[New Patch] Fix disk corruption when writing

Le 05/07/2017 ? 13:09, Duncan Murdoch a ?crit :

On 05/07/2017 5:26 AM, January W. wrote:

I tried the newest patch, but it does not seem to work for me (on
Linux). Despite the check in Rconn_printf, the write.csv happily writes
to /dev/full and does not report an error. When I added a printf("%d\n",
res); to the Rconn_printf() definition, I see only positive values
returned by the vfprintf call.

That's likely because you aren't writing enough to actually trigger a write to disk during the write.  Writes are buffered, and the error doesn't happen 
until the buffer is written.

I can confirm this behavior with fvprintf(). Small and medium sized writings
on /dev/full don't trigger error and 1MB does.

But if fprintf() is used, it returns a negative value from the very first byte written.

  The regression test I put in had this problem; I'm working on MacOS and Windows, so I never got to actually try it before committing.

Unfortunately, it doesn't look possible to catch the final flush of the buffer when the connection is closed, so small writes won't trigger any error.

It's also possible that whatever system you're on doesn't signal an error when the write fails.

Duncan Murdoch

Cheers,

j.


On 4 July 2017 at 21:37, Duncan Murdoch <murdoch.duncan at gmail.com
<mailto:murdoch.duncan at gmail.com>> wrote:

    On 04/07/2017 11:50 AM, Jean-S?bastien Bevilacqua wrote:

        Hello,
        You can find here a patch to fix disk corruption.
        When your disk is full, the write function exit without error
        but the file
        is truncated.

https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17243
<https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17243>


    Thanks.  I didn't see that when it came through (or did and forgot).
    I'll probably move the error check to a lower level (in the
    Rconn_printf function), if tests show that works.

    Duncan Murdoch