On Wednesday, April 15, 2020 at 6:49:15 AM UTC-7, Peter Flass wrote:
>
> I wonder how long it took to discover this
>
I don't know how much time the user spent creating the test program that isolated the error, but I from the size and complexity of it, I would hazard at least several days.
When I received a copy of that program, I was able to use the tools that I had build into the emulator to track instructions and data at a sub-instruction level. It took maybe an hour of analysis understand the data flow from the comamand line parameter to the high bits of the LPRP operand.
In retrospect, the process took longer because I was assuming that there was an error in the emulator and I spent too much time looking carefully at code that was correct. If I had started by reviewing the documentation for the LPRP instruction, I would have immediately seen that the fault would only be caused by the two high bits being set, then would have looked at the source of the user's code and seen how the stack memory was initialized; persumably I would have worked it out with having to run any tests. There have been so many bugs in the code that I have a conditioned response.
-- Charles