Re: [Rd] segfault with POSIXlt zone=NULL zone=""

2016-12-06 Thread frederik 
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 
> > on Tue, 6 Dec 2016 09:51:16 -0600 writes:
> 
> > On Tue, Dec 6, 2016 at 6:37 AM,   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$zone <- dz; f 
> <- format(d)
> 
> >  *** caught segfault ***
> > address 0x8020, cause 'memory not mapped'
> 
> > Traceback:
> >  1: format.POSIXlt(d)
> >  2: format(d)
> 
> The current code is "optimized for speed" (not perfectly), and
> a patch should hopefully address the C code.
> 
> Note that a smaller MRE -- which does *not* re-order, but just
> invalidate the time zone is
> 
>   d <- as.POSIXlt("2016-12-06"); d$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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Re: [Rd] segfault with POSIXlt zone=NULL zone=""

2016-12-06 Thread Martin Maechler 
> Joshua Ulrich 
> on Tue, 6 Dec 2016 09:51:16 -0600 writes:

> On Tue, Dec 6, 2016 at 6:37 AM,   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 0x8020, 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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Re: [Rd] segfault with POSIXlt zone=NULL zone=""

2016-12-06 Thread Joshua Ulrich 
On Tue, Dec 6, 2016 at 10:30 AM,   wrote:
> Hi Joshua,
>
> Thank you for minimizing my test case.
>
>> > 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
>
> I don't know if these questions are not already obvious, but:
>
> 1. Is there a reasonable way to fail more elegantly when a user makes
> this mistake?
>
It's not just "this mistake".  See below.

> 2. Should we update the documentation for POSIXlt to warn people that
> the optional "zone" list element must precede the optional "gmtoff"
> list element, in cases where both are present?
>
No, because that's not the only way to create a malformed POSIXlt
object. Reordering *any* of the elements results in a segfault, and
there are probably other things you could do to the internal structure
of POSIXlt objects to cause segfaults.

Maybe update the documentation to say, "If you update the internal
structure of a POSIXlt object, you deserve whatever happens."? ;-)

> Thanks,
>
> Frederick



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Re: [Rd] segfault with POSIXlt zone=NULL zone=""

2016-12-06 Thread frederik 
Hi Joshua,

Thank you for minimizing my test case.

> > 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

I don't know if these questions are not already obvious, but:

1. Is there a reasonable way to fail more elegantly when a user makes
this mistake?

2. Should we update the documentation for POSIXlt to warn people that
the optional "zone" list element must precede the optional "gmtoff"
list element, in cases where both are present?

Thanks,

Frederick

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Re: [Rd] segfault with POSIXlt zone=NULL zone=""

2016-12-06 Thread Joshua Ulrich 
On Tue, Dec 6, 2016 at 6:37 AM,   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

> Attaching package: ‘lubridate’
>
> The following object is masked from ‘package:base’:
>
> date
>
> Warning message:
> package ‘lubridate’ was built under R version 3.4.0
>
>  *** caught segfault ***
> address (nil), cause 'unknown'
>
> Traceback:
>  1: format.POSIXlt(x, usetz = TRUE)
>  2: format(x, usetz = TRUE)
>  3: print(format(x, usetz = TRUE), ...)
>  4: print.POSIXlt(x)
>  5: function (x, ...) UseMethod("print")(x)
>
> Possible actions:
> ...
>
> 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

> Thanks,
>
> Frederick
>
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[Rd] segfault with POSIXlt zone=NULL zone=""

2016-12-06 Thread frederik 
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

Attaching package: ‘lubridate’

The following object is masked from ‘package:base’:

date

Warning message:
package ‘lubridate’ was built under R version 3.4.0 

 *** caught segfault ***
address (nil), cause 'unknown'

Traceback:
 1: format.POSIXlt(x, usetz = TRUE)
 2: format(x, usetz = TRUE)
 3: print(format(x, usetz = TRUE), ...)
 4: print.POSIXlt(x)
 5: function (x, ...) UseMethod("print")(x)

Possible actions:
...

Hope I'm not doing something illegal...

Thanks,

Frederick

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