> > > 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 >>> >>
