From: David Laight <david.laight.linux@gmail.com>
To: WangYuli <wangyuli@uniontech.com>
Cc: Matthew Wilcox <willy@infradead.org>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, yuzhao@google.com,
stevensd@chromium.org, kaleshsingh@google.com,
zhanjun@uniontech.com, niecheng1@uniontech.com,
guanwentao@uniontech.com
Subject: Re: [PATCH] mm: vmscan: Avoid signedness error for GCC 5.4
Date: Wed, 7 May 2025 21:46:16 +0100 [thread overview]
Message-ID: <20250507214616.4d91620e@pumpkin> (raw)
In-Reply-To: <FF9F758FB6DEBA6B+668772f9-2604-4035-bb04-b59eabf9bbd3@uniontech.com>
On Wed, 7 May 2025 10:55:31 +0800
WangYuli <wangyuli@uniontech.com> wrote:
> Hi Matthew Wilcox and Andrew Morton,
>
> On 2025/5/7 00:22, Matthew Wilcox wrote:
> > 1. This has nothing to do with the compiler version; the type-checking
> > is built into min().
>
> Thank you for pointing that out! My previous statement was incorrect.
>
> The error is actually from the __types_ok check within the
> __careful_cmp_once macro failing, which triggered BUILD_BUG_ON.
>
> But then, why do newer compilers compile this without error? Is it
> perhaps because they consider 4U - 1 to be signed?
No, statically_true(tier >= 0) is true even though 'tier' is signed
because the compiler has inlined the function and followed the domain
of 'tier' from the assignments and loops.
David
next prev parent reply other threads:[~2025-05-07 20:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-06 16:02 WangYuli
2025-05-06 16:22 ` Matthew Wilcox
2025-05-07 2:55 ` WangYuli
2025-05-07 20:46 ` David Laight [this message]
2025-05-07 12:06 ` David Laight
2025-05-06 23:24 ` Andrew Morton
2025-05-07 4:06 ` WangYuli
2025-05-07 18:07 ` Andrew Morton
2025-05-07 20:49 ` Matthew Wilcox
2025-05-10 10:24 ` David Laight
2025-05-15 15:11 ` WangYuli
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