I have to admit, it feels quite nice to finally write this post. My support for MC/DC in gcc was merged April 4th, followed by a couple of bug fixes. This post is just an announcement - I plan to some time later write a more detailed post on how it works and how to use it, and maybe one on MC/DC itself.
It has been a long project. I started working on it around the start of 2022, so it took a bit more than two calendar years from starting the work to the feature being merged, with mixed activity.
I ran into an interesting problem when adding support for Modified Condition/Decision Coverage (MC/DC) in gcc (a topic for a later post): how do you large scale test a new compiler feature? In this case, I wanted to figure out what kind of control flow graphs gcc could create, how particular graph shapes would interact with my changes, and if my assumptions actually held. Hand rolled examples took me quite far, but not to the point I was confident I didn’t miss anything.