[vox] The real problem with Toyota acceleration!

Norm Matloff matloff at cs.ucdavis.edu
Tue Feb 23 10:43:06 PST 2010


When cars with ABS first came out, I refused to buy them, simply because
software glitches like this would be too easy to pop up.  I buy them
now, but only because it's almost impossible to find a car without them.

We've not heard the last of such problems.

Norm

On Tue, Feb 23, 2010 at 10:22:04AM -0800, Brian Lavender wrote:
> I couldn't help entertaining myself with the following. What if Toyota
> was using an 8-bit micro controller, and they were using a signed value
> to track the position of the accelerator? You press more and it adds to
> a vector. The problem strangely started occuring when Toyota started
> taking out the throttle cable on their vehicles. I own two Toyotas. One
> with a throttle cable, the other without (uses a sensor to detect
> throttle position).
> 
> Question is?
> 
> What is 127 + 1
> 
> Answer
> 
> -128
> 
> Ha! Ha! Maybe not so funny for the guy driving the car.
> 
> Sorry, I just had to share. ;-)
> 
> If only they had used SPARK/ADA!
> http://libre.adacore.com/libre/tools/spark-gpl-edition/
> 
> 
> #include <stdio.h>
> int main() {
>     char foo;
> 
>     foo = 127;
>     printf("The value is %d\n", (char)(foo + 1) );
> }
> 
> brian
> --
> Brian Lavender
> http://www.brie.com/brian/
> 
> "There are two ways of constructing a software design. One way is to
> make it so simple that there are obviously no deficiencies. And the other
> way is to make it so complicated that there are no obvious deficiencies."
> 
> Professor C. A. R. Hoare
> The 1980 Turing award lecture
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