Re: [PATCH] static_call: fix function type mismatch

From: Steven Rostedt
Date: Mon Mar 22 2021 - 15:33:19 EST

On Mon, 22 Mar 2021 18:06:37 +0100
Arnd Bergmann <arnd@xxxxxxxxxx> 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 the function to return 'int' as well, but remove the cast to
> ensure we get a warning if any of the types ever change.

I think the answer is the other way around. That is, to make the functions
it references return long instead. __static_call_return0 is part of the
dynamic call infrastructure. Perhaps it is currently only used by functions
that return int, but what happens when it is used for a function that
returns a pointer?

-- Steve

> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---