From: Thomas Gleixner <tglx@linutronix.de>
To: Alexey Dobriyan <adobriyan@gmail.com>,
dennis@kernel.org, tj@kernel.org, cl@linux.com
Cc: linux-mm@kvack.org, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com
Subject: Re: [PATCH] x86/percpu: fix cast in __pcpu_cast_* macros
Date: Wed, 29 May 2024 09:54:33 +0200 [thread overview]
Message-ID: <87cyp59hom.ffs@tglx> (raw)
In-Reply-To: <c818d685-6609-450b-a695-44b5c57518a7@p183>
On Mon, May 27 2024 at 08:51, Alexey Dobriyan wrote:
> Fix compile failure
>
> this_cpu_add(*p, x = 1);
>
> kernel/test.c:7:29: error: lvalue required as left operand of assignment
> 7 | this_cpu_add(*p, x = 1);
> | ^
> arch/x86/include/asm/percpu.h:134:51: note: in definition of macro '__pcpu_cast_1'
> 134 | #define __pcpu_cast_1(val) ((u8)(((unsigned long) val) & 0xff))
>
>
> This pattern is almost always wrong:
>
> #define M(x) ((T)x)
>
> also because it can't be used with assignment expressions: cast makes
> left part of it non-lvalue and assignment to non-lvalue has to break
> compilation.
In principle I agree with the change itself, but I really don't see the
point for
this_cpu_add(*p, x = 1);
Even if C supports it, it's just nasty and tasteless.
Thanks,
tglx
prev parent reply other threads:[~2024-05-29 7:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-27 5:51 Alexey Dobriyan
[not found] ` <81264b6c-fd23-2ee5-52cd-249047e317a7@linux.com>
2024-05-28 20:49 ` Dennis Zhou
2024-05-29 7:54 ` Thomas Gleixner [this message]
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