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

[Randy Dunlap <randy.dunlap@oracle.com>]

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
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