https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81515
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- This is expected. Gcc has a warning for undefined identifiers used in #if. In standard C preprocessor language undefined identifiers used in #if is converted into the literal 0. This has been part of the language since C90 (or even before).