Monday, September 03, 2001, 11:35:52 PM, David desJardins
<david@desjardins.org> wrote:
Dd> The explicit typing of MIN and MAX will avoid some bugs that have to do
Dd> with the comparison of entities of different types. The explicit typing
Dd> will also introduce some bugs, when a user uses the wrong type (e.g.,
Dd> when the code is initially written with the correct type, but then
Dd> someone later changes the type of the variables, and doesn't remember to
Dd> change the type in the macro call). Overall, I think it will be about a
Dd> wash.
...
Dd> I think the best approach to bug avoidance would be two-argument MIN and
Dd> MAX functions which require that both arguments have the same type, but
Dd> where that can be any type. Then users who want to compare objects of
Dd> different types would have to explicitly cast one to the type of the
Dd> other (or both to a third common type). In the most common case where
Dd> users are simply comparing objects of the same type, there would be no
Dd> need or reason to change the code.
This sounds right!
#define min2(a,b) ... <-- checks for a,b being the same type
#define min3(type,a,b) ... <-- casts a,b to type first
min3(long long,a,b) will be a favorite in bug chasing :-)
Dd> It's simple enough for an external checker to confirm that this rule is
Dd> followed. The same checker could enforce the same rule for "<" and
Dd> other comparison operators, which would probably help eliminate several
Dd> bugs (without the unacceptably clunky LESSTHAN macro).
Good candidate for Stanford checker, but there will be lots of false
positives.
-- Best regards, VDA mailto:VDA@port.imtp.ilyichevsk.odessa.ua http://port.imtp.ilyichevsk.odessa.ua/vda/- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Sep 07 2001 - 21:00:23 EST