Duncan Murdoch has written at Thu, 6 Jul 2017 13:58:10 -0400
On 06/07/2017 5:21 AM, Serguei Sokol wrote:
I propose the following patch against the current
R-devel/src/main/connection.c (cf. attached file).
It gives (on my linux box):
> fc=file("/dev/full", "w")
> write.csv("a", file=fc)
Error in writeLines(paste(col.names, collapse = sep), file, sep = eol) :
system call failure on writing
> close(fc)
Serguei.
I suspect that flushing on every write will slow things down too much.
That's quite plausible.
I think a better approach is to catch the error in the Rconn_printf
calls (as R-devel currently does), and also catch errors on
con->close(con). This one requires more changes to the source, so it
may be a day or two before I commit.
I have testes it on file_close() and it works (cf. attached patch):
> fc=file("/dev/full", "w")
> write.csv("a", file=fc)
> close(fc)
Error in close.connection(fc) : closing file failed
One thing I have to look into: is anyone making use of the fact that
the R-level close.connection() function can return -1 to signal an
error? Base R ignores that, which is why we need to do something, but
if packages are using it, things need to be changed carefully. I
can't just change it to raise an error instead.
As you can see in the patch, no need to change close.connection() function
but we have to add a test of con->status to all *_close() functions
(gzfile_close() and co.)
Serguei.
Le 05/07/2017 à 15:33, Serguei Sokol a écrit :
Le 05/07/2017 à 14:46, Serguei Sokol a écrit :
Le 05/07/2017 à 13:09, Duncan Murdoch a écrit :
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.
I correct myself. In my test, fprintf() returned -1 for another
reason (connection was already closed
at this moment)
However, if fvprintf(...) is followed by res=fflush(con) then res is -1
if we try to write on /dev/full. May be we have to use this to trigger
an error message in R.
Serguei.
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.dun...@gmail.com
<mailto:murdoch.dun...@gmail.com>> wrote:
On 04/07/2017 11:50 AM, Jean-Sébastien 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
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Index: connections.c
===================================================================
--- connections.c (revision 72894)
+++ connections.c (working copy)
@@ -769,6 +769,8 @@
#ifdef Win32
if(this->anon_file) unlink(this->name);
#endif
+ if(con->status < 0)
+ error(_("closing file failed"));
}
static int file_vfprintf(Rconnection con, const char *format, va_list ap)
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