linux-kernel - Re: [PATCH] Documentation: Explain a second alternative for multi-line macros.

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Date:	Mon, 1 Jan 2007 16:37:20 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Randy Dunlap <randy.dunlap@...cle.com>
cc:	Segher Boessenkool <segher@...nel.crashing.org>,
	"Robert P. J. Day" <rpjday@...dspring.com>,
	Muli Ben-Yehuda <muli@...ibm.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	trivial@...nel.org
Subject: Re: [PATCH] Documentation: Explain a second alternative for multi-line
 macros.


On Dec 31 2006 19:23, Randy Dunlap wrote:
>> > 
>> > #define setcc(cc) ({ \
>> > partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3); \
>> > partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3); })
>> 
>> This _does_ return a value though, bad example.
>
> Where does it return a value?  I don't see any uses of it
> in arch/i386/math-emu/* that use it as returning a value.
>
> And with a small change to put it inside a do-while block
> instead of ({ ... }), it at least builds cleanly.
> I expected some complaints.

If people want to return something from a ({ }) construct, they should do it
explicitly, e.g.

#define setcc(cc) ({ \
	partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3); \
	partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3); \
	partial_status; \
})


	-`J'
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