Until a few years ago you could still find K&R declarations in the Ruby source code[1]. Wasn't until 1.9 that they switched things over to ANSI style, iirc.
So, believe it or not, you might still find it out there in the wild.
FreeBSD still uses this declaration style liberally (keep in mind FreeBSD is a fork of BSD which has been around for some decades, and it makes sense that there's some old code floating around in the kernel)
So, believe it or not, you might still find it out there in the wild.
[1] eg: https://github.com/ruby/ruby/blob/v1_8_7_374/compar.c