follow up to my previous post... the first four byte is out of my imagination, but the next 4 bytes indicates 16 that should be the following message size.
On Tuesday, May 19, 2015 at 11:54:01 PM UTC+2, Jim Muchow wrote: > I sent a question yesterday, but I don't see it as having been posted, > much less > responded to. My apologies for the redundancy if my original message is in > some > queue somewhere. > > ********** > > I'm trying to determine the utility of Valgrind in an app. The app uses > protocol buffers. > > I am seeing a message from Valgrind > > Syscall param write(buf) points to uninitialised byte(s) > > with the following info > > Address 0x11c7fa02 is 2 bytes inside a block of size 8,192 alloc'd > > At first, I thought it might be one of the fields in a message declared > optional, but > when I filled out the field, I got the same warning. In the process of > looking into this > more closely I was able to dump the buffer: > > 0x00 0x01 0xc1 0x09 0x00 0x00 0x00 0x10 <---- secret, > pre-header? > 0x08 0x00 0x10 0xa5 0xcb 0x96 0xad 0x0a > 0x1a 0x06 0x61 0x70 0x61 0x63 0x68 0x65 > > The latter 16 bytes are the message proper with three fields and I > understand how > they are created and interpreted from the Encoding spec (very helpful). It > is the first > eight bytes I don't understand. > > These first bytes are almost like a secret pre-header. It looks to me as > if the last four > bytes are a 32-bit length field. The number matches in this case and in > the other case in > which the optional field was left unset. I can't figure what the first > four bytes indicate. In > particular, the bytes 0xc1 and 0x09, which would start the area of the > supposedly > uninitialized bytes. > > Is there somewhere in the code I can look to see how this pre-header is > created. Or I > would be happy to research this myself if some documentation exists, but I > don't know > where to start looking. > > Thanks for any help, > jdm > > -- You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To unsubscribe from this group and stop receiving emails from it, send an email to protobuf+unsubscr...@googlegroups.com. To post to this group, send email to protobuf@googlegroups.com. Visit this group at http://groups.google.com/group/protobuf. For more options, visit https://groups.google.com/d/optout.
