On 1/25/2008 8:25 AM, [EMAIL PROTECTED] wrote: > On Fri, 25 Jan 2008, [EMAIL PROTECTED] wrote: > >> In R 2.6.1, a couple of places (discovered using valgrind) where the >> requested size of string buffers fails to account correctly for the >> trailing null byte: >> >> 1. In src/appl/strsignif.c, 'f0' and 'form' at l. 108-9 each need at >> least 1 extra byte. >> >> 2. In src/main/util.c, 'out' at l. 1081 needs at least one extra byte. >> >> (Remember that the return value of strlen does not include the null byte.) > > But it is subtler than that. R_alloc contains the statement > > s = allocVector(RAWSXP, size + 1); > > and so does over-allocate by at least one (there is a rounding up to a > multiple of 8). This is a historical anomaly (it used to allocate a > CHARSXP that allowed for the null byte), but one which trying to eliminate > caused too many crashes in package code. > > I'd like to see the empirical evidence you have, as I have been unable to > trigger an overrun here.
That is not documented in Writing R Extensions or R Internals, so I think a change is needed, either to the docs or the calls. I've already changed these calls. I'd rather keep the docs as they are, because they give a sensible definition to the function. If the implementation protects against sloppy usage that's okay, but I don't think we should take advantage of it, in case some future maintainer notices the inconsistency and removes it. Duncan Murdoch ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
