[Python-Dev] RE: [Zope-Coders] core dump in Zope 2.7 test suite

[Martin v. Löwis]

Jeremy Hylton <jeremy at zope.com> writes:

> > Still, it doesn't look to me like the code *expected* that str could contain
> > uninitialized heap trash at this point, so I'd like someone who thinks they
> > understand this code to think about how that could happen (it apparently is
> > happening, so "beats me" isn't good enough <wink>).
> 
> I certainly don't understand the code yet.

The code you quote is about the "singleton" Unicode character
(i.e. those with code points < 256). If you create a Unicode object S
with len(S)==1, and ord(S) < 256, you don't necessarily get a new
object, but you may get an existing (cached) one. If you then apply
PyUnicde_Resize to that object, you get an error because resizing that
object would require changing all shared copies, which is bad because
Unicode object are immutable.

I agree with Tim that, in no case, resize should be called for a
garbage string - only valid strings (i.e. with truly allocated memory)
should ever be resized.

Regards,
Martin