On Thu, Jun 12, 2014 at 12:24:25AM +0300, Dan Carpenter wrote:
> Let's forward this to the Sparse mailing list.
>
> We're seeing a Sparse false positive testing
> drivers/staging/comedi/drivers/ni_pcimio.c.
>
> CHECK drivers/staging/comedi/drivers/ni_pcimio.c
> drivers/staging/comedi/drivers/ni_stc.h:720:26: warning: shift too big
> (4294967295) for type int
> drivers/staging/comedi/drivers/ni_stc.h:720:26: warning: shift too big
> (4294967295) for type int
> drivers/staging/comedi/drivers/ni_stc.h:720:26: warning: shift too big
> (4294967295) for type int
> drivers/staging/comedi/drivers/ni_stc.h:720:26: warning: shift too big
> (4294967295) for type int
>
> I have created some test code to demonstrate the problem (attached).
>
> The check_shift_count() warning is only supposed to be printed for
> number literals but because of the way inline functions are expanded it
> still complains even though channel is a variable.
Thanks for the test case; this definitely makes no sense. I don't think
Sparse will suddenly develop enough range analysis or reachability
analysis to handle this case; I think the right answer is to avoid
giving such warnings for shifts with a non-constant RHS.
> #include <stdio.h>
> #include <limits.h>
> #include <string.h>
>
> static inline unsigned ni_stc_dma_channel_select_bitfield(unsigned channel)
> {
> if (channel < 4)
> return 1 << channel;
> return 0;
> }
>
> static inline void filter(int channel)
> {
> if (channel < 0)
> return;
> ni_stc_dma_channel_select_bitfield(channel);
> }
>
> int main(void)
> {
> filter(-1);
>
> return 0;
> }
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