https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86668
Andreas Schwab <sch...@linux-m68k.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #1 from Andreas Schwab <sch...@linux-m68k.org> --- Please use gcc-h...@gcc.gnu.org for user questions. With the prototype in scope the non-prototyped definition of fun is adjusted. This doesn't happen if the prototype is no longer in scope. If you want defined behaviour you need to use the correct prototype with the argument declared as double.