[darcs-users] DeleteFile on Windows (was: Re: hashed-storage work now merged in (woo!))

Zooko Wilcox-O'Hearn zooko at zooko.com
Thu Oct 8 23:13:27 UTC 2009

On Thursday,2009-10-08, at 16:47 , Jason Dagit wrote:

> This appears to assume:
> * On windows you can move a file even if it is open

Not generally, no.  The same rule that prevents you from deleting an  
open file also prevents you from moving it.

The idiom I use is "If you're letting a finalizer do something, that  
means you don't really care if it never gets done." (credit to JP  
Calderone for teaching me this).

So, instead I have an explicit "clean up this thing" procedure that I  
call when I know I'm done with the resource, and as an additional  
"belt and suspenders" I sometimes have a finalizer that invokes that  
explicit cleanup procedure.

This means that you have to figure out whether something else is also  
using the same resource, in case that something else isn't done with  
it.  This doesn't turn out to be hard in practice.

The general moral is that garbage collection is great for managing  
resources that are entirely inside the programming language runtime,  
e.g. non-shared memory, but not great for managing resources that  
have to be shared with things outside of the programming language  
runtime, e.g. files.



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