On Wed, Sep 25, 2019 at 9:14 AM Ard Biesheuvel
[off-list ref] 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.

             Linus

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