We need some more PMC members to look at this vote. I know the issue is esoteric but please let us know if you have questions.
On Thu, Aug 15, 2019 at 3:35 AM Micah Kornfield <emkornfi...@gmail.com> wrote: > > > > > > > Actually, it looks like my Mac's version of UBSAN doesn't detect the issue > > at all. I will try on linux a by EOD. > > Actually, the issue was I had alignment checks off. I verify this works > and it appears there is a UBSan issue with flatbuffers::Verify (I'll try to > see if I can find the issue and make a PR upstream). > > On Thu, Aug 15, 2019 at 1:03 AM Micah Kornfield <emkornfi...@gmail.com> > wrote: > > > I verified with these changes [1], without backwards compatibility > >> support, UBSAN runs cleanly for IPC tests in C++ > > > > Actually, it looks like my Mac's version of UBSAN doesn't detect the issue > > at all. I will try on linux a by EOD. > > > > On Thu, Aug 15, 2019 at 12:52 AM Micah Kornfield <emkornfi...@gmail.com> > > wrote: > > > >> +1 > >> > >> I verified with these changes [1], without backwards compatibility > >> support, UBSAN runs cleanly for IPC tests in C++ > >> > >> Just wanted to clarify: > >> > >>> Additionally with this vote, we want to formally approve the change to > >>> the Arrow "file" format to always write the (new 8-byte) end-of-stream > >>> marker, which enables code that processes Arrow streams to safely read > >>> the file's internal messages as though they were a normal stream. > >> > >> This only allows for reading messages safely, we still aren't > >> guaranteeing dictionary batches occur in the file before they are used, > >> correct? > >> > >> Thanks, > >> Micah > >> > >> [1] > >> https://github.com/emkornfield/arrow/commit/8b8348d8bcf62b50c35ddb4926f3d501b4f7147c > >> > >> > >> On Wed, Aug 14, 2019 at 3:43 PM Wes McKinney <wesmck...@gmail.com> wrote: > >> > >>> hi all, > >>> > >>> As we've been discussing [1], there is a need to introduce 4 bytes of > >>> padding into the preamble of the "encapsulated IPC message" format to > >>> ensure that the Flatbuffers metadata payload begins on an 8-byte > >>> aligned memory offset. The alternative to this would be for Arrow > >>> implementations where alignment is important (e.g. C or C++) to copy > >>> the metadata (which is not always small) into memory when it is > >>> unaligned. > >>> > >>> Micah has proposed to address this by adding a > >>> 4-byte "continuation" value at the beginning of the payload > >>> having the value 0xFFFFFFFF. The reason to do it this way is that > >>> old clients will see an invalid length (what is currently the > >>> first 4 bytes of the message -- a 32-bit little endian signed > >>> integer indicating the metadata length) rather than potentially > >>> crashing on a valid length. We also propose to expand the "end of > >>> stream" marker used in the stream and file format from 4 to 8 > >>> bytes. This has the additional effect of aligning the file footer > >>> defined in File.fbs. > >>> > >>> This would be a backwards incompatible protocol change, so older Arrow > >>> libraries would not be able to read these new messages. Maintaining > >>> forward compatibility (reading data produced by older libraries) would > >>> be possible as we can reason that a value other than the continuation > >>> value was produced by an older library (and then validate the > >>> Flatbuffer message of course). Arrow implementations could offer a > >>> backward compatibility mode for the sake of old readers if they desire > >>> (this may also assist with testing). > >>> > >>> Additionally with this vote, we want to formally approve the change to > >>> the Arrow "file" format to always write the (new 8-byte) end-of-stream > >>> marker, which enables code that processes Arrow streams to safely read > >>> the file's internal messages as though they were a normal stream. > >>> > >>> The PR making these changes to the IPC documentation is here > >>> > >>> https://github.com/apache/arrow/pull/4951 > >>> > >>> Please vote to accept these changes. This vote will be open for at > >>> least 72 hours > >>> > >>> [ ] +1 Adopt these Arrow protocol changes > >>> [ ] +0 > >>> [ ] -1 I disagree because... > >>> > >>> Here is my vote: +1 > >>> > >>> Thanks, > >>> Wes > >>> > >>> [1]: > >>> https://lists.apache.org/thread.html/8440be572c49b7b2ffb76b63e6d935ada9efd9c1c2021369b6d27786@%3Cdev.arrow.apache.org%3E > >>> > >>
