[Rd] ok to segfault with POSIXlt zone=NULL zone=""?

[Duncan Murdoch]

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 06/12/2016 12:27 PM, frederik at ofb.net wrote:
> Hi all,
>
> Here's a more minimal version of my earlier bug report (thanks, Joshua
> Ulrich):
>
> d=as.POSIXlt(Sys.time()); d$zone=NULL; d$zone=""; d
>
> I got some helpful, if glib, feedback from Joshua that the segfault
> may be caused by the changing of the order of the list elements in 'd'
> (representing the "internal structure" of the POSIXlt object).
>
> He seems to think that it's OK for R to segfault - I was wondering if
> someone else could lend a second opinion. My understanding is that we
> should try to avoid segfaulting as a way of handling errors, if only
> because they become much more difficult to debug when the R session is
> forced to quit.
>
> I don't know exactly which line is causing the bug, but looking at the
> code for do_formatPOSIXlt in "src/main/datetime.c", it seems that
> there would not be a huge performance penalty to add an extra sanity
> check to prevent this from occurring.
>
> Thank you,
>
> Frederick
>
> On Tue, Dec 06, 2016 at 04:37:20AM -0800, frederik at 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
>>
>>     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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>
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