linux-kernel - Re: [PATCH v2] mm: kmalloc_index: make compiler break when size is not supported

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Message-ID: <YJlUyc8t7MoGTFTe@casper.infradead.org>
Date:   Mon, 10 May 2021 16:44:09 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: kmalloc_index: make compiler break when size is
 not supported

On Tue, May 11, 2021 at 12:02:30AM +0900, Hyeonggon Yoo wrote:
> @@ -382,8 +385,8 @@ static __always_inline unsigned int kmalloc_index(size_t size)
>  	if (size <=  8 * 1024 * 1024) return 23;
>  	if (size <=  16 * 1024 * 1024) return 24;
>  	if (size <=  32 * 1024 * 1024) return 25;
> -	if (size <=  64 * 1024 * 1024) return 26;
> -	BUG();
> +
> +	BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");

we're being encouraged to use static_assert() these days.
https://en.cppreference.com/w/c/language/_Static_assert