From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Tue, 26 Oct 2010 19:12:14 -0700
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Subject: 5c ulong/vlong -> float64 bug
From: Russ Cox <rsc@swtch.com>
To: 9fans <9fans@9fans.net>, inferno-list@vitanuova.com
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For those people using 5c, I found a bug recently in the
conversion of ulong to float64.  The bug is that it's not
implemented at all; instead 5c uses the long to float64 code,
so converting 0x80000000 produces -2^31 not 2^31.
This matters in _v2d, which uses it to convert vlong to float64.
If the low 32 bits of the vlong have the high bit set,
the conversion ends up off by 2^32.

http://codereview.appspot.com/2726041 has a
straightforward but perhaps inefficient fix.

Russ