[Python-Dev] Bytcode "magic tag"

Eric V. Smith eric at trueblade.com
Wed Oct 28 10:24:30 EDT 2015


On 10/28/2015 10:19 AM, Barry Warsaw wrote:
> On Oct 28, 2015, at 08:35 AM, Eric V. Smith wrote:
> 
>> The "following table" is a comment, that contains a few references to
>> the tag "cpython-<version>", specifically cpython-32. It doesn't seem
>> that the tag is routinely updated in the comment.
> 
> IIRC, it used to have to be changed in the code, but with this...
> 
>> sys.implementation.cache_tag returns 'cpython-36', and is in fact
>> implemented as 'cpython-{PY_MAJOR_VERSION}{PY_MINOR_VERSION}'.
> 
> ...I don't believe it does any more.

Okay. Maybe I'll update that comment, then.

>> Unlike what the comment in _boostrap_external.py suggests, this "magic tag"
>> will not change every time a bytecode is added, but only on every minor
>> release. Which implies that if we have a micro release that adds an opcode,
>> we'll in fact break the promise in the comment.
> 
> Right.  Have we ever done that though?  We shouldn't!

And maybe I'll add that to the updated comment!

Eric.



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