European Space Agency
An overflow occurred when converting a 16-bit number to a 64-bit numer in the Ariane 5 intertial guidance system, causing the rocket to crash. The actual overflow occurred in code that wasn’t necessary for operation but was running anyway. According to one account, this caused a diagnostic error message to get printed out, and the diagnostic error message was somehow interpreted as actual valid data. According to another account, no trap handler was installed for the overflow.
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