[1.7] bug in chdir

Wed Jul 15 18:50:00 GMT 2009

Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> I created a patch which uses WNetOpenEnum for the existence check, but
> it needs extremly long to timeout the existence check in such a case.

There's already a long timeout on unknown names; that's inescapable when 
dealing with // issues. Without the patch:
$ time dash -c 'cd //bin'
cd: 1: can't cd to //bin
real	0m6.921s
user	0m0.046s
sys	0m0.015s
$ time dash -c 'cd //home' # wrong result
real	0m0.187s
user	0m0.030s
sys	0m0.030s
$ time dash -c 'cd //eblake'
real 0m0.031s
user 0m0.030s
sys 0m0.015s
With the patch, I see:
$ time dash -c 'cd //bin'
cd: 1: can't cd to //bin
real 0m4.796s
user 0m0.030s
sys 0m0.030s
$ time dash -c 'cd //home' # right result
cd: 1: can't cd to //home
real 0m0.031s
user 0m0.030s
sys 0m0.015s
$ time dash -c 'cd //eblake'
real 0m0.031s
user 0m0.030s
sys 0m0.015s
So, no obvious speed regression on good paths, a whopping 25% performance 
improvement on paths that previously failed, and the desired failure on the 
questionable path is now achieved with speed comparable to the success path! 
I'd say go ahead and apply the patch - the numbers speak for themselves.
-- 
Eric Blake
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