[clang] [Clang] Prevent potential null pointer dereferences (PR #117176)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-hlsl

Author: None (smanna12)

<details>
<summary>Changes</summary>

This commit addresses several null pointer issues identified by static analysis by replacing dyn_cast<> with cast<> and getAs<> with castAs<> in various parts of the Clang codebase. The cast and castAs method is used to ensure that the type is correctly cast, which helps prevent potential null pointer dereferences.

Changes:
1. ASTContext.cpp:
   Replaced dyn_cast with cast to ensure that the type is correctly cast to AttributedType.

2. SemaFunctionEffects.cpp:
 Replaced getAs with castAs to ensure that the type is correctly cast to FunctionProtoType.

3. SemaHLSL.cpp:
  Replaced getAs with castAs to ensure that the type is correctly cast to VectorType.

---
Full diff: https://github.com/llvm/llvm-project/pull/117176.diff


3 Files Affected:

- (modified) clang/lib/AST/ASTContext.cpp (+1-1) 
- (modified) clang/lib/Sema/SemaFunctionEffects.cpp (+1-1) 
- (modified) clang/lib/Sema/SemaHLSL.cpp (+2-2) 


``````````diff
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 14fbadbc35ae5d..23df7878a3bf29 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -3558,7 +3558,7 @@ ASTContext::adjustType(QualType Orig,
                        llvm::function_ref<QualType(QualType)> Adjust) const {
   switch (Orig->getTypeClass()) {
   case Type::Attributed: {
-    const auto *AT = dyn_cast<AttributedType>(Orig);
+    const auto *AT = cast<AttributedType>(Orig);
     return getAttributedType(AT->getAttrKind(),
                              adjustType(AT->getModifiedType(), Adjust),
                              adjustType(AT->getEquivalentType(), Adjust),
diff --git a/clang/lib/Sema/SemaFunctionEffects.cpp b/clang/lib/Sema/SemaFunctionEffects.cpp
index 6fe4d2353a2282..c5c1e3fb41a2ff 100644
--- a/clang/lib/Sema/SemaFunctionEffects.cpp
+++ b/clang/lib/Sema/SemaFunctionEffects.cpp
@@ -627,7 +627,7 @@ class Analyzer {
           IsNoexcept = isNoexcept(FD);
         } else if (auto *BD = dyn_cast<BlockDecl>(D)) {
           if (auto *TSI = BD->getSignatureAsWritten()) {
-            auto *FPT = TSI->getType()->getAs<FunctionProtoType>();
+            auto *FPT = TSI->getType()->castAs<FunctionProtoType>();
             IsNoexcept = FPT->isNothrow() || BD->hasAttr<NoThrowAttr>();
           }
         }
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index f4fc0f2ddc27a6..a1adc66ddb9ce9 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -1908,9 +1908,9 @@ bool SemaHLSL::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
       return true;
     // ensure both args have 3 elements
     int NumElementsArg1 =
-        TheCall->getArg(0)->getType()->getAs<VectorType>()->getNumElements();
+        TheCall->getArg(0)->getType()->casAs<VectorType>()->getNumElements();
     int NumElementsArg2 =
-        TheCall->getArg(1)->getType()->getAs<VectorType>()->getNumElements();
+        TheCall->getArg(1)->getType()->castAs<VectorType>()->getNumElements();
 
     if (NumElementsArg1 != 3) {
       int LessOrMore = NumElementsArg1 > 3 ? 1 : 0;

``````````

</details>


https://github.com/llvm/llvm-project/pull/117176