Date: Wed, 12 Jul 2023 17:02:10 -0400
Thanks Arthur!
Le mer. 12 juil. 2023 à 15:10, Arthur O'Dwyer <arthur.j.odwyer_at_[hidden]> a
écrit :
> "Predictable lambdas": Might be pursued (under exploration). Being able to
>> declare a lambda on the stack, without initializing it right away, and
>> having access to its constructor (some sort of placement new on an
>> uninitialized lambda, kind of like an optional<lambda>)
>
>
> Two comments here:
> (1) {{citation needed}}. Every single entry in these tables will benefit
> from a third column with the URL(s) of people actually requesting these
> things. Otherwise it's very easy for me to believe that an entry has lost
> something in translation, and/or is solving an XY problem.
>
> (2) This particular entry probably has an XY problem; but if we assume we
> really do want to solve Y, then the feature request here doesn't really
> have anything to do with "lambdas." What it's really asking for is a pair
> of attributes to stick on a variable: [[no_construct]], to skip the
> constructor but still destroy the variable at end-of-scope as usual; and
> [[no_destroy]] to do the constructor but skip the destructor.
> Clang and GCC both support [[no_destroy]]
> <https://clang.llvm.org/docs/AttributeReference.html#no-destroy>, but
> only on static and thread-local storage.
> Nobody supports [[no_construct]] yet.
> But I know about these attributes because *if we had them for stack
> variables* then the vendor could implement P1144 `T std::relocate(T*)`
> without intimate knowledge
> <https://quuxplusone.github.io/blog/2022/05/18/std-relocate/> of the
> calling convention:
>
> template<class T>
> T relocate(T *src) {
> if constexpr (std::is_trivially_relocatable_v<T>) {
> [[do_not_construct]] T dst;
> std::relocate_at(src, &dst); // construct dst and destroy src, as
> if by memcpy
> return dst; // but still get the benefit of NRVO here
> } else {
> T dst = T(std::move(*src));
> std::destroy_at(src);
> return dst; // get the benefit of NRVO here
> }
> }
>
> The [[no_destroy]] attribute is probably desirable for some SG14 folks,
> too, because it lets you have a global variable like
> [[no_destroy]] const std::string kConstant = "constant";
> of a non-trivial type that requires dynamic initialization, but the
> programmer *doesn't care if its destructor runs at program exit* — that's
> just useless bookkeeping, so we would like to have a way to tell the
> compiler to omit it.
>
> –Arthur
>
> On Wed, Jul 12, 2023 at 2:39 PM Patrice Roy via SG14 <
> sg14_at_[hidden]> wrote:
>
>> As a reminder :)
>>
>> Le mar. 11 juil. 2023 à 23:34, Michael Wong via SG14 <
>> sg14_at_[hidden]> a écrit :
>>
>>> Topic: SG14 Low Latency Monthly This meeting is focused on Finance/Low
>>> Latency though we can continue with the Games paper that
>>> was started in January, depending on what other papers or topics are of
>>> interest.
>>>
>>> I am also looking for a finance Subgroup chair. Thank you.
>>>
>>> Hi,
>>>
>>> Michael Wong is inviting you to a scheduled Zoom meeting.
>>>
>>> Topic: SG14 monthly
>>> Time: 2nd Wednesdays 02:00 PM Eastern Time (US and Canada)
>>> Every month on the Second Wed,
>>>
>>> Join from PC, Mac, Linux, iOS or Android:
>>> https://iso.zoom.us/j/93151864365?pwd=aDhOcDNWd2NWdTJuT1loeXpKbTcydz09
>>> Password: 789626
>>>
>>> Or iPhone one-tap :
>>> US: +12532158782,,93151864365# or +13017158592,,93151864365#
>>> Or Telephone:
>>> Dial(for higher quality, dial a number based on your current
>>> location):
>>> US: +1 253 215 8782 or +1 301 715 8592 or +1 312 626 6799 or +1
>>> 346 248 7799 or +1 408 638 0968 or +1 646 876 9923 or +1 669 900 6833
>>> or 877 853 5247 (Toll Free)
>>> Meeting ID: 931 5186 4365
>>> Password: 789626
>>> International numbers available: https://iso.zoom.us/u/abRrVivZoD
>>>
>>> Or Skype for Business (Lync):
>>> https://iso.zoom.us/skype/93151864365
>>>
>>> Agenda:
>>>
>>> 1. Opening and introduction
>>>
>>> ISO Code of Conduct
>>> <
>>>
>>> https://isotc.iso.org/livelink/livelink?func=ll&objId=20882226&objAction=Open&nexturl=%2Flivelink%2Flivelink%3Ffunc%3Dll%26objId%3D20158641%26objAction%3Dbrowse%26viewType%3D1
>>> *>*
>>>
>>> ISO patent policy.
>>>
>>> https://isotc.iso.org/livelink/livelink/fetch/2000/2122/3770791/Common_Policy.htm?nodeid=6344764&vernum=-2
>>>
>>> IEC Code of Conduct:
>>>
>>> https://www.iec.ch/basecamp/iec-code-conduct-technical-work
>>>
>>> WG21 Code of Conduct:
>>>
>>>
>>> https://isocpp.org/std/standing-documents/sd-4-wg21-practices-and-procedures
>>>
>>> 1.1 Roll call of participants
>>>
>>> 1.2 Adopt agenda
>>>
>>> 1.3 Approve minutes from previous meeting, and approve publishing
>>> previously approved minutes to ISOCPP.org
>>>
>>> 1.4 Action items from previous meetings
>>>
>>> 2. Main issues (125 min)
>>>
>>> 2.1 General logistics
>>>
>>> Varna F2F
>>> C++23 and C++26 status
>>>
>>> Future meeting plans
>>>
>>> *Mar 8, 2023 02:00 PM ET: Embedded
>>> *Apr 12, 2023 02:00 PM ET: Cancelled
>>> * May 10, 2023 02:00 PM ET: Cancelled
>>> * June 14, 2023 02:00 PM ET: Cancelled
>>> * July 12, 2023 02:00 PM ET: Finance
>>> * Aug 9, 2023 02:00 PM ET: Games
>>> * Sep 12, 2023 02:00 PM ET: Embedded
>>> * Oct 1: CPPCON
>>> * Oct 10, 2023 02:00 PM ET: Finance
>>> *Nov 8, 2023 02:00 PM ET: Kona F2F Cancelled
>>> * Dec 12, 2023 02:00 PM ET: Games
>>>
>>> 2.2 Paper reviews
>>> Discussion on Embedded:
>>> Review latest mailings:
>>> P2532 Removing exception_ptr from the receivers concept
>>> Based on the last meeting and the discussions here.
>>> P2544 C++ Exceptions are becoming more and more problematic
>>> We might want to chime in here.
>>> /Paul
>>> P. S. P2327 de-deprecating volatile received a "consensus" straw poll.
>>>
>>>
>>> Discussion on Low Latency/Finance topics
>>>
>>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p1839r4.pdf
>>>
>>> Patrice's paper on games.
>>>
>>> P2300
>>> Swift
>>>
>>>
>>>
>>> Discussion about Games topics:
>>>
>>> P2388R1 - Minimum Contract Support: either Ignore or Check_and_abort
>>> <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2388r1.html>
>>>
>>> Patrice's WIP on Games issues.
>>>
>>> Finance topics from July 14, 2021.
>>>
>>> https://lists.isocpp.org/sg14/2021/06/0636.php
>>>
>>> https://lists.isocpp.org/sg14/2021/07/0642.php
>>>
>>> 2.2.1 any other proposal for reviews?
>>>
>>> Deterministic Exception for Embedded by James Renwick
>>>
>>> https://www.pure.ed.ac.uk/ws/portalfiles/portal/78829292/low_cost_deterministic_C_exceptions_for_embedded_systems.pdf
>>>
>>> Freestanding?
>>>
>>> SG14/SG19 features/issues/defects:
>>>
>>>
>>> https://docs.google.com/spreadsheets/d/1JnUJBO72QVURttkKr7gn0_WjP--P0vAne8JBfzbRiy0/edit#gid=0
>>>
>>> 2.3 Domain-specific discussions
>>>
>>> 2.3.1 SIG chairs
>>>
>>> - Embedded Programming chairs: Ben Craig, Wouter van Ooijen and Odin
>>> Holmes, John McFarlane
>>>
>>> - Financial/Trading chairs: Staffan TjernstrÃm
>>> Carl Cooke, Neal Horlock,
>>> - Games chairs: Rene Riviera, Guy Davidson and Paul Hampson, Patrice
>>> Roy
>>>
>>> - Linear Algebra chairs: Bob Steagall, Mark Hoemmen, Guy Davidson
>>>
>>> 2.4 Other Papers and proposals
>>>
>>> 2.5 Future F2F meetings:
>>>
>>> 2.6 future C++ Standard meetings:
>>> https://isocpp.org/std/meetings-and-participation/upcoming-meetings
>>>
>>> -
>>>
>>> 3. Any other business
>>> Reflector
>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>>> As well as look through papers marked "SG14" in recent standards
>>> committee
>>> paper mailings:
>>> http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/
>>> http://open-std.org/jtc1/sc22/wg21/docs/papers/2016/
>>>
>>> Code and proposal Staging area
>>> https://github.com/WG21-SG14/SG14
>>> 4. Review
>>>
>>> 4.1 Review and approve resolutions and issues [e.g., changes to SG's
>>> working draft]
>>>
>>> 4.2 Review action items (5 min)
>>>
>>> 5. Closing process
>>>
>>> 5.1 Establish next agenda
>>>
>>> 5.2 Future meeting
>>>
>>>
>>> *Mar 8, 2023 02:00 PM ET: Embedded
>>> *Apr 12, 2023 02:00 PM ET: Cancelled
>>> * May 10, 2023 02:00 PM ET: Cancelled
>>> * June 14, 2023 02:00 PM ET: Cancelled
>>> * July 12, 2023 02:00 PM ET: Finance
>>> * Aug 9, 2023 02:00 PM ET: Games
>>> * Sep 12, 2023 02:00 PM ET: Embedded
>>> * Oct 1: CPPCON
>>> * Oct 10, 2023 02:00 PM ET: Finance
>>> *Nov 8, 2023 02:00 PM ET: Kona F2F Cancelled
>>> * Dec 12, 2023 02:00 PM ET: Games
>>> _______________________________________________
>>> SG14 mailing list
>>> SG14_at_[hidden]
>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>>>
>> _______________________________________________
>> SG14 mailing list
>> SG14_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>>
>
Le mer. 12 juil. 2023 à 15:10, Arthur O'Dwyer <arthur.j.odwyer_at_[hidden]> a
écrit :
> "Predictable lambdas": Might be pursued (under exploration). Being able to
>> declare a lambda on the stack, without initializing it right away, and
>> having access to its constructor (some sort of placement new on an
>> uninitialized lambda, kind of like an optional<lambda>)
>
>
> Two comments here:
> (1) {{citation needed}}. Every single entry in these tables will benefit
> from a third column with the URL(s) of people actually requesting these
> things. Otherwise it's very easy for me to believe that an entry has lost
> something in translation, and/or is solving an XY problem.
>
> (2) This particular entry probably has an XY problem; but if we assume we
> really do want to solve Y, then the feature request here doesn't really
> have anything to do with "lambdas." What it's really asking for is a pair
> of attributes to stick on a variable: [[no_construct]], to skip the
> constructor but still destroy the variable at end-of-scope as usual; and
> [[no_destroy]] to do the constructor but skip the destructor.
> Clang and GCC both support [[no_destroy]]
> <https://clang.llvm.org/docs/AttributeReference.html#no-destroy>, but
> only on static and thread-local storage.
> Nobody supports [[no_construct]] yet.
> But I know about these attributes because *if we had them for stack
> variables* then the vendor could implement P1144 `T std::relocate(T*)`
> without intimate knowledge
> <https://quuxplusone.github.io/blog/2022/05/18/std-relocate/> of the
> calling convention:
>
> template<class T>
> T relocate(T *src) {
> if constexpr (std::is_trivially_relocatable_v<T>) {
> [[do_not_construct]] T dst;
> std::relocate_at(src, &dst); // construct dst and destroy src, as
> if by memcpy
> return dst; // but still get the benefit of NRVO here
> } else {
> T dst = T(std::move(*src));
> std::destroy_at(src);
> return dst; // get the benefit of NRVO here
> }
> }
>
> The [[no_destroy]] attribute is probably desirable for some SG14 folks,
> too, because it lets you have a global variable like
> [[no_destroy]] const std::string kConstant = "constant";
> of a non-trivial type that requires dynamic initialization, but the
> programmer *doesn't care if its destructor runs at program exit* — that's
> just useless bookkeeping, so we would like to have a way to tell the
> compiler to omit it.
>
> –Arthur
>
> On Wed, Jul 12, 2023 at 2:39 PM Patrice Roy via SG14 <
> sg14_at_[hidden]> wrote:
>
>> As a reminder :)
>>
>> Le mar. 11 juil. 2023 à 23:34, Michael Wong via SG14 <
>> sg14_at_[hidden]> a écrit :
>>
>>> Topic: SG14 Low Latency Monthly This meeting is focused on Finance/Low
>>> Latency though we can continue with the Games paper that
>>> was started in January, depending on what other papers or topics are of
>>> interest.
>>>
>>> I am also looking for a finance Subgroup chair. Thank you.
>>>
>>> Hi,
>>>
>>> Michael Wong is inviting you to a scheduled Zoom meeting.
>>>
>>> Topic: SG14 monthly
>>> Time: 2nd Wednesdays 02:00 PM Eastern Time (US and Canada)
>>> Every month on the Second Wed,
>>>
>>> Join from PC, Mac, Linux, iOS or Android:
>>> https://iso.zoom.us/j/93151864365?pwd=aDhOcDNWd2NWdTJuT1loeXpKbTcydz09
>>> Password: 789626
>>>
>>> Or iPhone one-tap :
>>> US: +12532158782,,93151864365# or +13017158592,,93151864365#
>>> Or Telephone:
>>> Dial(for higher quality, dial a number based on your current
>>> location):
>>> US: +1 253 215 8782 or +1 301 715 8592 or +1 312 626 6799 or +1
>>> 346 248 7799 or +1 408 638 0968 or +1 646 876 9923 or +1 669 900 6833
>>> or 877 853 5247 (Toll Free)
>>> Meeting ID: 931 5186 4365
>>> Password: 789626
>>> International numbers available: https://iso.zoom.us/u/abRrVivZoD
>>>
>>> Or Skype for Business (Lync):
>>> https://iso.zoom.us/skype/93151864365
>>>
>>> Agenda:
>>>
>>> 1. Opening and introduction
>>>
>>> ISO Code of Conduct
>>> <
>>>
>>> https://isotc.iso.org/livelink/livelink?func=ll&objId=20882226&objAction=Open&nexturl=%2Flivelink%2Flivelink%3Ffunc%3Dll%26objId%3D20158641%26objAction%3Dbrowse%26viewType%3D1
>>> *>*
>>>
>>> ISO patent policy.
>>>
>>> https://isotc.iso.org/livelink/livelink/fetch/2000/2122/3770791/Common_Policy.htm?nodeid=6344764&vernum=-2
>>>
>>> IEC Code of Conduct:
>>>
>>> https://www.iec.ch/basecamp/iec-code-conduct-technical-work
>>>
>>> WG21 Code of Conduct:
>>>
>>>
>>> https://isocpp.org/std/standing-documents/sd-4-wg21-practices-and-procedures
>>>
>>> 1.1 Roll call of participants
>>>
>>> 1.2 Adopt agenda
>>>
>>> 1.3 Approve minutes from previous meeting, and approve publishing
>>> previously approved minutes to ISOCPP.org
>>>
>>> 1.4 Action items from previous meetings
>>>
>>> 2. Main issues (125 min)
>>>
>>> 2.1 General logistics
>>>
>>> Varna F2F
>>> C++23 and C++26 status
>>>
>>> Future meeting plans
>>>
>>> *Mar 8, 2023 02:00 PM ET: Embedded
>>> *Apr 12, 2023 02:00 PM ET: Cancelled
>>> * May 10, 2023 02:00 PM ET: Cancelled
>>> * June 14, 2023 02:00 PM ET: Cancelled
>>> * July 12, 2023 02:00 PM ET: Finance
>>> * Aug 9, 2023 02:00 PM ET: Games
>>> * Sep 12, 2023 02:00 PM ET: Embedded
>>> * Oct 1: CPPCON
>>> * Oct 10, 2023 02:00 PM ET: Finance
>>> *Nov 8, 2023 02:00 PM ET: Kona F2F Cancelled
>>> * Dec 12, 2023 02:00 PM ET: Games
>>>
>>> 2.2 Paper reviews
>>> Discussion on Embedded:
>>> Review latest mailings:
>>> P2532 Removing exception_ptr from the receivers concept
>>> Based on the last meeting and the discussions here.
>>> P2544 C++ Exceptions are becoming more and more problematic
>>> We might want to chime in here.
>>> /Paul
>>> P. S. P2327 de-deprecating volatile received a "consensus" straw poll.
>>>
>>>
>>> Discussion on Low Latency/Finance topics
>>>
>>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p1839r4.pdf
>>>
>>> Patrice's paper on games.
>>>
>>> P2300
>>> Swift
>>>
>>>
>>>
>>> Discussion about Games topics:
>>>
>>> P2388R1 - Minimum Contract Support: either Ignore or Check_and_abort
>>> <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2388r1.html>
>>>
>>> Patrice's WIP on Games issues.
>>>
>>> Finance topics from July 14, 2021.
>>>
>>> https://lists.isocpp.org/sg14/2021/06/0636.php
>>>
>>> https://lists.isocpp.org/sg14/2021/07/0642.php
>>>
>>> 2.2.1 any other proposal for reviews?
>>>
>>> Deterministic Exception for Embedded by James Renwick
>>>
>>> https://www.pure.ed.ac.uk/ws/portalfiles/portal/78829292/low_cost_deterministic_C_exceptions_for_embedded_systems.pdf
>>>
>>> Freestanding?
>>>
>>> SG14/SG19 features/issues/defects:
>>>
>>>
>>> https://docs.google.com/spreadsheets/d/1JnUJBO72QVURttkKr7gn0_WjP--P0vAne8JBfzbRiy0/edit#gid=0
>>>
>>> 2.3 Domain-specific discussions
>>>
>>> 2.3.1 SIG chairs
>>>
>>> - Embedded Programming chairs: Ben Craig, Wouter van Ooijen and Odin
>>> Holmes, John McFarlane
>>>
>>> - Financial/Trading chairs: Staffan TjernstrÃm
>>> Carl Cooke, Neal Horlock,
>>> - Games chairs: Rene Riviera, Guy Davidson and Paul Hampson, Patrice
>>> Roy
>>>
>>> - Linear Algebra chairs: Bob Steagall, Mark Hoemmen, Guy Davidson
>>>
>>> 2.4 Other Papers and proposals
>>>
>>> 2.5 Future F2F meetings:
>>>
>>> 2.6 future C++ Standard meetings:
>>> https://isocpp.org/std/meetings-and-participation/upcoming-meetings
>>>
>>> -
>>>
>>> 3. Any other business
>>> Reflector
>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>>> As well as look through papers marked "SG14" in recent standards
>>> committee
>>> paper mailings:
>>> http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/
>>> http://open-std.org/jtc1/sc22/wg21/docs/papers/2016/
>>>
>>> Code and proposal Staging area
>>> https://github.com/WG21-SG14/SG14
>>> 4. Review
>>>
>>> 4.1 Review and approve resolutions and issues [e.g., changes to SG's
>>> working draft]
>>>
>>> 4.2 Review action items (5 min)
>>>
>>> 5. Closing process
>>>
>>> 5.1 Establish next agenda
>>>
>>> 5.2 Future meeting
>>>
>>>
>>> *Mar 8, 2023 02:00 PM ET: Embedded
>>> *Apr 12, 2023 02:00 PM ET: Cancelled
>>> * May 10, 2023 02:00 PM ET: Cancelled
>>> * June 14, 2023 02:00 PM ET: Cancelled
>>> * July 12, 2023 02:00 PM ET: Finance
>>> * Aug 9, 2023 02:00 PM ET: Games
>>> * Sep 12, 2023 02:00 PM ET: Embedded
>>> * Oct 1: CPPCON
>>> * Oct 10, 2023 02:00 PM ET: Finance
>>> *Nov 8, 2023 02:00 PM ET: Kona F2F Cancelled
>>> * Dec 12, 2023 02:00 PM ET: Games
>>> _______________________________________________
>>> SG14 mailing list
>>> SG14_at_[hidden]
>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>>>
>> _______________________________________________
>> SG14 mailing list
>> SG14_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>>
>
Received on 2023-07-12 21:03:01