It’s just a one-line change!
Even the simplest of changes can cause unexpected regressions due to lurking problems.
In bug 81125, the upgrade regression had nothing to do with the content of the change that triggered it: any user who had installed the libpthread20 package would encounter a problem the next time libc6 was upgraded.
In bug 309674, the failure was a misbuild due to timestamp skew in the build process. The underlying problem existed in the source package in the original release, but would only manifest in a small percentage of builds.
Citizen, be paranoid, and expect the unexpected.
- Ubuntu wiki page on Stable Release Updates. These bugs had to be a PITA to debug.
