Sweave resource leak: leftover temp files (PR#7998)

On Tue, 12 Jul 2005, Duncan Murdoch wrote:

Prof Brian Ripley wrote:
This is actually a Windows bug.  Those files are unlink()ed, and it seems 
Windows is not respecting that (not an unknown phenomenon).  I have tried a 
few workarounds, and am about to commit one that seems to work.
I guess you mean the C unlink, since I don't see the R unlink being called.
Yes, I do, but the R unlink calls the C unlink and so has the same 
problem.

Generally deletes fail on Windows when files are locked, e.g. open for 
reading or writing.  I haven't seen Windows file deletes fail in other 
circumstances, so I suspect this was an R, MinGW or MSVCRT bug rather than a 
Windows bug.
But unlink() is required by POSIX to work when files are open, so it is a 
MSVCRT `feature' (and that is part of Windows since Win95 OSR2).  Indeed, 
there is nothing in the MSDN documentation on unlink() that says anything 
about not working if files are `locked'.

If people use the same name and arg sequence of a standard library call 
and partially implement it without saying so or mentioning the 
restrictions I believe it is perfectly reasonable to call that a bug.
This is documented in the API call DeleteFile.  I wouldn't call MSVCRT 
part of Windows, but I guess this is the same thing as saying that Linux 
is the kernel, not the whole collection of things you get in a Linux 
distribution.

Windows provides a different mechanism for this, the 
FILE_FLAG_DELETE_ON_CLOSE flag to CreateFile().  Your patch has solved 
the problem, so I can't see that it would be worthwhile using this, but 
one way to implement the POSIX behaviour would be to open a file with 
this flag, then immediately close it.  As long as all other handles to 
the file are eventually closed the file should be deleted.

Duncan

Duncan Murdoch
No files are left over on a decent operating system, e.g. Solaris or FC3 
Linux.

On Fri, 8 Jul 2005 murdoch at stats.uwo.ca wrote:

Harold, I've taken a closer look at your example and I'd call this an
Sweave bug.  It creates tempfiles each time you run it, and doesn't
delete them at the end.  For example:

list.files(tempdir())
character(0)

testfile <- system.file("Sweave", "Sweave-test-1.Rnw", package = "utils")
Sweave(testfile, out="junk.tex")
Writing to file junk.tex
Processing code chunks ...
1 : print term verbatim
2 : term hide
3 : echo print term verbatim
4 : term verbatim
5 : echo term verbatim
6 : echo term verbatim eps pdf
7 : echo term verbatim eps pdf

You can now run LaTeX on 'junk.tex'

list.files(tempdir())
[1] "Rf10523" "Rf13872" "Rf17129" "Rf2055"  "Rf2203"  "Rf2403"  "Rf27095"
[8] "Rf2892"  "Rf31415" "Rf5290"  "Rf6251"  "Rf6482"  "Rf7055"  "Rf724"

Sweave(testfile, out="C:/temp/junk.tex")
Writing to file C:/temp/junk.tex
Processing code chunks ...
1 : print term verbatim
2 : term hide
3 : echo print term verbatim
4 : term verbatim
5 : echo term verbatim
6 : echo term verbatim eps pdf
7 : echo term verbatim eps pdf

You can now run LaTeX on 'C:/temp/junk.tex'

list.files(tempdir())
[1] "Rf10523" "Rf12679" "Rf1311"  "Rf13484" "Rf13872" "Rf17129" "Rf17288"
[8] "Rf2055"  "Rf21774" "Rf2203"  "Rf23417" "Rf2403"  "Rf27095" "Rf2892"
[15] "Rf29444" "Rf31128" "Rf31415" "Rf32520" "Rf3338"  "Rf5290"  "Rf5551"
[22] "Rf6251"  "Rf6482"  "Rf7055"  "Rf724"   "Rf7543"  "Rf758"   "Rf7673"

unlink(list.files(tempdir(),full=T))
list.files(tempdir())
character(0)

Harold:  a workaround for this would be to wrap your Sweave call in
something like this:

keep <- list.files(tempdir(), full=TRUE)  # keep previous temp files

... Call Sweave here ...

temps <- list.files(tempdir(), full=TRUE)
unlink(temps[!(temps %in% keep)])  # delete the newly created ones

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