[issue4258] Use 30-bit digits instead of 15-bit digits for Python integers.

[STINNER Victor]

STINNER Victor <victor.stinner at haypocalc.com> added the comment:

> Note that to avoid "bad marshal data" errors, 
> you'll probably need to do a 'make distclean' 
> before rebuilding with this patch.

I saw that you choosed to use the base 2^30 for marshal. For a better 
portability (be able to use .pyc generated without your patch), you 
may keep the base 2^15. I implemented that in my GMP patch (manual 
conversion from/to base 2^15).

If we change the marshal format of long, the magic number should be 
different (we might use a tag like the "full unicode" tag used in 
Python3 magic number) and/or the bytecode (actual bytecode is 'l'). 
The base should be independent of the implementation, like Python does 
with text: UTF-8 for files and UCS-4 in memory. We may use the base 
2^8 (256) or another power or 2^8 (2^16, 2^32, 2^64?). The base 256 
sounds interresting because any CPU is able to process 8 bits digits.

Cons: Use a different bases makes Python slower for loading/writing 
from/to .pyc.

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nosy: +haypo

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<http://bugs.python.org/issue4258>
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