On 03/15/2014 12:59 PM, Hans Verkuil wrote:
> Hi!
>
> Here is another sparse error that I get when running sparse over
> drivers/media/v4l2-core/v4l2-ioctl.c:
>
> drivers/media/v4l2-core/v4l2-ioctl.c:2043:9: error: bad integer constant expression
> drivers/media/v4l2-core/v4l2-ioctl.c:2044:9: error: bad integer constant expression
> drivers/media/v4l2-core/v4l2-ioctl.c:2045:9: error: bad integer constant expression
> drivers/media/v4l2-core/v4l2-ioctl.c:2046:9: error: bad integer constant expression
>
> etc.
>
> The root cause of that turns out to be in include/asm-generic/ioctl.h:
>
> #include <uapi/asm-generic/ioctl.h>
>
> /* provoke compile error for invalid uses of size argument */
> extern unsigned int __invalid_size_argument_for_IOC;
> #define _IOC_TYPECHECK(t) \
> ((sizeof(t) == sizeof(t[1]) && \
> sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
> sizeof(t) : __invalid_size_argument_for_IOC)
>
> If it is defined as this:
>
> #define _IOC_TYPECHECK(t) (sizeof(t))
>
> then all is well with the world.
>
> I can patch v4l2-ioctl.c to redefine _IOC_TYPECHECK if __CHECKER__ is defined, but
> shouldn't sparse understand this instead? There was a similar situation with
> ARRAY_SIZE in the past that sparse now understands.
Here is a small test case for this problem:
====== ioc-typecheck.c ======
extern unsigned int __invalid_size_argument_for_IOC;
#define _IOC_TYPECHECK(t) \
((sizeof(t) == sizeof(t[1]) && \
sizeof(t) < (1 << 14)) ? \
sizeof(t) : __invalid_size_argument_for_IOC)
#define TEST_IOCTL (50 | (_IOC_TYPECHECK(unsigned) << 8))
static unsigned iocnrs[] = {
[TEST_IOCTL & 0xff] = 1,
};
/*
* check-name: correct handling of _IOC_TYPECHECK
*
* check-error-start
* check-error-end
*/
====== ioc-typecheck.c ======
Running sparse over this gives:
error: bad integer constant expression
Regards,
Hans
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