[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] RE: [PATCH]enable PCI serial card usage
On Wednesday, 2010-3-31 5:09 PM, Keir Fraser wrote: > On 31/03/2010 03:40, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote: > >> + int pb_bdf_enable:1; /* if =1, pb-bdf effective, port behind >> bridge */ + int ps_bdf_enable:1; /* if =1, ps_bdf effective, >> port on pci card */ > > Point of information for you: a signed integer N-bit bit field can > take values in the range -2^(N-1) to 2^(N-1)-1. In this case N=1 and > the allowed values are -1 and 0. Hence assigning value 1 to the above > bit fields has undefined behaviour and some versions of gcc will not > 'set the flag' as you expect! We've been bitten by it before. > Generally your bit fields should be *unsigned* unless you > specifically want signed-integer semantics. Even better here, we'll > burn the extra bits and use xen_bool_t. > > I will fix your patch in this case before applying. Thanks for point it out. xen_bool_t would be safer for such case. Jimmy _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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