[clang] [analyzer] Only report the first dereference of the same variable in DanglingPtrDeref (PR #215409)

[Benedek Kaibas via cfe-commits]

================
@@ -181,6 +190,11 @@ void LifetimeModeling::checkDeadSymbols(SymbolReaper &SymReaper,
     if (!SymReaper.isLiveRegion(Region))
       State = State->remove<DeallocatedSourceSet>(Region);
   }
+
+  for (const MemRegion *Region : Reported) {
+    if (!SymReaper.isLiveRegion(Region))
+      State = State->remove<ReportedDeadRegions>(Region);
+  }
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benedekaibas wrote:

I think, yes we should. Currently if there are multiple dereferences the checker emits warning for the first one which makes sense, but what if the user want to check if there are multiple dereferences of the same object afterwards? I think this is where `printState` can "shine" and help the user figure out if there are any more dereferences of the same object.

Applied changes here: [a44befc](https://github.com/llvm/llvm-project/pull/215409/commits/a44befc77019d7a6fa68bd071a0a9e0deb05d70d)

https://github.com/llvm/llvm-project/pull/215409