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Date:   Fri, 8 Aug 2014 00:20:38 +0200
From:   Ralf Baechle <ralf@linux-mips.org>
To:     Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc:     Jeffrey Deans <jeffrey.deans@imgtec.com>,
        Markos Chandras <markos.chandras@imgtec.com>,
        linux-mips@linux-mips.org
Subject: Re: [PATCH 7/7] MIPS: GIC: Fix GICBIS macro
Message-ID: <20140807222038.GF29898@linux-mips.org>
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On Fri, Jul 18, 2014 at 10:05:29PM +0400, Sergei Shtylyov wrote:

> >>>+#define GICBIS(reg, mask, bits)            \
> >>>+    do { u32 data;                \
> >>>+        GICREAD((reg), data);        \
> 
> >>    Why () only around 'reg', not around 'data'?
> 
> >Brackets aren't necessary around "data" because it is declared at the start of
> >the "do" code block, so it can't expand to anything else within that scope.
> 
>    Oh, I was not attentive enough, sorry about that... :-<
>    However, it makes sense to at least put that declaration at a separate line.

And it's not safe against multiple evaluation of macro arguments.  Imagine
what's going to happen if GICBIS is called as something like

	GICBIS(++a, ++b, c);

That'll expand to:

    do { u32 data;
            GICREAD((++a), data);
            data &= ~(++b);
            data |= ((bits) & (++b));
            GICWRITE((++a), data);
    } while (0)

Paranoia?

  Ralf