linux-kernel - Re: cleanup: Make no_free_ptr() __must

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Message-ID: <20230816091707.GA980931@hirez.programming.kicks-ass.net>
Date:   Wed, 16 Aug 2023 11:17:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: cleanup: Make no_free_ptr() __must_check

On Wed, Aug 16, 2023 at 08:00:17AM +0000, Linus Torvalds wrote:

> So I think it needs to be something like
> 
>   #define __get_and_free_ptr(p) \
>       ({ __auto_type __ptr = &(p); \
>          __auto_type __val = *__ptr; \
>          *__ptr = NULL;  __val; })
> 
>   static inline __must_check
>   const volatile void * __must_check_fn(const volatile void *val)
>   { return val; }
> 
>     #define no_free_ptr(p) \
>         ((typeof(p)) __must_check_fn(__get_and_free_ptr(p)))
> 
> the above is entirely untested. Of course.

That works and is *much* saner than the horrible thing I did.