On Mon 20-06-16 22:53:26, Dan Carpenter wrote: > On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote: > > On Thu 16-06-16 10:07:09, Dan Carpenter wrote: > > > My static checker complains that this can underflow if arg is negative > > > which is true. > > > > > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > > > > How come? (1 << 30) fits even into 32-bit signed type. So where's the > > problem? > > Bad changelog... I was talking about a different issue. I was casting > it to unsigned to take advantage of type promototion. Assume we have: > > int arg = 1 << 31; > > (arg > (1 << 30)) // <-- this is false > (arg > (1U << 30)) // <-- this is true so there is no underflow. I see, but match_int() - or more precisely match_number() returns -ERANGE when the number is > INT_MAX, subsequently we check whether the number is < 0 (Opt_inode_readahead_blks has flag MOPT_GTE0 set) and bail out if yes. So at the place you are modifying we are sure the number is in [0, INT_MAX]. So the condition (arg > (1 << 30)) is pointless - just defensive programming in case we decide e.g. to upgrade the type of 'arg' to long - but not wrong... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
