The documentation for NSFileManager contains this curious statement:

> In Mac OS X v 10.5 and later you should consider using [[NSFileManager alloc] 
> init] rather than the singleton methoddefaultManager. Instances of 
> NSFileManager are considered thread-safe when created using [[NSFileManager 
> alloc] init].

This makes me wonder:

1. Why are the additional instances only "considered" thread-safe. Doesn't 
anyone know?

2. What does "thread-safe" mean in this context? I would take it to mean that 
*any* single instance allocated with [[NSFileManager alloc] init] can be used 
by *any* thread. Or does it mean that each thread needs a unique instance, but 
such instances happily co-exist?

3. If any single instance allocated with [[NSFileManager alloc] init] is 
thread-safe in the fullest sense, why doesn't [NSFileManager defaultManger] 
just return one of these, so that it can be (considered) thread-safe too?

The Leopard release notes don't shed much light.

I did find this thread from 2008:

        
http://www.omnigroup.com/mailman/archive/macosx-dev/2008-June/061392.html

which appears to say the documentation is wrong. It appears to say that 
instances are not thread-safe, but can safely be used by one thread at a time.

I also found this in the Threaded Programming Guide:

> Thread-Safe Classes
> 
> The following classes and functions are generally considered to be 
> thread-safe. You can use the same instance from multiple threads without 
> first acquiring a lock.
> 
>       [...]
>       • NSFileManager (in Mac OS X v10.5 and later)


which contradicts that thread.

Anyone in the know got confirmation/answers on this? (I only care about 10.5 
and later.)


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