https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107405
--- Comment #15 from Maciej W. Rozycki <macro at orcam dot me.uk> --- If in older C standard versions such enums are invalid, then I think this should be a hard error rather than a silent ABI change for the code produced. Not all code out there will have sanity checks such as the Linux kernel does and things will break for people in a tough way (think a public header file defining an enumeration and objects linked that define data of such an enumeration type and have been built with different compiler versions).
