On Wed, Apr 11, 2012 at 5:09 AM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> On Wed, Apr 11, 2012 at 03:14:37AM -0600, Jim Cromie wrote:
>> My larger goal was to find use-cases for this:
>> (sent to LKML a day or 2 ago)
>>
>> +/**
>> + * BUILD_BUG_DECL - check declared objects
>> + * @name: distinguishes multiple uses at same scope.
>> + * @cond: false expr, typically like sizeof(a) != sizeof(b)
>> + *
>> + * This works at file-scope too, and supports checks like:
>> + * BUILD_BUG_DECL(foo, sizeof(a) != sizeof(b));
>> + * BUILD_BUG_DECL(id_strings, ARRAY_SIZE(id_strings) != ARRAY_SIZE(id_vals));
>> + */
>> +#define BUILD_BUG_DECL(name, cond) \
>> + static __initdata struct { \
>> + int BUILD_BUG_DECL_ ## name[1 - 2*!!(cond)]; \
>> + } BUILD_BUG_DECL_ ##name[0] __attribute__((unused))
>> +
>>
>> It lets you check array consistency at compile-time,
>> rather than waiting til run-time.
>
> I don't see how this is an improvement over BUILD_BUG_ON() which
> does the same thing.
>
almost the same thing.
BUILD_BUG_ON() has a do {} while ( at least when __OPTIMIZE__ is
true), so it cant be used at file-scope,
ie outside of function bodies.
> regards,
> dan carpenter
>
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