Thanks for the reply, Duncan.
It looks like Martin can commit a patch faster than I can open a bug
report...
Frederick
On Tue, Dec 06, 2016 at 12:39:32PM -0500, Duncan Murdoch wrote:
> I agree this is a bug; R should never segfault. I wouldn't call it a high
> priority one, since you can avoid the problem by not messing with R's
> internal structures.
>
> It's unlikely to get fixed unless someone posts it as a bug report to
> bugs.r-project.org (because low priority bugs reported only on mailing lists
> get forgotten).
>
> So please post a minimal example there, possibly accompanied with a patch.
> If you don't have an account, you can write to me privately and I'll set one
> up for you. (We no longer allow people to create their own accounts because
> of abuse by spammers.)
>
> Duncan Murdoch
On Tue, Dec 06, 2016 at 06:49:05PM +0100, Martin Maechler wrote:
> >>>>> Joshua Ulrich <josh.m.ulr...@gmail.com>
> >>>>> on Tue, 6 Dec 2016 09:51:16 -0600 writes:
>
> > On Tue, Dec 6, 2016 at 6:37 AM, <frede...@ofb.net> wrote:
> >> Hi all,
> >>
> >> I ran into a segfault while playing with dates.
> >>
> >> $ R --no-init-file
> >> ...
> >> > library(lubridate); d=as.POSIXlt(floor_date(Sys.time(),"year"));
> d$zone=NULL; d$zone=""; d
> >>
> > If you're asking about a bug in R, you should provide a *minimal*
> > reproducible example (i.e. one without any package dependencies).
> > This has nothing to do with lubridate, so you can reproduce the
> > behavior with:
>
> > d <- as.POSIXlt(Sys.time())
> > d$zone <- NULL
> > d$zone <- ""
> > d
>
> [..........]
>
> >> Hope I'm not doing something illegal...
> >>
> > You are. You're changing the internal structure of a POSIXlt object
> > by re-ordering the list elements. You should not expect a malformed
> > POSIXlt object to behave as if it's correctly formed. You can see
> > it's malformed by comparing it's unclass()'d output.
>
> > d <- as.POSIXlt(Sys.time())
> > unclass(d) # valid POSIXlt object
> > d$zone <- NULL
> > d$zone <- ""
> > unclass(d) # your malformed POSIXlt object
>
> Indeed, really illegal, i.e. "against the law" ... ;-)
>
> Thank you, Joshua!
>
> Still, if R segfaults without the user explicitly
> calling .Call(), .Internal() or similar -- as here --
> we usually acknowledge there *is* a bug in R .. even if it is
> only triggered by a users "illegal" messing around.
>
> an MRE for the above, where I really only re-order the "internal" list:
>
> d <- as.POSIXlt("2016-12-06"); dz <- d$zone; d$zone <- NULL; d$zone <- dz; f
> <- format(d)
>
> > *** caught segfault ***
> > address 0x80000020, cause 'memory not mapped'
>
> > Traceback:
> > 1: format.POSIXlt(d)
> > 2: format(d)
>
> The current code is "optimized for speed" (not perfectly), and
> a patch should hopefully address the C code.
>
> Note that a smaller MRE -- which does *not* re-order, but just
> invalidate the time zone is
>
> d <- as.POSIXlt("2016-12-06"); d$zone <- 1; f <- format(d)
>
> ------
>
> I have now committed a "minimal" patch (to the C code) which for
> the above two cases gives a sensible error rather than a
> seg.fault :
>
> > d <- as.POSIXlt("2016-12-06"); d$zone <- 1 ; f <- format(d)
> Error in format.POSIXlt(d) :
> invalid 'zone' component in "POSIXlt" structure
>
> > d <- as.POSIXlt("2016-12-06"); dz <- d$zone; d$zone <- NULL; d$zone <-
> dz; f <- format(d)
> Error in format.POSIXlt(d) :
> invalid 'zone' component in "POSIXlt" structure
> >
>
> I guess that it should still be possible to produce a segfault
> with invalid 'POSIXlt' structures though.
>
> Martin
>
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