On 05/14/2013 04:13 PM, Dan Carpenter wrote: > On Tue, May 14, 2013 at 03:54:52PM +0800, Chen Gang wrote: >> > On 05/14/2013 03:14 PM, Dan Carpenter wrote: >>> > > On Tue, May 14, 2013 at 02:01:50PM +0800, Chen Gang wrote: >>>>> > >> > >>>>> > >> > HCF_MAX_NAME_LEN is 32, which may less than ''probe_rsp->rawData[1]'', >>>>> > >> > so need check the length when copy to ssid. >>>>> > >> > >>>>> > >> > Type of 'probe_rsp->rawData[1]' is 'hcf_8' which is 'unsigned char', >>>>> > >> > better to cast to 'unsigned int' firstly, and then cast to 'int'. >>> > > Why not cast directly to int? It's the same in the end. >>> > > >> > >> > For gcc under x86, it's the same in the end. >> > >> > But I am not quite sure whether all platforms gcc compilers can get the >> > correct result, so I use (int)(unsigned int) for 'unsigned char'. >> > It is always correct if: >> > only let 'signed' and 'unsigned' cast are in the same type. >> > only let type cast with the same 'signed' or 'unsigned'. >> > >> > In my memory (may during 2006 - 2007 years), for some C compilers, when >> > cast from 'unsigned char' to 'int' directly, they will let '0xff' to >> > '0xffffffff'. >> > > No. You're talking about sign expansion and it only applies to > signed variables. Perhaps the confusion is that char type can be > either signed or unsigned if the sign isn't specified. On x86 a > "char" is "signed char" but there are other arches where it is > "unsigned char". > OK, thanks, "it is only applies to signed variables", so I will send patch v3 to "cast directly to int". > Also that wouldn't work. Casting a signed char to unsigned int > would still result in sign expansion. It would need to be casted to > unsigned char first then to int. For our case, it is 'unsigned char', so (int)(unsigned int) for 'unsigned char' is always correct. ;) Thanks. -- Chen Gang Asianux Corporation _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
