On Aug 29, 2013, at 9:39 AM, Hadley Wickham wrote: > Hi all, > > Why is the object size of an empty vector 40 bytes? (At least in 64-bit R.) > > object.size(integer(0)) > # 40 bytes > > Reading R internals, it looks like it should be: > > * 4 bytes: sxpinfo header (= 32 bits) > * 8 bytes: pointer to attributes > * 8 bytes: pointer to next node > * 8 bytes: pointer to previous node > * 4 bytes: length > * 4 bytes: true length > > = 36 bytes > > Where are the extra 4 bytes coming from? What have I missed? >
Alignment of pointers -- there are 4 bytes of padding on 64-bit machines after sxpinfo > I thought it might be for memory alignment, but if it was padded by an > additional 4 bytes, then an integer vector of length 1 should be the > same size, assuming I've interpreted the comment about "aligned as > required" correctly. > > Thanks! > > Hadley > > -- > Chief Scientist, RStudio > http://had.co.nz/ > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
