xazax.hun 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(
----------------
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.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D120992/new/
https://reviews.llvm.org/D120992
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
