[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] question regarding gnu-isms
Aron Griffis wrote: Hi Anthony, Thanks for the explanation of the struct initialization. Regarding the second one, though... Anthony Liguori wrote: [Thu Apr 27 2006, 07:04:01PM EDT]Aron Griffis wrote:#define xen_create_contiguous_region(vstart, order, address_bits) ({0;})This is a really common one that lets you make statements into expressions....#define min(a, b) ({int lhs = a; int rhs = b; (lhs < rhs) ? lhs : rhs;})That makes sense for the example you gave, but how does it apply to the definition in question? Is there any difference between ({0;}) and (0) or even 0? Can you point me to where you saw this (and in what version of Xen)?There is no difference between (0) and 0 of course. I don't *think* there's a difference between ({0;}) and (0) but of course I've seen stranger things before. My guess is that it started it's life as a more complex set of statements and overtime was reduced to just that. Regards, Anthony Liguori All of these are documented in the GCC Info page (see the section on C Extensions).:-) I read that before posting, so I was familiar with the purpose of enclosing compound statements in expressions. But I'll reread in case there's something I missed regarding the interpretation of ({0;}) Regards, Aron _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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