[Python-Dev] String interning

[Oren Tirosh]

On Mon, Jul 01, 2002 at 09:03:22AM +0200, Martin v. Loewis wrote:
> Oren Tirosh <oren-py-d@hishome.net> writes:
> 
> > In stringobject.c most references to ob_sinterned are to initialize it. The
> > only place that uses it is string_hash:  if ob_sinterned is not NULL it uses 
> > the hash of the string it points to instead of the current string object. 
> 
> This is not true: PyString_InternInPlace has

I meant references to ob_sinterned outside the actual implementation of 
PyString_InternInPlace.

> > Summary: As far as I can tell, indirectly interned strings are redundant. 
> > Without them the ob_sinterned field is effectively a boolean flag.
> > 
> > Can anyone explain why interning is implemented the way it is?  Can anyone
> > explain why Mac/Python/macimport.c is messing with ob_sinterned?
> 
> I'm not sure what meaning you would assiocate with the boolean
> flag. 

"This string is interned. It is equal to another interned strings iff they 
are the same object"

...
> If that code prints "reinterning", it can efficiently intern the
> argument, but couldn't with your change.
> 
> I agree that this is very rare, but in the test suite, it triggers 5
> times in test_descr.

test_descr is not exactly typical Python code...  

What bothers me is that of the two places that check if a string is interned 
one is a no-op and the other never happens.

	Oren