Re: asm in C slightly OT

From: H. Peter Anvin (hpa@zytor.com)
Date: Sat Jul 22 2000 - 14:12:49 EST


Followup to: <39795FCE.65EE2768@pioneer.net>
By author: George Anzinger <george@pioneer.net>
In newsgroup: linux.dev.kernel
>
> The first line looks like a function proto type. It is unclear how it
> is related to the rest of the macro. This macro generates a bit of code
> that is not a function in any way. It has an entry label
> "common_interrupt" and ends with a jmp. What I really want to know is
> how to refer to a C variable inside of such a construct. The gcc
> documentation talks about how to do it in more standard asm. I would
> like, for example to add to the above macro, for example:
>
> "incl foo.bar" where bar is a member of structure foo.
>
> I know this could be done as: "incl foo+xxx" where xxx is the offset
> of bar in foo, but I would like the compiler to figure this for me so as
> to follow structure changes.
>

RTFM(info gcc)

  asm("incl (%0)" :: "i" (&foo.bar));

        -hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt

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