+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 >
