OT the spirit of Spirit

[Mark Wieder]

Doug-

My favorite story concerning the Mars projects involves Wind River's
OS and debugging. NASA has a policy of "test what you fly and fly what
you test", which involves, among other things, leaving your debugging
code in place. There's a lesson to be learned here:

http://www.kohala.com/start/papers.others/pathfinder.html

"VxWorks contains a C language interpreter intended to allow
developers to type in C expressions and functions to be executed on
the fly during system debugging. The JPL engineers fortuitously
decided to launch the spacecraft with this feature still enabled. By
coding convention, the initialization parameter for the mutex in
question (and those for two others which could have caused the same
problem) were stored in global variables, whose addresses were in
symbol tables also included in the launch software, and available to
the C interpreter. A short C program was uploaded to the spacecraft,
which when interpreted, changed the values of these variables from
FALSE to TRUE. No more system resets occurred."

-- 
-Mark Wieder
 mwieder at ahsoftware.net