My First Clang Bug

Part of the role of being a packager is compiling lots (and lots) of packages. That means compiling lots of code from interesting places and in a variety of styles. In my opinion, being a good packager also means providing feedback to upstream when things are bad. That means filing upstream bugs when possible, and upstreaming patches.

One of the “exciting” moments in packaging is when tools change. So each and every major CMake update is an exercise in recompiling 2400 or more packages and adjusting bits and pieces. When a software project was last released in 2013, adjusting it to modern tools can become quite a chore (e.g. Squid Report Generator). CMake is excellent for maintaining backwards compatibility, generally accomodating old software with new policies. The most recent 3.12 release candidate had three issues filed from the FreeBSD side, all from fallout with older software.  I consider the hours put into good bug reports, part of being a good citizen of the Free Software world.

My most interesting bug this week, though, came from one line of code somewhere in Kleopatra:

Q_UNUSED(gpgagent_data);

That one line triggered a really peculiar link error in KDE’s FreeBSD CI system. Yup .. telling the compiler something is unused made it fall over. Commenting out that line got rid of the link error, but introduced a warning about an unused function. Working with KDE-PIM’s Volker Krause, we whittled the problem down to a six-line example program — two lines if you don’t care much for coding style. I’m glad, at that point, that I could throw it over the hedge to the LLVM team with some explanatory text. Watching the process on their side reminds me ever-so-strongly of how things work in KDE (or FreeBSD for that matter): Bugzilla, Phabricator, and git combine to be an effective workflow for developers (perhaps less so for end-users).

Today I got a note saying that the issue had been resolved. So brief a time for a bug. Live fast. Get squashed young.