have a timeline for removal. > c) constexpr > I want to upgrade some functions in boost::math. How should/can I handle constexpr there? My problem is: > - in gcc almost all math functions are constexpr > - otherwise only some math functions with C++23 are constexpr > Now it would be suboptimal not to use constexpr just because it is currently not in the standard. > - If I don't define the additional functions as constexpr or stick strictly to the standard, performance might be wasted, which I don't want. > - Can I simply define the additional functions with constexpr/BOOST_CXX14_CONSTEXPR? In case of an error there will be the standard-error "not constexpr". All of the cmath functions that are specified to be constexpr in C++23 can be used with C++17 here: https://github.com/boostorg/math/tree/develop/include/boost/math/ccmath. If you would like to submit PRs for additional functions they are welcome. With the transcendental functions accuracy quickly becomes an issue: https://members.loria.fr/PZimmermann/papers/accuracy.pdf > d) implementation > In https://www.boost.org/doc/libs/1_82_0_beta1/libs/math/doc/html/math_toolkit… you describe how to implement a new math function. Is this still up to date or is it necessary for simple functions? E.g. cot -> 1/tan. That is generally correct. If this is for the implementation of constexpr cmath functions I would follow the implementations that can be found in the linked ccmath folder. Matt

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Recent videos on boost.asio from Utah C++ Programmers
by Richard 14 Apr '23

14 Apr '23

Hi Team, I sent these to boost-users, but they've been held up in moderation. It was suggested that I should also share them on this list. Cheers, -- Richard =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Subject: New video: Getting Started with Boost.Asio: Timers and Serial Ports --------- Utah Cpp Programmers has released a new video Getting Started with Boost.Asio: Timers and Serial Ports <https://www.youtube.com/watch?v=XB3uEit5R_Y> I/O operations are inherently asynchronous -- we don't know when input will arrive and when output will be generated. Network I/O can be particularly bothersome because of the long delays between sending a request and obtaining the response. Boost.Asio is a cross-platform C++ library for network and low-level I/O programming that provides developers with a consistent asynchronous model using a modern C++ approach. Boost.Asio covers timers, serial ports, files, pipes and TCP/IP networking. This month, Richard Thomson will give us an introduction to Boost.Asio concepts and asynchronous programming with this library. We'll look at how to use timers to notify our application of time passing and how to talk to serial ports asynchronously. Other Utah Cpp Programmers videos: <https://www.youtube.com/@UtahCppProgrammers> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Subject: New video on TCP/IP Networking with Boost.Asio --------- Utah C++ Programmers has released a new video TCP/IP Networking with Boost.Asio <https://www.youtube.com/watch?v=tyDWXT8-Ykc> Boost.Asio is a cross-platform C++ library for network and low-level I/O programming that provides developers with a consistent asynchronous model using a modern C++ approach. This month, Richard Thomson will continue our look at Boost.Asio with a look at TCP/IP networking. We'll look at how to implement an NNTP (Network News Transport Protocol) client using Boost.Asio. NNTP is a line-oriented protocol for reading usenet news articles. This will give us insight into all the typical issues involved in a TCP/IP networking application: - How do we resolve a host name into an IP address? - How do we establish a long-lived connection to an NNTP server? - How do we handle the arbitrarily large amounts of data from an NNTP server that arrives asynchronously? - How do we coordinate user input with NNTP I/O? - How do we handle unexpected network errors? -- "The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline> The Terminals Wiki <http://terminals-wiki.org> The Computer Graphics Museum <http://ComputerGraphicsMuseum.org> Legalize Adulthood! (my blog) <http://LegalizeAdulthood.wordpress.com>

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Re: [boost] quadmath as distinct library?
by Gero Peterhoff 14 Apr '23

14 Apr '23

Am 12.04.23 um 15:18 schrieb Christopher Kormanyos via Boost: > >>>> * problem description >>>>> In boost::math::cstdfloat AND boost::multiprecision::float128>>>> identical functions for __float128 (quadmath) are provided. >>>>> >>>>> This is unnecessary overhead. I think it would make sense>>>> to "pull out" the quadmath library as a distinct library >> Chris Kormanyos and I have discussed writing a software> implementation of binary128 that could be used cross> platform. That would be more valuable as a separate library. > It is good to read this discussion. > Historically, it all went like this... > > When we started <boost/cstdfloat.hpp>, we wereinterested in specifying floating-point types havingfixed-widths. This proposal was abandoned in the2013 timeframe, but recently picked up and broughtinto C++23 with some new stuff. > Around that time, we also "invented" Multiprecision,which came into Boost 1.53, basically with the numberbackend and cpp_dec_float only. We went on(with lots and lots of work primiarly by John) toadd several backends to Multiprecision, one ofthem being Multiprecision's float128 backend. > So indeed, we have two 128 bit floats hangingaround, yet form some platforms such as thepopular MSVC, we have zero 128-bit floatimplementations. > Writing a uniform, cross-platform implementationcombined with aliases and/or seamless use inMultiprecision is, I believe, something of interestto us all. But i believe we need some specifyingwork and a few trial implementations in order tosee how all of this should fit in together nicelain a post C++23 domain. > This is good discussion and I think we will followup on it. > Chris > > On Wednesday, April 12, 2023 at 01:12:01 PM GMT+2, Matt Borland via Boost <boost(a)lists.boost.org> wrote: > > > On Apr 11, 2023, at 8:09 PM, Gero Peterhoff via Boost <boost(a)lists.boost.org> wrote: >> >> Am 13.03.23 um 13:33 schrieb John Maddock via Boost: >> >>> On 13/03/2023 02:43, Gero Peterhoff via Boost wrote: >>> >>>> Hello, >>>> * problem description >>>> In boost::math::cstdfloat AND boost::multiprecision::float128 identical functions for __float128 (quadmath) are provided. >>>> >>>> This is unnecessary overhead. I think it would make sense to "pull out" the quadmath library as a distinct library. I did this once canonically, but it doesn't work yet because boost::math::cstdfloat/boost::multiprecision::float128 have to be adapted for this. This is a prototype where there is still a lot of work to be done. But the beginning is done. >>> >>> If you mean https://github.com/boostorg/multiprecision/blob/develop/include/boost/multi… then it's a trivially small header, and spinning stuff out into a separate library has a significant maintenance overhead. >> >> I mean this canonically. >> Advantages: >> - For both compilers (gcc/intel) the functions/limits can be provided directly, without the mass #define/#undef function-macros. >> - Clean separation and/or Konsolidierugn of the __float128 types: >> a) gcc: __float128 > > GCC also provides support for __ibm128 on PowerPC platforms. We don’t have any support for it because there has been no demand signal. > >> b) intel: Windows _Qaud -> __float128, !Windows -> __float128 (https://community.intel.com/t5/Intel-C-Compiler/C-Compiler-128-bit-floating…) >> So there is only one type __float128. >> - Clean/mature standard functions can be provided for IO. > >> Disadvantages: >> - One-time(!) effort to update dependent libs. > > Boost.Multiprecision is already available without the rest of Boost: https://github.com/boostorg/multiprecision/releases so there isn’t much bloat in the way it can be consumed now. Chris Kormanyos and I have discussed writing a software implementation of binary128 that could be used cross platform. That would be more valuable as a separate library. > > Matt Hi Matt, Hi Chris, Thanks for your comments. However, I didn't want this to be that elaborate, I just wanted to define a unique C++ interface for __float128. Right now, IO functions are spread across different header files with divergent functionality, for example: 1) boost/math/cstdfloat/cstdfloat_cmath.hpp: non-template operator<< 2) boost/math/cstdfloat/cstdfloat_iostream.hpp: operator<< operator>> 3) There are quite a few forward declarations/defines in boost/multiprecision/float128.hpp, although they are available in boost/math/cstdfloat/cstdfloat_cmath.hpp. Also, float128_backend::str seems to support std::hexfloat, which 1+2 do not. Therefore it would make sense to provide quadmath for __float128 (or intel _Quad) as a sub-library of boost.math to unify this and provide more functions (e.g. C++17 from_chars/to_chars, to_w/string). boost/multiprecision/float128.hpp could then simply use this (#include <boost/math/quadmath.hpp>). I've started with this before (see attachment); for gcc it's halfway ok, intel doesn't work. cu Gero

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Re: [boost] [scope] Proposing Boost.Scope
by Andrzej Krzemienski 14 Apr '23

14 Apr '23

czw., 13 kwi 2023 o 10:43 Andrey Semashev via Boost <boost(a)lists.boost.org> napisał(a): > On 4/13/23 06:08, Darrell Wright via Boost wrote: > > One thing I learned in my own replacement is that exit_success is > heavily penalized on MSVC, even when there is no possible exception, > because of the call to uncaught_exceptions that isn’t optimized. It’s a > good thing to document, if not already, as it is surprising. > > Well, a certain amount of overhead is expected, since the added > condition is there and not likely to be optimized away. However, I would > expect uncaught_exceptions() to be cheap, as it should simply read an > integer from TLS. It looks like the call to std::uncaught_exceptions() is not optimized out, even in -O3: https://godbolt.org/z/PYEjP5PYY > I wonder how std::uncaught_exceptions() compares to > our custom implementation in boost::core::uncaught_exceptions(). > Perhaps, I should benchmark it. > > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost >

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Master branch is NOT yet open
by Marshall Clow 14 Apr '23

14 Apr '23

I have some more work to do to start the 1.83.0 release cycle. I will post here when the master branch is open (sometime tomorrow) Thank you for your patience. — Marshall

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[release] Boost 1.82.0
by Marshall Clow 14 Apr '23

14 Apr '23

Release 1.82.0 of the Boost C++ Libraries is now available. These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. This release contain numerous enhancements and bug fixes for existing libraries. For details, including download links, see <http://www.boost.org/users/news/version_1.82.0> You can also download directly from: <https://boostorg.jfrog.io/artifactory/main/release/1.82.0/> To install this release on your system, see <http://www.boost.org/doc/libs/release/more/getting_started/index.html> Thanks to everyone who participated in this release. -- The Boost Release Team Marshall Clow, Glen Fernandes

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Re: [boost] Reducing dependency on Boost.Regex
by Andrey Semashev 13 Apr '23

13 Apr '23

On 4/13/23 06:07, Francois Kritzinger via Boost wrote: > On 2023/03/13 14:07, Andrey Semashev via Boost wrote: >> On 3/13/23 15:00, Boris Kolpackov via Boost wrote: >>> A quick note on our experience reducing dependency on Boost.Regex >>> (and thus ICU) in build2 packages for Boost 1.81.0. Now only the >>> following (leaf) libraries unconditionally depend on Boost.Regex: >>> >>> * Boost.Convert >>> * Boost.DLL >>> * Boost.Log >> >> Boost.Log can be configured to use std::regex or Boost.Xpressive as an >> alternative to Boost.Regex. > > However Boost.Log also depends on Boost.Spirit which depends on > Boost.Regex so that's a hard dependency. To my knowledge, Boost.Log doesn't use the bits of Boost.Spirit that use Boost.Regex. This means, if you build Boost.Log that uses e.g. std::regex internally, it will not link with Boost.Regex.

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Re: [boost] [scope] Proposing Boost.Scope
by Andrey Semashev 13 Apr '23

13 Apr '23

On 4/13/23 06:08, Darrell Wright via Boost wrote: > One thing I learned in my own replacement is that exit_success is heavily penalized on MSVC, even when there is no possible exception, because of the call to uncaught_exceptions that isn’t optimized. It’s a good thing to document, if not already, as it is surprising. Well, a certain amount of overhead is expected, since the added condition is there and not likely to be optimized away. However, I would expect uncaught_exceptions() to be cheap, as it should simply read an integer from TLS. I wonder how std::uncaught_exceptions() compares to our custom implementation in boost::core::uncaught_exceptions(). Perhaps, I should benchmark it.

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