On 7/17/2009 1:15 PM, Olaf Mersmann wrote:
Hi,
Excerpts from Torsten.Hothorn's message of Thu Jul 16 17:20:10 +0200 2009:
`model.matrix' might kill R with a segfault (on a illposed problem, but anyway):
mydf <- as.data.frame(sapply(1:40, function(i) gl(2, 100)))
f <- as.formula(paste("~ - 1 + ", paste(names(mydf), collapse = ":"), sep = ""))
X <- model.matrix(f, data = mydf)
*** caught segfault ***
address 0x18, cause 'memory not mapped'
Segmentation fault
I've taken a look at this. The problem lies in lines 1784 - 1798 of
src/main/model.c. What happens is that 'k' overflows (signed
int). That means k is 0 after the loop an nc is set to 0. That means
the allocated model matrix 'x' is too small which results in the
observed segfault.
I can provide a patch which checks for overflow and throws an error if
that is the desired behaviour.
Thanks for tracking this down. I'll fix it; your patch would likely be
helpful, but your description is clear enough.
Duncan Murdoch
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