On Wed, 25 Sep 2019 at 23:01, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Sep 25, 2019 at 9:14 AM Ard Biesheuvel > <ard.biesheuvel@xxxxxxxxxx> wrote: > > > > config ARCH_SUPPORTS_INT128 > > bool > > + depends on !$(cc-option,-D__SIZEOF_INT128__=0) > > Hmm. Does this actually work? > > If that "depends on" now ends up being 'n', afaik the people who > _enable_ it just do a > > select ARCH_SUPPORTS_INT128 > > and now you'll end up with the Kconfig erroring out with > > WARNING: unmet direct dependencies detected for ARCH_SUPPORTS_INT128 > > and then you end up with CONFIG_ARCH_SUPPORTS_INT128 anyway, instead > of the behavior you _want_ to get, which is to not get that CONFIG > defined at all. > > So I heartily agree with your intent, but I don't think that model > works. I think you need to change the cases that currently do > > select ARCH_SUPPORTS_INT128 > > to instead have that cc-option test. > > And take all the above with a pinch of salt. Maybe what you are doing > works, and I am just missing some piece of the puzzle. But I _think_ > it's broken, and you didn't test with a compiler that doesn't support > that thing properly. > I think you may be right. Instead, I'll add a separate CC_HAS_INT128 symbol with the $(cc-option) test, and replace occurrences of select ARCH_SUPPORTS_INT128 with select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 which is a slightly cleaner approach in any case.
