likely, unlikely and builtin_expect()

[Diego Woitasen <diego@xxxxxxxxxxxxxxx>]

I understand the meaning of likely() and unlikely() in linux/compiler.h,
but I don't undertand the meaning of !! in the definition.

#define likely(x)       __builtin_expect(!!(x), 1)
#define unlikely(x)     __builtin_expect(!!(x), 0)

why not this?:

#define likely(x)       __builtin_expect((x), 1)
#define unlikely(x)     __builtin_expect((x), 0)


thanks...



-- 
Diego Woitasen <diego@xxxxxxxxxxxxxxx>


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