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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/protobuf. For more options, visit https://groups.google.com/d/optout.
