[clang] [LifetimeSafety] Track origins through array subscript and array-to-pointer decay (PR #186902)

[Utkarsh Saxena via cfe-commits]

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@@ -470,6 +474,16 @@ void FactsGenerator::VisitLambdaExpr(const LambdaExpr *LE) {
   }
 }
 
+void FactsGenerator::VisitArraySubscriptExpr(const ArraySubscriptExpr *ASE) {
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usx95 wrote:

Can you please verify that these do not fire in practice. Maybe try to build LLVM using your head Clang and see if it fires.

I use the following cmake in a separate build directory:

```
cmake -G Ninja path/to/llvm-project/llvm  \               
  -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;" \         -DLLVM_ENABLE_ASSERTIONS=On  \                        
  -DCMAKE_C_FLAGS_RELEASE="-O3 -gmlt -UNDEBUG" \  
  -DCMAKE_CXX_FLAGS_RELEASE="-O3 -gmlt -UNDEBUG -Wlifetime-safety" \
  -DCMAKE_C_COMPILER="/path/to/build/bin/clang" \
  -DCMAKE_CXX_COMPILER="/path/to/build/bin/clang++" \
  -DLLVM_USE_LINKER=lld -DLLVM_CCACHE_BUILD=1
```

`-Wlifetime-safety` might be noisy. You can try `-Wlifetime-safety-permissive` instead.

https://github.com/llvm/llvm-project/pull/186902