The `warn_unused_result' attribute causes a warning to be emitted if a caller of the function with this attribute does not use its return value. This is useful for functions where not checking the result is either a security problem or always a bug, such as `realloc'.
int fn () __attribute__ ((warn_unused_result));
int foo ()
{
if (fn () < 0) return -1;
fn ();
return 0;
}
results in warning on line 5.
On 3/15/07, Prasad Joshi <prasadjoshi124@xxxxxxxxx> wrote:
Hi Dinesh,Some functions in the linux kernel are marked with must_check attribute. For eg. copy_to/from_user () is declared something like this.__must_check attribute indicates for functions for which checking the return value is mantadory.This must have been the case with the function class_device_create_file().
Thanks and Regards,Prasad.
On 3/15/07, Mike Frysinger <vapier.adi@xxxxxxxxx> wrote:On 3/14/07, Dinesh <dbhat@xxxxxxxxx> wrote:
> When I compile our drivers on 2.6.19, I get the following warning message.
>
> warning: ignoring return value of 'class_device_create_file', declared
> with attribute warn_unused_result
>
> The driver does not print any warnings on 2.6.17 and it appears that
> this is related to some sysfs entries.
that's because 2.6.19 was improved to print warnings when people write
code that fail to properly check the results of functions
> Can anyone please tell me how to get rid of these messages?
going out on a limb here, but dont ignore the result of the function
(aka, the result of the function is unused)
incorrect:
class_device_create_file(...);
correct:
result = class_device_create_file(...);
if (result) ...
-mike
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