Messages in this thread | | | Date | Wed, 24 Nov 2004 00:09:59 +0100 (CET) | From | Jesper Juhl <> | Subject | Re: [PATCH] Remove pointless <0 comparison for unsigned variable in fs/fcntl.c |
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On Tue, 23 Nov 2004, Timur Tabi wrote:
> Linus Torvalds wrote: > > > which might warn on an architecture where "pid_t" is just sixteen bits wide. > > Does that make the code wrong? Hell no. > > Wouldn't something like "sizeof(pid_t) > 2" be a better test? It certainly > would be a lot easier to understand than comparing with 0xffff. > That was not the point of the example Linus gave. The example Linus gave was a function taking a pid_t argument and then comparing the value of the argument passed against 0xffff - the /value/ of the pid_t argument passed, not the size of the datatype.
int fn(pid_t a) { if (a > 0xffff) ... }
if pid_t is 16 bit, then the value can never be greater than 0xffff but, if pid_t is greater than 16 bit, say 32 bit, then the argument "a" could very well contain a value greater than 0xffff and then the comparison makes perfect sense. So, while you'd get a warning on architectures where pid_t is 16bit or less you won't get a warning when pid_t is greater than 16 bit. "fixing" that warning would clearly be wrong, no argument about that.
-- Jesper Juhl
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