[Python-Dev] Memory size overflows

[Scott Gilbert]

[Tim Peters]
> 
> I'll repeat that it's hard to do this correctly and quickly (c.f. earlier
> comments about the history of Python's subtly buggy attempts).
> 
[...]
> 
>         0x01ff *
>         0x00ff
>         ------
>       0000
>         00ff
>         0000
>           fe01
>       --------
>       0001fd01
>          ^ oops
> 

That was sloppy on my part.  Thanks for showing me my error.  (That's as
gracious as I can be while saying "D'Oh!" on the inside.  :-)

Clearly you know the long answer to this problem.  It could involve taking
the ugly expression I had and adding 3 more terms to see if it adds up to a
problem.  Or if all those integer multiplies make it less attractive than
just going to double, then taking the log2() of each operand and counting
the bits to see if there is a problem.  Or using the PyLong_* machinery. 
Or something similar.  And you've got your fast path past the test for the
common case, so it looks like you're just hesitant to make the big ugly
macro...








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