[Rd] segfault during build of 2.1.0 on RH9; print.POSIXct implicated (PR#7827)

[Jskud at jskud.com]

In attempting to build R using 

	rpmbuild --rebuild R-2.1.0-0.fdr.2.fc3.src.rpm 

on a fairly up-to-date RedHat 9 system (that is, with patches installed
through May 1 2004), it failed at the make check-all step.

The problem was reproducible by going into the tests directory and

	make test-Segfault

The last lines of the saved file no-segfault.Rout.fail are

> > ##  c.POSIXct  :
> > f <- get("c.POSIXct", pos = 'package:base')
> > f()
> character(0)
> > f(NULL)
> character(0)
> > f(,NULL)
> Error in lapply(list(...), unclass) : argument is missing, with no default
> > f(NULL,NULL)
> character(0)
> > f(list())
> character(0)
> > f(l0)
> character(0)

I was able to reproduce the problem (a segfault) as the following simple
transcript demonstrates: 

    LC_ALL=C SRCDIR=. R_DEFAULT_PACKAGES= ../bin/R --vanilla

    R : Copyright 2005, The R Foundation for Statistical Computing
    Version 2.1.0  (2005-04-18), ISBN 3-900051-07-0

    R is free software and comes with ABSOLUTELY NO WARRANTY.
    You are welcome to redistribute it under certain conditions.
    Type 'license()' or 'licence()' for distribution details.

    R is a collaborative project with many contributors.
    Type 'contributors()' for more information and
    'citation()' on how to cite R or R packages in publications.

    Type 'demo()' for some demos, 'help()' for on-line help, or
    'help.start()' for a HTML browser interface to help.
    Type 'q()' to quit R.

    > unusual_but_ok <- c.POSIXlt(character(0))
    > unusual_but_ok
    character(0)
    > unusual_and_faults <- c.POSIXct(character(0))
    > unusual_and_faults
    Segmentation fault

Running this test program under gdb, we find that we're running off the
end of the stack, with 4222 stack frames showing -- apparently in an
infinite recursion -- "as.character" shows up every 69 function calls:

#64 0x080ea1ef in Rf_usemethod (generic=0x81c8b12 "as.character", obj=0x0, call=0x85a04f4, 
    args=0x8af8b00, rho=0x8af8b70, callrho=0x8af8b70, defrho=0x829d4c0, ans=0xbff042b8)
    at objects.c:328

#133 0x080ea1ef in Rf_usemethod (generic=0x81c8b12 "as.character", obj=0x0, call=0x85a04f4, 
    args=0x8af35f0, rho=0x8af3660, callrho=0x8af3660, defrho=0x829d4c0, ans=0xbff08538)
    at objects.c:328

#202 0x080ea1ef in Rf_usemethod (generic=0x81c8b12 "as.character", obj=0x0, call=0x85a04f4, 
    args=0x8aeca08, rho=0x8aeca78, callrho=0x8aeca78, defrho=0x829d4c0, ans=0xbff0c7b8)
    at objects.c:328

#271 0x080ea1ef in Rf_usemethod (generic=0x81c8b12 "as.character", obj=0x0, call=0x85a04f4, 
    args=0x8ae7514, rho=0x8ae7584, callrho=0x8ae7584, defrho=0x829d4c0, ans=0xbff10a38)
    at objects.c:328

#340 0x080ea1ef in Rf_usemethod (generic=0x81c8b12 "as.character", obj=0x0, call=0x85a04f4, 
    args=0x8ade4c0, rho=0x8ade530, callrho=0x8ade530, defrho=0x829d4c0, ans=0xbff14cb8)
    at objects.c:328

So it would seem that *printing* the unusual POSIXct value is suspect.
Looking at a R-1.8.1 install, we find these definitions in base/R/base:

    print.POSIXct <- function(x, ...)
    {
	print(format(x, usetz=TRUE), ...)
	invisible(x)
    }

    print.POSIXlt <- function(x, ...)
    {
	print(format(x, usetz=TRUE), ...)
	invisible(x)
    }

However, looking at the 2.1.0 src file
R-2.1.0/src/library/base/R/datetime.R, we find

    print.POSIXct <- function(x, ...)
    {
	print(format(x, usetz=TRUE, ...), ...)
	invisible(x)
    }

    print.POSIXlt <- function(x, ...)
    {
	print(format(x, usetz=TRUE), ...)
	invisible(x)
    }

Note the suspicious definition of print.POSIXct using *two* sets of
ellipses, and that the print.POSIXct and print.POSIXlt definitions no
longer match.

/Jskud

--please do not edit the information below--

Version:
 platform = i686-pc-linux-gnu
 arch = i686
 os = linux-gnu
 system = i686, linux-gnu
 status = 
 major = 2
 minor = 1.0
 year = 2005
 month = 04
 day = 18
 language = R

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