[PATCH] D51866: [analyzer][UninitializedObjectChecker] New flag to ignore guarded uninitialized fields

[Umann Kristóf via Phabricator via cfe-commits]

Szelethus added inline comments.


================
Comment at: lib/StaticAnalyzer/Checkers/UninitializedObject/UninitializedObjectChecker.cpp:519
+
+    if (FirstAccess->getBeginLoc() < FirstGuard->getBeginLoc())
+      return true;
----------------
george.karpenkov wrote:
> Szelethus wrote:
> > xazax.hun wrote:
> > > I am not sure if this is a reliable way to check if the access is before the guard.
> > > 
> > > Consider:
> > > ```
> > > switch(x): {
> > >    case 2: guard; access; break;
> > >    case 1: access break;
> > > }
> > > ```
> > > 
> > > Here, we have no particular ordering between the access in case 1 and the guard in case 2 at runtime. But relying on the source locations we might come to the false conclusion that there is. Loops, gotos can cause similar problems.
> > > I do understand that this might not be too easy to solve without traversing the cfg and we might not want to do that but I think we should at least add a test/todo. 
> > > I am not sure if this is a reliable way to check if the access is before the guard.
> > I'm 100% sure it isn't. Using the CFG instead of matchers sounds like a great and difficult to implement (at least to me, as I never touched them) idea. It should get rid of the false negatives, at least in part.
> > > [...]  I think we should at least add a test/todo.
> > There are some :)
> > Using the CFG instead of matchers sounds like a great and difficult to implement
> 
> That would also require building a dataflow framework, which we do not have (yet)
Too bad :/ Makes me understand though why it would be valuable to implement it.


https://reviews.llvm.org/D51866