Why glibc's fstat() is slow

I mean, they didn’t realize it was slower.

Simpler code is a net good, freeing up time and making bugs less likely, and if you can get it without trade offs, you should do it. It seems reasonable to believe the perf would be ~the same, which they did.

So maybe they need better testing but they didn’t do anything *wrong* and certainly didn’t knowingly prioritize convenience over performance.