Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 24 Mar 2020 09:33:21 -0700 | Subject | Re: [RESEND][PATCH v3 14/17] static_call: Add static_cond_call() |
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On Tue, Mar 24, 2020 at 9:22 AM Andy Lutomirski <luto@amacapital.net> wrote: > > I haven’t checked if static calls currently support return values, but > the conditional case only makes sense for functions that return void. > > Aside from that, it might be nice for passing NULL in to warn or bug > when the NULL pointer is stored instead of silently NOPping out the > call in cases where having a real implementation isn’t optional.
Both good points. I take back my question.
And it aside from warning about passing in NULL then it doesn't work, I wonder if we could warn - at build time - when then using the COND version with a function that doesn't return void?
Of course, one alternative is to just say "instead of using NOP, use 'xorl %eax,%eax'", and then we'd have the rule that a NULL conditional function returns zero (or NULL).
I _think_ a "xorl %eax,%eax ; retq" is just three bytes and would fit in the tailcall slot too.
Linus
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