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.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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