steakhal added inline comments.
================
Comment at: clang/lib/StaticAnalyzer/Checkers/NullPtrInterferenceChecker.cpp:166
+/// child is a sink node.
+static bool unconditionallyLeadsHere(const ExplodedNode *N) {
+ size_t NonSinkNodeCount = llvm::count_if(
----------------
xazax.hun wrote:
> NoQ wrote:
> > xazax.hun wrote:
> > > Szelethus wrote:
> > > > xazax.hun wrote:
> > > > > xazax.hun wrote:
> > > > > > Consider the following code snippet:
> > > > > > ```
> > > > > > void f(int *p, bool b)
> > > > > > {
> > > > > > if (b) {
> > > > > > *p = 4;
> > > > > > }
> > > > > > if (p) {
> > > > > > ...
> > > > > > }
> > > > > > }
> > > > > > ```
> > > > > >
> > > > > > I suspect that we would get a warning for the code above. I think
> > > > > > warning on the code above might be reasonable (the values of `b`
> > > > > > and `p` might be correlated but in some cases the analyzer has no
> > > > > > way to know this, probably some assertions could make the code
> > > > > > clearer in that case).
> > > > > >
> > > > > > My problem is with the wording of the error message.
> > > > > > The warning `Pointer is unconditionally non-null here` on the null
> > > > > > check is not true for the code above.
> > > > > Also, if the check would warn for the code snippet above, the note
> > > > > "suggest moving the condition here" would also be incorrect.
> > > > What if we demand that the the `CFGBlock` of the dereference must
> > > > dominate the `CFGBlock` of the condition point?
> > > I think it makes sense to warn both when the dereference dominates the
> > > null check, and when the null check post-dominates the dereference. We
> > > just want to give different error messages in those cases.
> > > What if we demand that the the CFGBlock of the dereference must dominate
> > > the CFGBlock of the condition point?
> >
> > ```lang=c
> > *p = 4;
> > if (b) {
> > p = bar();
> > }
> > if (p) {
> > ...
> > }
> > ```
> >
> Yup, this is a nice example. I cannot think of an easy way around this using
> symbolic execution.
Ah, I see. However, empirically, the checker showed really promising results.
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https://reviews.llvm.org/D120992/new/
https://reviews.llvm.org/D120992
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