This check dates to pretty early - I found it in 28e62ed68c5d23605edd73c4267789b2af0b5c09, from 2004. I checked, and this was only true in OS X 10.0 through 10.2. With the version of libc available in OS X 10.3 and newer, getopt.h exists like on Linux and has to be included to get what adplay expects to be there. I'm guessing there's a good chance adplay won't compile on OS X 10.0 through 10.2 these days anyway.
This and #28 got adplay-unix building for me on current versions of macOS.
This check dates to pretty early - I found it in 28e62ed68c5d23605edd73c4267789b2af0b5c09, from 2004. I checked, and this was only true in OS X 10.0 through 10.2. With the version of libc available in OS X 10.3 and newer,
getopt.hexists like on Linux and has to be included to get what adplay expects to be there. I'm guessing there's a good chance adplay won't compile on OS X 10.0 through 10.2 these days anyway.This and #28 got adplay-unix building for me on current versions of macOS.