The file that was never in the build

Spent longer than I would like today working out why a change to Booth, my GPU compiler, was doing precisely nothing. Edit the file, rebuild, run it, no difference. Do it again, slower. Still nothing.

The file was never in the build. Not excluded, not a stale object lying around, just never wired in to begin with. And I wrote it. Every line, months ago, at what the timestamps suggest was about 3am, which tracks.

The galling part is that everything compiled and passed the whole time without it, so nothing ever complained. Wired it in properly, reran the tests, all still green. Which means it was genuinely dead code I had been mentally counting as part of the compiler this entire time.

Lesson filed: check the build actually builds what you think it builds. Even when you are the one who wrote the build.