I'd also look more favorably on and be more likely to recommend
toolchains that implement broadly-used industry extensions. :)

By "broadly-used industry extensions" you mean "gcc extensions" I guess?

I did a quick test using some other C compilers I have, SunStudio 11/12, Keil uVision 5, VisualStudio 2015, and none of them accepts the "..." extension to the case labels in switch statements, at least not out of the box, so I would hardly call that "broadly-used industry extensions".

To be fair, I did find that SunStudio 12 Update 1 appears to have introduced this.

I might file an RFE for this ;)

Andy

/Thomas