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NextMethod causes R 2.2.0 to crash (PR#8416)

2 messages · Bill Venables, Henrik Bengtsson

Bill Venables
# 
I found writing the following default method the for the generic
function "julian" causes R to crash.


julian.default <- function(x, ...) {
        x <- as.Date(x)
        NextMethod("julian", x, ...)
}

Here is a test example
[1] "1972-09-27" "1972-09-28" "1972-09-29" "1972-09-30" "1972-10-01"
"1972-10-02" "1972-10-03"
 [8] "1972-10-04" "1972-10-05" "1972-10-06" "1972-10-07"
[1] "Date"
[1] 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010
attr(,"origin")
[1] "1970-01-01"
[1] "character"
< R crashes>

--please do not edit the information below--

Version:
 platform = i386-pc-mingw32
 arch = i386
 os = mingw32
 system = i386, mingw32
 status = 
 major = 2
 minor = 2.0
 year = 2005
 month = 10
 day = 06
 svn rev = 35749
 language = R



Bill Venables, 
CMIS, CSIRO Laboratories, 
PO Box 120, Cleveland, Qld. 4163 
AUSTRALIA 
Office Phone (email preferred): +61 7 3826 7251 
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mailto:Bill.Venables at csiro.au 
http://www.cmis.csiro.au/bill.venables/
Henrik Bengtsson
#
Bill.Venables at csiro.au wrote:
On Windows XP R 2.2.0 Patched (2005-11-21 r36410) you get:

Error: evaluation nested too deeply: infinite recursion / 
options(expressions=)?

and on Windows XP R 2.1.1 Patched (2005-09-19) you get:

Error: protect(): protection stack overflow

It seems that the R.2.2.0 revision you have does not protect against 
this.  I agree that it should not be possible to crash R, but is it 
valid to call NextMethod() in a default function? [R core, should this 
ever be allowed?]

I do not know exactly how NextMethod() is expected to work here, but I 
could imaging that 'x' has class 'Date' when NextMethod() is called and 
the "next" class will the be the default one so you call 
julian.default() again ending up in an infinite call.  This makes sense 
from the errors I get above.  Try this and see what you get in your version:

julian.default <- function(x, ...) {
   cat("In julian.default()\n")
   x <- as.Date(x)
   NextMethod("julian", x, ...)
}

Was you intention to do the following instead

  julian.default <- function(x, ...) {
    x <- as.Date(x)
    julian(x, ...)
  }

where julian() is the generic function?

Cheers

Henrik