On Sun, 2018-12-30 at 18:50 +0100, LEROY Christophe wrote: > Arnd Bergmann <arnd@xxxxxxxx> a écrit : > > On Sat, Dec 29, 2018 at 3:51 AM Michael Schmitz > > <schmitzmic@xxxxxxxxx> wrote: [...] > > > (On second thought - I don't want to speculate whether there's > > > weird compiler options that could result in the > > > nvram_check_checksum and nvram_read_bytes symbols to still be > > > referenced in the final link, even though > > > IS_BUILTIN(CONFIG_NVRAM) always evaluates to false. Best > > > leave this as-is.) > > > > As far as I know, it's totally reliable with the supported > > compilers (gcc-4.6+). In the older compilers (e.g. 4.1), there was > > a corner case, where it could have failed to eliminate a function > > that was only referenced through a pointer from a discarded > > variable, but a plain IS_ENABLED() check like the one here > > was still ok, and lots of code relies on that. > > > > Other than that, I agree either way is totally fine here, so no > > objections to using the #ifdef. > > As far as I know, kernel codying style promotes the use of > IS_ENABLED() etc. instead of #ifdefs when possible. It's a preference, as with a lot of coding style stuff, which we leave up to the maintainer. That said, as has been pointed out, the current #ifdef has a failing corner case when both are modular (because the code should then be included). The runtime macro that correctly expresses this is IS_REACHABLE(CONFIG_NVRAM). James
