FreeBSD uses _Generic() in its system headers, and is within its rights to do so.
@@ -1710,7 +1710,6 @@ if test "x$enable_gcc_warnings_advisory" != "xno"; then
-Wbool-conversion
-Wbool-conversions
-Wbuiltin-requires-header
- -Wc11-extensions
-Wc99-c11-compat
-Wchar-align
-Wcompare-distinct-pointer-types
Nick Mathewson