With respect to the implementation code for the paper shown at today's meeting, I would be very interested to take a look at it, and maybe poke around. If its needed, my github username is chorman0773._______________________________________________On Wed, Apr 8, 2020 at 16:00 Michael Wong via SG14 <sg14@lists.isocpp.org> wrote:On Wed, Apr 8, 2020 at 11:55 AM Michael Wong <fraggamuffin@gmail.com> 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)
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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://iso.zoom.us/skype/819108882Agenda:
1. Opening and introductions
1.1 Roll call of participants
Derek HainesHenry MillerJames renwickAndrews WeisAntony Peacockben Craig, Ben SaksBillyBakerConnor HormanMax GardnerPatrice RoyPaul BendienSophia PoirierStaffan TjernstromSteven VargaJens MaurerInbal LeviMichael WongDan Raviv?Charles BayMatthew Butler
1.2 Adopt agenda
Approve.
1.3 Approve minutes from previous meeting, and approve publishing
previously approved minutes to ISOCPP.orgApprove.
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 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 codewhen propagating exception up the call stack, just do a returnBC: regular processor, branch cost is small, but on gpu divergign control throws is high, throwing an exception on gpu is already expensivefor gpu instead of terminate might do a HW specific thingCH: too many banches will cross bank boundaries;Even with a nave implementaion, we can see n times betterST: 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 hereDLL and static libraries crossing boundary may be UB here or an ODR violationJM: table reduction does not match waht you said about text increase maching?because unwind library is goneBC: version of clang?clang 6CH: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 thingneed to inject parameter, which could thow., need to distinguisj C and C++ function so need throw specifier added, abi changeor pass by TLSa C language linkage, dont inject, standards says thata fn pointer inside a structure,type of ptrextern C allowed to throw, so we can detect what linkage a fn hasC adapting deterministic exceptionwe just need implmentation with a compielr flagparameter injection will be an abi breakexception_ptr was intended to allow copying to support bot hreference counting heap allocated as is eager copy implementationsyou know the size because you call the copy constructor and not just memcpy itresolve copy construction when you write the throw expression so you know the size of the xception objectbut 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 thisso 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 reasonsexception_ptr is aimed at heap implementationso 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 aroundcross noexcept bounday with an exception ptr, want to pass exeption through noexcept boundary without passing exception object as parameter for the rethrowing casewant std exception ptr that has shared ownership and unique ownership of the exception objectno language or library changes in this paperits an implementation reportshould we advise exception ptr is toxicPaul: claims is standard conformant, leaves out what noexcept specifier meanBen: it would no changes, there are proposal would be changing stuff substantially, address cost benefit analysis of those paperssome 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 thisPB: C assert is verymuch a hint of adoptionException_ptr: can we ban it in free_standing, or use Rust sendexception_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 objectsif it is moved onto the heap, then its a problem, but OK if you copy from stack to heapopen the github (limited form)and form a group and tthen come back to discuss bridfing mechanismplease reply to this thread if inetersted in joining this Exception Handing for Embedded implementation group.
P2057r0 SG14 SG19 Past, Present and Future status Michael Wong Michael Wong et al. PB: numeric proposal an ommission?Yes please add2.2.1 any other proposal for reviews?
MW: Interested in Networking RPC proposal? YesST: 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>
- 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
- 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
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
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)
SG14 mailing list
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