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Subject: Re: Apr 8th Sg14 monthly call agenda
From: Patrice Roy (patricer_at_[hidden])
Date: 2020-04-09 08:55:28


Thanks Michael!

Le jeu. 9 avr. 2020 à 09:54, Michael Wong via SG14 <sg14_at_[hidden]>
a écrit :

> HI all, thanks I will update the minutes just before mailing it in.
>
> Here is a Google spreadsheet that is open to sign up to the github for
> joinigng the Low cost deterministic C++ exception for Embedded
> implementation:
>
>
> https://docs.google.com/spreadsheets/d/106_uuEy1mxVaBACgJ-cSegcTFTZfTZnjwvKNfmHBH5Y/edit#gid=0
>
> I have added the names entered here, and the names that registered during
> the Prague SG14 meeting, though I don't have your github names of the
> following folks. So please enter it in the spreadsheet. Thanks.
> Inbal Levi
>
> Sebastien Buttner
> Kristof Beyls
> Odin Holmes
> James Berrow
> Oliver Kowalke
> James Renwick
>
>
> On Thu, Apr 9, 2020 at 9:39 AM Ben Craig via SG14 <sg14_at_[hidden]>
> wrote:
>
>> Github user ben-craig. Sign me up
>>
>>
>>
>> *From:* SG14 <sg14-bounces_at_[hidden]> *On Behalf Of *Paul M.
>> Bendixen via SG14
>> *Sent:* Thursday, April 9, 2020 4:55 AM
>> *To:* sg14_at_[hidden]
>> *Cc:* Paul M. Bendixen <paulbendixen_at_[hidden]>
>> *Subject:* [EXTERNAL] Re: [SG14] Apr 8th Sg14 monthly call agenda
>>
>>
>>
>> Minor nit:
>>
>> My name is BendiXen, but maybe you used all the xs for variables ;-)
>>
>>
>>
>> My comment regarding cassert was to say that having different rules for
>> embedded and the rest of C++ was a hindrance to adoption ( e.g. using
>> libraries)
>>
>>
>>
>> Best
>>
>> Paul Bendixen
>>
>>
>>
>> tor. 9. apr. 2020 11.04 skrev Guy Cpp via SG14 <sg14_at_[hidden]>:
>>
>> Please add me to the attendee list; I turned up a little late.
>>
>>
>> Cheers,
>> G
>>
>>
>>
>> On Wed, 8 Apr 2020 at 21:00, Michael Wong via SG14 <sg14_at_[hidden]>
>> wrote:
>>
>>
>>
>>
>>
>> On Wed, Apr 8, 2020 at 11:55 AM Michael Wong <fraggamuffin_at_[hidden]>
>> wrote:
>>
>> Topic: SG14 Low Latency Monthly. Hi all, I have turned on high security
>> for this call in light of recent events.
>>
>> Hi,
>>
>> Michael Wong is inviting you to a scheduled Zoom meeting.
>>
>> Topic: SG14 monthly Apr 2020-Oct 2020
>> Time: Apr 8, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: May 13, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: June 10, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Jul 8, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Aug 12, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Sep 9, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Oct 14, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Join from PC, Mac, Linux, iOS or Android:
>> https://iso.zoom.us/j/819108882?pwd=L0pPZm5QRWlTYXdJditvU1JLdjFYUT09
>> <https://urldefense.com/v3/__https:/iso.zoom.us/j/819108882?pwd=L0pPZm5QRWlTYXdJditvU1JLdjFYUT09__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19WncSWZS$>
>> Password: 013549
>>
>> Or iPhone one-tap :
>> US: +13462487799,,819108882# or +14086380968,,819108882#
>> Or Telephone:
>> Dial(for higher quality, dial a number based on your current
>> location):
>> US: +1 346 248 7799 or +1 408 638 0968 or +1 646 876 9923 or
>> +1 669 900 6833 or +1 253 215 8782 or +1 301 715 8592 or +1 312 626 6799
>> or 877 853 5247 (Toll Free)
>> Meeting ID: 819 108 882
>> Password: 013549
>> International numbers available: https://iso.zoom.us/u/abhaIjFKLZ
>> <https://urldefense.com/v3/__https:/iso.zoom.us/u/abhaIjFKLZ__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19a085pg4$>
>>
>> Or Skype for Business (Lync):
>> https://iso.zoom.us/skype/819108882
>> <https://urldefense.com/v3/__https:/iso.zoom.us/skype/819108882__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19c_Sf0lz$>
>>
>>
>>
>> Agenda:
>>
>> 1. Opening and introductions
>>
>> 1.1 Roll call of participants
>>
>> Derek Haines
>>
>> Henry Miller
>>
>> James renwick
>>
>> Andrews Weis
>>
>> Antony Peacock
>>
>> ben Craig, Ben Saks
>>
>> BillyBaker
>>
>> Connor Horman
>>
>> Max Gardner
>>
>> Patrice Roy
>>
>> Paul Bendien
>>
>> Sophia Poirier
>>
>> Staffan Tjernstrom
>>
>> Steven Varga
>>
>> Jens Maurer
>>
>> Inbal Levi
>>
>> Michael Wong
>>
>> Dan Raviv?
>>
>> Charles Bay
>>
>> Matthew Butler
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> 1.2 Adopt agenda
>>
>> Approve.
>>
>> 1.3 Approve minutes from previous meeting, and approve publishing
>> previously approved minutes to ISOCPP.org
>>
>> Approve.
>>
>>
>>
>> 1.4 Action items from previous meetings
>>
>> 2. Main issues (125 min)
>>
>> 2.1 General logistics
>>
>> Prague summary
>>
>> Mailing deadline is monthly on 15th
>>
>> All meetings going online.
>>
>> 2.2 Paper reviews
>>
>>
>>
>> Low-cost Deterministic C++ Exceptions for Embedded Systems
>> <https://urldefense.com/v3/__https:/www.research.ed.ac.uk/portal/files/78829292/low_cost_deterministic_C_exceptions_for_embedded_systems.pdf__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19ZpJwLHg$>
>>
>> Low-cost Deterministic C++ Exceptions for Embedded Systems
>>
>> James Renwick
>>
>> James Renwick et al.
>>
>> BC: passing an address, so you can indirect jmp instead of return?
>>
>> leave optimzation off for now, what it this just look like normal code
>>
>>
>>
>> when propagating exception up the call stack, just do a return
>>
>> BC: regular processor, branch cost is small, but on gpu divergign control
>> throws is high, throwing an exception on gpu is already expensive
>>
>> for gpu instead of terminate might do a HW specific thing
>>
>> CH: too many banches will cross bank boundaries;
>>
>> Even with a nave implementaion, we can see n times better
>>
>>
>>
>> ST: precompield external libraries 1K allocated for stack and with only
>> 256 bytes from the stack, what happens? Right we dont deal with dynamic
>> library yet, but it doesnt make teh exception object unique, and nothing is
>> unique on the exception object here
>>
>> DLL and static libraries crossing boundary may be UB here or an ODR
>> violation
>>
>>
>>
>> JM: table reduction does not match waht you said about text increase
>> maching?
>>
>> because unwind library is gone
>>
>>
>>
>> BC: version of clang?
>>
>> clang 6
>>
>>
>>
>> CH:on function size vs binary size;
>>
>> should the catch block, which can be called out to another function,
>>
>>
>>
>> buffer on where to put EH object and it falls back to the heap, so this
>> can do the same thing
>>
>> need to inject parameter, which could thow., need to distinguisj C and
>> C++ function so need throw specifier added, abi change
>>
>> or pass by TLS
>>
>>
>>
>> a C language linkage, dont inject, standards says thata fn pointer inside
>> a structure,
>>
>> type of ptr
>>
>> extern C allowed to throw, so we can detect what linkage a fn has
>>
>> C adapting deterministic exception
>>
>> we just need implmentation with a compielr flag
>>
>> parameter injection will be an abi break
>>
>>
>>
>> exception_ptr was intended to allow copying to support bot hreference
>> counting heap allocated as is eager copy implementations
>>
>>
>>
>> you know the size because you call the copy constructor and not just
>> memcpy it
>>
>> resolve copy construction when you write the throw expression so you know
>> the size of the xception object
>>
>> but if pass exception ptr through to another functions object, that could
>> take a dynamic size,
>>
>> if you can pass exception ptr around, can assign it to global variable,
>> stack space does not matter, you have a life time problem; so it has to be
>> on the heap to solve this
>>
>> so if eh object lives on stack, cant touch the heap, the nwe have a
>> problem; yes you can outlive, so copy an exception ptr object stackframe,
>> then for these reasons
>>
>> exception_ptr is aimed at heap implementation
>>
>> so we propose similar that is agnostic, encapsulate exception object,
>> call get_current exception, then you are responsible for this object, no
>> reference count, so you move it around
>>
>>
>>
>> cross noexcept bounday with an exception ptr, want to pass exeption
>> through noexcept boundary without passing exception object as parameter for
>> the rethrowing case
>>
>>
>>
>> want std exception ptr that has shared ownership and unique ownership of
>> the exception object
>>
>>
>>
>> no language or library changes in this paper
>>
>> its an implementation report
>>
>> should we advise exception ptr is toxic
>>
>>
>>
>> Paul: claims is standard conformant, leaves out what noexcept specifier
>> mean
>>
>>
>>
>> Ben: it would no changes, there are proposal would be changing stuff
>> substantially, address cost benefit analysis of those papers
>>
>>
>>
>> some of the mitigation: adding noexcept blocks to mark large parts as
>> noexcept, change the calling convention to make it so a prebuilt C library
>> can work with this
>>
>>
>>
>> PB: C assert is verymuch a hint of adoption
>>
>>
>>
>> Exception_ptr: can we ban it in free_standing, or use Rust send
>>
>>
>>
>> exception_ptr on the heap is fine, problem is when you move it, it is
>> nolonger available in the catch block, if you copy exception its fine as
>> implementation only allow move only objects
>>
>>
>>
>> if it is moved onto the heap, then its a problem, but OK if you copy from
>> stack to heap
>>
>>
>>
>> open the github (limited form)and form a group and tthen come back to
>> discuss bridfing mechanism
>>
>>
>>
>> please reply to this thread if inetersted in joining this Exception
>> Handing for Embedded implementation group.
>>
>>
>>
>> P2057r0
>> <https://urldefense.com/v3/__http:/www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2057r0.pdf__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19V9euEDT$>
>>
>> SG14 SG19 Past, Present and Future status
>>
>> Michael Wong
>>
>> Michael Wong et al.
>>
>>
>>
>> PB: numeric proposal an ommission?Yes please add
>>
>> 2.2.1 any other proposal for reviews?
>>
>> MW: Interested in Networking RPC proposal? Yes
>>
>> ST: Error handling compendium?
>>
>> 2.3 Domain-specific discussions
>>
>> 2.3.1 SIG chairs
>>
>> - Embedded Programming chairs: Ben Craig, Wouter van Ooijen and Odin
>> Holmes, John McFarlane
>> <
>>
>> http://wiki.edg.com/bin/edit/Wg21belfast/McFarlane?topicparent=Wg21belfast.SG14CPPCON2019-09-17;nowysiwyg=1
>> <https://urldefense.com/v3/__http:/wiki.edg.com/bin/edit/Wg21belfast/McFarlane?topicparent=Wg21belfast.SG14CPPCON2019-09-17;nowysiwyg=1__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19TigatDr$>>
>>
>>
>> - Financial/Trading chairs: Stephan TJ, Carl Cooke, Neal Horlock,
>> Mateusz Pusz, Clay Trychta,
>> - Games chairs: Rene Riviera, Guy Davidson and Paul Hampson
>> - 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
>> <https://urldefense.com/v3/__https:/isocpp.org/std/meetings-and-participation/upcoming-meetings__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19aFyQm9I$>
>>
>> - 2020-11: (New York, tentative)
>> - 2021-02-22 to 27: Kona, HI, USA
>>
>> 3. Any other business
>> Reflector
>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
>> <https://urldefense.com/v3/__https:/lists.isocpp.org/mailman/listinfo.cgi/sg14__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19QgY4KHs$>
>> As well as look through papers marked "SG14" in recent standards
>> committee
>> paper mailings:
>> http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/
>> <https://urldefense.com/v3/__http:/open-std.org/jtc1/sc22/wg21/docs/papers/2015/__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19bnJhoER$>
>> http://open-std.org/jtc1/sc22/wg21/docs/papers/2016/
>> <https://urldefense.com/v3/__http:/open-std.org/jtc1/sc22/wg21/docs/papers/2016/__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19XBTPb27$>
>>
>> Code and proposal Staging area
>> https://github.com/WG21-SG14/SG14
>> <https://urldefense.com/v3/__https:/github.com/WG21-SG14/SG14__;!!FbZ0ZwI3Qg!5IDP-p-EEaQOMZrPdy1JsDOZnYyfcsWdkQDHhPfaWbyPCUKSIM-19UFYZFSE$>
>> 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
>>
>> Time: May 13, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: June 10, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Jul 8, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Aug 12, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Sep 9, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> Time: Oct 14, 2020 02:00 PM Eastern Time (US and Canada)
>>
>> _______________________________________________
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>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
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>>
>> _______________________________________________
>> SG14 mailing list
>> SG14_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/sg14
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>>
>> _______________________________________________
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