From: Mikael Pettersson <mikpe@it.uu.se>
To: Schrober <franzschrober@yahoo.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: container-of Implementation
Date: Mon, 14 Jan 2013 13:22:11 +0100 [thread overview]
Message-ID: <20723.63603.114080.51605@pilspetsen.it.uu.se> (raw)
In-Reply-To: <1635127.Ytukyo95FQ@bentobox>
Schrober writes:
> Hi,
>
> I wondered why the container_of implementation is so complicated.
>
> #define container_of(ptr, type, member) ({ \
> const typeof( ((type *)0)->member ) *__mptr = (ptr); \
> (type *)( (char *)__mptr - offsetof(type,member) );})
>
> isn't the __mptr not unnecessary? Why not following version?
>
> #define container_of(ptr, type, member) \
> ((type *)((char *)(ptr) - offsetof(type, member)))
Compile-time type checking. The first version requires ptr to be
assignment-compatible with the type of the struct member, the second
version accepts random junk for ptr.
next prev parent reply other threads:[~2013-01-14 12:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-14 10:46 Schrober
2013-01-14 12:22 ` Mikael Pettersson [this message]
2013-01-14 12:23 ` Geert Uytterhoeven
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