Protect prefetch macro arguments.
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From: Linus Torvalds on 26 Mar 2010 17:10 On Fri, 26 Mar 2010, David Daney wrote: > > The GCC built-in __builtin_prefetch() is a vargs function. If we > don't wrap the macro parameter in parentheses, a comma operator in the > actual argument list might cause unintended parameters to be passed to > __builtin_prefetch(). This seems totally pointless and actively wrong. You cannot have a comma operator in the actual argument list to the #define, because if you did, then you'd get a macro "prefetch()" passed 2 arguments, but takes just 1 so the only way I see to pass a comma operator is to _already_ have the macro parameter in parenthesis. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Linus Torvalds on 26 Mar 2010 17:30 On Fri, 26 Mar 2010, David Daney wrote: > On 03/26/2010 02:04 PM, Linus Torvalds wrote: > > > > > > On Fri, 26 Mar 2010, David Daney wrote: > > > > > > The GCC built-in __builtin_prefetch() is a vargs function. If we > > > don't wrap the macro parameter in parentheses, a comma operator in the > > > actual argument list might cause unintended parameters to be passed to > > > __builtin_prefetch(). > > > > This seems totally pointless and actively wrong. > > Pointless, perhaps. But 'actively wrong'? Are you sure about that? Yes, I'm sure about that. Your commit message was actively misleading, and the end result is worse than the original and shows a lack of understanding of the C preprocessor. IOW, very much "actively wrong". Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: David Daney on 26 Mar 2010 17:40
On 03/26/2010 02:04 PM, Linus Torvalds wrote: > > > On Fri, 26 Mar 2010, David Daney wrote: >> >> The GCC built-in __builtin_prefetch() is a vargs function. If we >> don't wrap the macro parameter in parentheses, a comma operator in the >> actual argument list might cause unintended parameters to be passed to >> __builtin_prefetch(). > > This seems totally pointless and actively wrong. Pointless, perhaps. But 'actively wrong'? Are you sure about that? In any event I guess I don't care much one way or the other. I was working on something else when I saw this. It looked wrong to me. Thanks, David Daney > > You cannot have a comma operator in the actual argument list to the > #define, because if you did, then you'd get a > > macro "prefetch()" passed 2 arguments, but takes just 1 > > so the only way I see to pass a comma operator is to _already_ have the > macro parameter in parenthesis. > > Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |