[Python-Dev] importing .pyc-files generated by Python 1.5.2 in Python 1.6. Why not?

[Christian Tismer]

Guido van Rossum wrote:
> 
> >    3. Patch the 1.6 unmarshaller to support loading 1.5.2 .pyc files
> 
> I agree that this is the correct solution.
> 
> > No choice looks very attractive.  Adding a '|| (magic == 0x994e)' or
> > some such somewhere in the 1.6 unmarshaller should do the trick.
> > But I don't want to submit a patch, if God^H^HGuido thinks, this isn't
> > worth the effort. <wink>
> 
> That's BDFL for you, thank you. ;-)
> 
> Before accepting the trivial patch, I would like to see some analysis
> that shows that in fact all 1.5.2 .pyc files work correctly with 1.6.
> This means you have to prove that (a) the 1.5.2 marshal format is a
> subset of the 1.6 marshal format (easy enough probably) and (b) the
> 1.5.2 bytecode opcodes are a subset of the 1.6 bytecode opcodes.  That
> one seems a little trickier; I don't remember if we moved opcodes or
> changed existing opcodes' semantics.  You may be lucky, but it will
> cause an extra constraint on the evolution of the bytecode, so I'm
> somewhat reluctant.

Be assured, I know the opcodes by heart.
We only appended to the end of opcode space, there are no changes.
But I can't tell about marshal.

ciao - chris

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