On Wed, May 28, 2014 at 3:45 AM, David Laight <david.lai...@aculab.com> wrote: > From: Cody P Schafer >> Rather manually specifying the size of the integer to be converted, key >> off of the type size. Reduces duplicate size info and the occurance of >> certain types of bugs (using the wrong sized conversion). > ... >> +#define be_to_cpu(v) \ >> + __builtin_choose_expr(sizeof(v) == sizeof(uint8_t) , v, \ >> + __builtin_choose_expr(sizeof(v) == sizeof(uint16_t), be16_to_cpu(v), \ >> + __builtin_choose_expr(sizeof(v) == sizeof(uint32_t), be32_to_cpu(v), \ >> + __builtin_choose_expr(sizeof(v) == sizeof(uint64_t), be64_to_cpu(v), \ >> + (void)0)))) > ... > > I'm not at all sure that using the 'size' of the constant will reduce > the number of bugs - it just introduces a whole new category of bugs.
Certainly, if you mis-size the argument (and thus have missized one of the variables containing the be value, probably a bug anyhow), there will be problems. I put this interface together because of an actual bug I wrote into the initial code of the hv_24x7 driver (resized a struct member without adjusting the be*_to_cpu() sizing). Having this "auto sizing" macro means I can avoid encoding the size of a struct field in multiple places. -- 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/
