Quite interesting. Thanks for elaborating.
On Sun, Jul 14, 2013 at 11:56 PM, Kristopher Micinski < [email protected]> wrote: > At the risk of being too tangential... null pointer analysis is a very > popular static analysis. Tons of Java based static analysis engines > implement it using any off the shelf techniques: abstract > interpretation (execute a piece of the program which carries an > abstract value saying "this is null" or "this is not null"), > constraint based analyses (draw a bunch of constraints from the > program text which correspond to how pointers propagate), or some > simpler ad hoc techniques. > > The basic idea is pretty simple: you look at the set of possible > things a reference could point to, and if it's ever possible that > thing can be null, you treat it that way. > > E.g., > > if (..) { > x = thing1 > } > else { > y = null; > } > p = x; > > would mean, if x can be null, then p can be null (so not here, but > would be if the else assigned to x instead). Then you propagate > changes throughout the program, again and again until you cover > everything. Constraint solving does the same thing, but phrased as a > set of constraints which have to be solved. > > Since this is wildly imprecise you need to employ some strategies to > refine it. > > E.g., > > if (some_very_hard_to_solve_arithmetic_formula_that_is_false_here) { > p = null; > } > > Will generally cause static analysis to give the wrong answer (saying > p may be null when in fact it never will be) > > -- > > What this means in the real world is that you can take FindBugs and > run it on your program. Findbugs isn't a complete analysis (it will > sometimes fail to report bugs when they *are* there), but it's very > usable and well tuned for production java code. > > Kris > > On Mon, Jul 15, 2013 at 12:28 AM, TreKing <[email protected]> wrote: > > > > On Sun, Jul 14, 2013 at 10:08 PM, Kristopher Micinski > > <[email protected]> wrote: > >> > >> I think this is probably a valid thing to consider in most APIs, > >> especially if they're statically linked APIs, where you can actually > check. > > > > > > Going off topic a bit, but maybe this will be of interest to the OP as > well, > > given the subject matter. > > > > I'm curious as to how you check a statically linked library for > conditions > > like this. So if I have some statically linked lib "Foo.jar" with some > > method "public void Bar(SomeObject object)", I can do some check to > verify > > that "object" may or may not be null when used in my code? > > > > > > > ------------------------------------------------------------------------------------------------- > > TreKing - Chicago transit tracking app for Android-powered devices > > > > -- > > -- > > You received this message because you are subscribed to the Google > > Groups "Android Developers" group. > > To post to this group, send email to [email protected] > > To unsubscribe from this group, send email to > > [email protected] > > For more options, visit this group at > > http://groups.google.com/group/android-developers?hl=en > > --- > > You received this message because you are subscribed to the Google Groups > > "Android Developers" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [email protected]. > > For more options, visit https://groups.google.com/groups/opt_out. > > > > > > -- > -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Android Developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- ------------------------------------------------------------------------------------------------- TreKing <http://sites.google.com/site/rezmobileapps/treking> - Chicago transit tracking app for Android-powered devices -- -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en --- You received this message because you are subscribed to the Google Groups "Android Developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
