finnw writes "Research scientist Chris Lomont has analyzed in depth the Excel 2007 "65535" bug. Summary from the article:
This note:One interesting point is that the affected routine appears to be written in x86 assembly language. Fortunately it doesn't appear to have caused a security hole."
- details how the bug works,
- shows the bug is a rendering bug, not a math error as many reported,
- shows how it was likely introduced by comparison to Excel 2002 and Excel 2000 behavior (the bug seems to have been inserted when updating an older 16-bit formatting routine to a 32-bit equivalent),
- explains how the just released hotfix corrects the behavior, confirming the analysis of the bug,
- and demonstrates why exactly twelve values out of more than 9*10^18 (approx 2^63) possible 64-bit floating-point values suffer from this bug.