On Fri 06-09-13 08:56:45, Chris Metcalf wrote: > The macrology in cmpxchg.h was designed to allow arbitrary pointer > and integer values to be passed through the routines. To support > cmpxchg() on 64-bit values on the 32-bit tilepro architecture, we > used the idiom "(typeof(val))(typeof(val-val))". This way, in the > "size 8" branch of the switch, when the underlying cmpxchg routine > returns a 64-bit quantity, we cast it first to a typeof(val-val) > quantity (i.e. size_t if "val" is a pointer) with no warnings about > casting between pointers and integers of different sizes, then cast > onwards to typeof(val), again with no warnings. If val is not a > pointer type, the additional cast is a no-op. We can't replace the > typeof(val-val) cast with (for example) unsigned long, since then if > "val" is really a 64-bit type, we cast away the high bits. Ah, I see. Thanks for explanation.
Honza -- Jan Kara <j...@suse.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/