On Thu, Jun 4, 2020 at 4:56 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > Er? That's not what it looked like to me: > > #define IS_BUILTIN(option) __is_defined(option) > #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option)) > > But just to be sure, I just tested in with a real build: > > [ 3.242160] IS_ENABLED(TEST_UNDEF) false > [ 3.242691] __is_defined(TEST_UNDEF) false > [ 3.243240] IS_ENABLED(TEST_VALUE_EMPTY) false > [ 3.243794] __is_defined(TEST_VALUE_EMPTY) false > [ 3.244353] IS_ENABLED(TEST_VALUE_1) true > [ 3.244848] __is_defined(TEST_VALUE_1) true > > and nope, it only works with a defined value present. You are right, it follows the Kconfig logic, returning false for defined-but-to-0 too. We should probably add an `IS_DEFINED()` macro kernel-wide for this (and add it to the `coding-guidelines.rst` since `IS_ENABLED()` is mentioned there, with a warning not to mix it with `__is_defined()` which looks it was only intended as an implementation detail for `include/linux/kconfig.h`). CC'ing Masahiro by the way. Cheers, Miguel
