[clang] [clang] Check null TypeSourceInfo in CreateUnaryExprOrTypeTraitExpr (PR #112111)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Andrew Sukach (sookach)

<details>
<summary>Changes</summary>

Fixes #<!-- -->111594. The crash is caused by the following call
https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/ComputeDependence.cpp#L81-L82

We already check for a null TypeInfo when creating a UnaryExprOrTypeTraitExpr here
https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaExpr.cpp#L4616-L4617

but the following lines can, and in the case of the code in the issue, nullify the TypeInfo
https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaExpr.cpp#L4616-L4617

Thus, adding the additional check for nullptr prevents the erroneous memory access.

@<!-- -->shafik Thoughts? Thanks


---
Full diff: https://github.com/llvm/llvm-project/pull/112111.diff


1 Files Affected:

- (modified) clang/lib/Sema/SemaExpr.cpp (+3) 


``````````diff
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 4e37385710af5e..b0bd216c5dc101 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4629,6 +4629,9 @@ ExprResult Sema::CreateUnaryExprOrTypeTraitExpr(TypeSourceInfo *TInfo,
       TInfo->getType()->isVariablyModifiedType())
     TInfo = TransformToPotentiallyEvaluated(TInfo);
 
+  if (!TInfo)
+    return ExprError();
+
   // C99 6.5.3.4p4: the type (an unsigned integer type) is size_t.
   return new (Context) UnaryExprOrTypeTraitExpr(
       ExprKind, TInfo, Context.getSizeType(), OpLoc, R.getEnd());

``````````

</details>


https://github.com/llvm/llvm-project/pull/112111