Re: [Xen-devel] [patch] double incrementing l2tab

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 12 May 2005, at 22:06, Scott Parish wrote:

> For PAE, l2e_get_phys() will look something like this:
>
>   #define l2e_get_phys(_x)          ((((u64)(_x).l2_hi & 0x0f) << 32)  
> |\
>                                       ((u64)(_x).l2_lo & PAGE_MASK))
>
> Thus l2e_get_phys(++foo) is not safe, as the increment will be 
> evaluated
> multiple times and at undefined times.
This leaves the macro to bite you in future. Either make l2e_get_phys() 
a static inline function, or do something like:
#define l2e_get_phys(_x) ({ \
    u64 __x = (_x); \
    <your macro here but _x -> __x>; \
})

 -- Keir


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