lukeadamson | 3 years ago | on: My Hardest Bug Ever (2013)
lukeadamson's comments
lukeadamson | 3 years ago | on: My Hardest Bug Ever (2013)
One of my favorites:
I was working a large project for a wafer fab company, and occasionally the compiler would crash during full builds with SIGILL (illegal instruction, for those who aren’t familiar with the signal). Compiler bugs are never fun, and this was particularly vexing because it was so inconsistent.
It took me awhile, but eventually I got around to thinking: What could cause the compiler to execute an illegal instruction? What could cause an illegal instruction at all?
I removed the outer case from my computer, and sure enough, all of the fans had died. The CPU was overheating during intense, long-running builds. Replaced the fans and the “bug” went away!
*This is my first comment since I created my account in 2009. I hope I did it right! ;-)
page 1
Once upon a time, we got a panicked email from a customer whose OmniOutliner file would no longer open. He’d written a novel in it and was understandably keen to not lose his work.
Sure enough, when we opened his file with the debugger attached, it crashed immediately. Curiously, the crash was deep inside Apple’s XML parsing code, which we used indirectly by saving the file in their XML-variant of a property list.
Looking at the file in a text editor, we eventually found a funny-looking character where there should’ve been an angle bracket (an opening or closing bracket of an XML element). Inspecting it in a hex editor revealed that the difference between the actual character and what it should’ve been was precisely one bit.
How on Earth could that happen?! A bit more sleuthing (haha) uncovered more of these aberrations, and it didn’t take long before we realized that they occurred at regular intervals.
We patched it up, emailed it back to the customer, and suggested he check his RAM. He soon replied, thanking us but then asking, “How did you know I had bad RAM from my novel?!”