Messages in this thread | | | Date | Sun, 31 Dec 2006 20:30:42 -0800 | From | Randy Dunlap <> | Subject | Re: [PATCH] Documentation: Explain a second alternative for multi-line macros. |
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Segher Boessenkool 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? > > partial_status |=
as I expected (or suspected). I also suspect that it wasn't intended, but this is old code and I wasn't around Linux when it was written, so I don't know about it for sure.
>> I don't see any uses of it > > Ah, that's a separate thing -- it returns a value, it's just > never used.
Ack.
>> And with a small change to put it inside a do-while block >> instead of ({ ... }), it at least builds cleanly. > > Well please replace it then, statement expressions should be > avoided where possible (to start with, they don't have well- > defined semantics).
We should probably avoid gcc extensions when possible.
I'll send a separate email for the patch.
-- ~Randy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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