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RE: [GIT] Networking

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  RE: [GIT] Networking David Laight <David.Laight@ACULAB.COM> - 2015-09-07 13:10 +0200
    Re: [GIT] Networking "Rustad, Mark D" <mark.d.rustad@intel.com> - 2015-09-08 19:00 +0200

#1220056 — RE: [GIT] Networking

From: Rustad, Mark D
...
> >> static int smp_ah(struct crypto_blkcipher *tfm, const u8 irk[16],
> >>                  const u8 r[3], u8 res[3])
> >
> > Expect that it looks like you are passing arrays by value,
> > but instead you are passing by reference.
> >
> > Explicitly pass by reference and sizeof works.
> 
> It depends on what you mean by works. It at least doesn't look so misleading when passing by reference
> and so works more as expected. The sizeof in either case will never return the size of the array. To
> have sizeof return the size of the array would require a typedef of the array to pass by reference. In
> some cases that could be the right thing to do.

Feed:
int bar(int (*f)[10]) { return sizeof *f; }
into cc -O2 -S and look at the generated code - returns 40 not 4.

	David

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#1220996

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> On Sep 7, 2015, at 4:02 AM, David Laight <David.Laight@ACULAB.COM> wrote:
> 
> Feed:
> int bar(int (*f)[10]) { return sizeof *f; }
> into cc -O2 -S and look at the generated code - returns 40 not 4.

Yes, indeed it does. And with clang too. I guess I was too easily discouraged when looking for a workable syntax some years ago. At the time I stopped when the typedef worked, which really just encapsulates this. I should have recognized that then. Thanks for making it all so clear.

--
Mark Rustad, Networking Division, Intel Corporation

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