using sizeof operator

using sizeof operator

[Sukrit Sangwan]

There are instances in the code where sizeof(*ptr) is used. e.g.
in net/802/garp.c
          const struct garp_msg_hdr *gm;
          if (!pskb_may_pull(skb, sizeof(*gm)))
 return -1;
i want to ask is there any sense in using sizeof(struct garp_msg_hdr)
instead of sizeof(*gm) in the above example.

Thanks
--
Sukrit Sangwan
IIT Roorkee
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using sizeof operator

[Daniel Baluta]

On Sun, Jan 22, 2012 at 8:14 PM, Sukrit Sangwan <sukritsangwan@gmail.com> wrote:
> There are instances in the code where sizeof(*ptr) is used. e.g.
> in net/802/garp.c
> ? ? ? ? ? const struct garp_msg_hdr *gm;
> ? ? ? ? ? if (!pskb_may_pull(skb, sizeof(*gm)))
> ?return -1;
> i want to ask is there any sense in using sizeof(struct garp_msg_hdr)
> instead of sizeof(*gm) in the above example.

Imagine what would happen if you change the name of struct garp_msg_hdr;

thanks,
Daniel.

using sizeof operator

[Daniel Baluta]

On Sun, Jan 22, 2012 at 10:17 PM, Sukrit Sangwan
<sukritsangwan@gmail.com> wrote:
> I found an instance where sizeof(struct xyz) is used instead of
> sizeof(variablename).
> I want to ask if it would be appropriate to contact the author about the
> same.

Well, this doesn't really matter, but the recommended practice is to use
sizeof(*pointer);

Please keep intact Cc's list.

thanks,
Daniel.

using sizeof operator

[Sukrit Sangwan]

also i want to ask why not use simply 8 instead of sizeof(u8).

-- 
Sukrit Sangwan
IIT Roorkee
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using sizeof operator

[Jonathan Neuschäfer]

On Sun, Jan 22, 2012 at 11:58:30PM +0530, Sukrit Sangwan wrote:
> also i want to ask why not use simply 8 instead of sizeof(u8).

That would be 1 most of the time. sizeof returns the size in bytes
(according to the C reference manual in K&R's book).

Apart from that, sizeof(u8) is more explicit about the intention.

HTH,
	Jonathan Neusch?fer

using sizeof operator

[Bernd Petrovitsch]

On Son, 2012-01-22 at 23:58 +0530, Sukrit Sangwan wrote:
> also i want to ask why not use simply 8 instead of sizeof(u8).

Because it is wrong.

	Bernd
-- 
Bernd Petrovitsch                  Email : bernd at petrovitsch.priv.at
                     LUGA : http://www.luga.at