It is actually valid in ANSI C89 too, although it does look rather odd to those accustomed to seeing the types.<p><a href="http:&#x2F;&#x2F;stackoverflow.com&#x2F;questions&#x2F;5885156&#x2F;no-defined-type-of-a-function-parameter-defaults-to-int-am-i-insane" rel="nofollow">http:&#x2F;&#x2F;stackoverflow.com&#x2F;questions&#x2F;5885156&#x2F;no-defined-type-o...</a>