From murdoch.duncan at gmail.com  Tue Jul  4 16:52:39 2017
From: murdoch.duncan at gmail.com (Duncan Murdoch)
Date: Tue, 4 Jul 2017 10:52:39 -0400
Subject: [Rd] write.csv
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On 04/07/2017 10:01 AM, Jim Hester wrote:
> On linux at least you can use `/dev/full` [1] to test writing to a full device.
>
>     > echo 'foo' > /dev/full
>     bash: echo: write error: No space left on device

Unfortunately, I get a permission denied error if I try to write there 
from MacOS.  I don't know if Windows has an equivalent.

I've taken a look at the code.  Essentially it comes down to a call to 
the C function vfprintf, which is supposed to return the number of bytes 
written, or a negative value for an error. This return value is often 
not checked; in particular, write.table and friends don't check it.

I'll add code to signal an error if there's a negative value.

I don't think it's feasible to check the number of bytes (formatted text 
with possible translation to a different encoding could have any number 
of bytes) if it's positive.  So hopefully all of our file systems will 
correctly signal an error, and not just report how many bytes were 
successfully written.

>
> Although that won't be a perfect test for this case where part of the
> file is written successfully.
>
> An alternative suggestion for testing this is to create and mount a
> loop device [2] with a small file.
>
> [1]: https://en.wikipedia.org/wiki//dev/full
> [2]: https://stackoverflow.com/a/16044420/2055486

Loop devices sound ideal, but seem to be Linux-only (at least with that 
recipe).

Duncan


>
> On Tue, Jul 4, 2017 at 3:38 PM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>> On 04/07/2017 8:40 AM, Lipatz Jean-Luc wrote:
>>>
>>> I would really like the bug fixed. At least this one, because I know
>>> people in my institute using this function.
>>> I understand your arguments about open source, but I also saw in this mail
>>> list a proposal for a fix for this bug for which there were no answer from
>>> the people who are able to include it in the distribution. It looks like if
>>> there were interesting bugs and the other ones.
>>
>>
>> Please post a link to that, and I'll look.  Bug reports should be posted to
>> the bug list.  It's unfortunate that it is currently so difficult to do so,
>> but if they are only posted here, they are often overlooked.
>>
>>> I don't understand the other arguments : the example was reproduced with a
>>> simple USB key and you cannot state that a disk will eternally be empty
>>> enough, specially when it has several users.
>>
>>
>> I am not denying that it's a bug, I'm just saying that it is a difficult one
>> to test automatically (so we probably won't add a regression test once it's
>> fixed), and it's not one that has been reported often.  I didn't know there
>> were any reports before yours.
>>
>> Duncan Murdoch
>>
>>
>>> JLL
>>>
>>>
>>> -----Message d'origine-----
>>> De : Duncan Murdoch [mailto:murdoch.duncan at gmail.com]
>>> Envoy? : mardi 4 juillet 2017 14:24
>>> ? : Lipatz Jean-Luc; r-devel at r-project.org
>>> Objet : Re: [Rd] write.csv
>>>
>>> On 04/07/2017 5:40 AM, Lipatz Jean-Luc wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I am currently studying how to generalize the usage of R in my
>>>> statistical institute and I encountered a problem that I cannot declare on
>>>> bugzilla (cannot understand why).
>>>
>>>
>>> Bugzilla was badly abused by spammers last year, so you need to have your
>>> account created manually by one of the admins to post there.  Write to me
>>> privately if you'd like me to create an account for you.  (If you want it
>>> attached to a different email address, that's fine.)
>>>
>>> Sorry for trying this mailing list but I am really worried about the
>>> problem itself and the possible implications in using R in a professionnal
>>> data production context.
>>>>
>>>> The issue about 'write.csv' is that it just doesn't check if there is
>>>> enough space on disk and doesn't report failure to write data.
>>>>
>>>> Example (R 3.4.0 windows 32 bits, but I reproduced the problem with older
>>>> versions and under Mac OS/X)
>>>>
>>>>> fwrite(as.list(1:1000000),"G:/Test")
>>>>
>>>> Error in fwrite(as.list(1:1e+06), "G:/Test") :
>>>>   No space left on device: 'G:/Test'
>>>>>
>>>>> write.csv(1:1000000,"G:/Test")
>>>>>
>>>>
>>>> I have a big concern here, because it means that you could save some
>>>> important data at one point of time and discover a long time after that you
>>>> actually lost them.
>>>
>>>  > I suppose that the fix is relatively straightforward, but how can we
>>> be sure that there is no another function with the same bad properties?
>>>
>>> R is open source.  You could work out the patch for this bug, and in the
>>> process see the pattern of coding that leads to it.  Then you'll know if
>>> other functions use the same buggy pattern.
>>>
>>>> Is the lesson that you should not use a R function, even from the core,
>>>> without having personnally tested it against extreme conditions?
>>>
>>>
>>> I think the answer to that is yes.  Most people never write such big
>>> files that they fill their disk:  if they did, all sorts of things would
>>> go wrong on their systems.  So this kind of extreme condition isn't
>>> often tested.  It's not easy to test in a platform independent way:  R
>>> would need to be able to create a volume with a small capacity.  That's
>>> a very system-dependent thing to do.
>>>
>>>> And wouldn't it be the work of the developpers to do such elementary
>>>> tests?
>>>
>>>
>>> Again, R is open source.  You can and should contribute code (and
>>> therefore become one of the developers) if you are working in unusual
>>> conditions.
>>>
>>> R states quite clearly in the welcome message every time it starts: "R
>>> is free software and comes with ABSOLUTELY NO WARRANTY."  This is
>>> essentially the same lack of warranty that you get with commercial
>>> software, though it's stated a lot more clearly.
>>>
>>> Duncan Murdoch
>>>
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel



[Rd] write.csv
Duncan Murdoch