Re: [PATCH] [v2] static_call: fix function type mismatch

From: Peter Zijlstra
Date: Tue Mar 23 2021 - 03:35:03 EST

On Mon, Mar 22, 2021 at 10:42:24PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> The __static_call_return0() function is declared to return a 'long',
> while it aliases a couple of functions that all return 'int'. When
> building with 'make W=1', gcc warns about this:
> kernel/sched/core.c:5420:37: error: cast between incompatible function types from 'long int (*)(void)' to 'int (*)(void)' [-Werror=cast-function-type]
> 5420 | static_call_update(might_resched, (typeof(&__cond_resched)) __static_call_return0);
> Change all these function to return 'long' as well, but remove the cast to
> ensure we get a warning if any of the types ever change.

I still think it's utter batshit.

Please explain which architecture ABI is affected and why the warning is