[Python-Dev] Patch 595601

[Shane Hathaway]

Skip Montanaro wrote:
>     Tim>     http://www.python.org/sf/595601
> 
>     Tim> has been in limbo a long time.  Looks like it popped up in real
>     Tim> life, in Zope last week.
> 
>     Tim> Quickie: if you let run this long enough, it will die with a
>     Tim> segfault (and under any version of Python):
> 
>     ...
> 
> Isn't this a case of "so don't do that"?  I've never encountered this
> before, but then I don't close files in one thread while another holds a
> reference.
> 
> Would it be reasonable to raise an error or warning if a file's close()
> method was called when the reference count was greater than 1?

I think it would be very reasonable to raise an error if a file's 
close() method is called while another thread is executing a system call 
involving that file.  The Python refcount doesn't provide that 
information, so Jeremy, Tim, Barry, and I have been discussing the idea 
of maintaining a special refcount on PyFileObjects.  The new counter 
would be incremented before system calls involving f->f_fp and 
decremented afterward.  The counter would provide to the close() method 
enough information to know it should raise an error instead of closing 
the file.

What we're not sure of is whether we should be concerned about leaking 
file descriptors due to close() failing.  We'd also like some 
confirmation that fixing this bug is worth a small burden of complexity.

Shane

P.S. I think this is my First Post on Python-dev.  Howdy, all!