[clang] [Clang] Prevent null dereferences (PR #115502)

[via cfe-commits]

https://github.com/smanna12 created https://github.com/llvm/llvm-project/pull/115502

This commit addresses several Static Analyzer issues related to potential null dereference by replacing dyn_cast<> with cast<> and getAs<> with castAs<> in various parts of the codes. 

The cast function asserts that the cast is valid, ensuring that the pointer is not null and preventing null dereference errors. 

The changes are made in the following files:
CGBuiltin.cpp: Ensure vector types have exactly 3 elements.
CGExpr.cpp: Ensure member declarations are field declarations.
AnalysisBasedWarnings.cpp: Ensure operations are member expressions.
SemaExprMember.cpp: Ensure base types are extended vector types.

These changes ensure that the types are correctly cast and prevent potential null dereference issues, improving the robustness and safety of the code.

>From d922aea02da8ddb0fe27ed21e1fe94bcb7e5d061 Mon Sep 17 00:00:00 2001
From: "Manna, Soumi" <soumi.manna at intel.com>
Date: Fri, 8 Nov 2024 07:40:37 -0800
Subject: [PATCH] [Clang] Prevent null dereference

---
 clang/lib/CodeGen/CGBuiltin.cpp          | 4 ++--
 clang/lib/CodeGen/CGExpr.cpp             | 2 +-
 clang/lib/Sema/AnalysisBasedWarnings.cpp | 2 +-
 clang/lib/Sema/SemaExprMember.cpp        | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 430ac5626f89d7..3d494cccf086cd 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -18862,8 +18862,8 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
            "cross operands must have a float representation");
     // make sure each vector has exactly 3 elements
     assert(
-        E->getArg(0)->getType()->getAs<VectorType>()->getNumElements() == 3 &&
-        E->getArg(1)->getType()->getAs<VectorType>()->getNumElements() == 3 &&
+        E->getArg(0)->getType()->castAs<VectorType>()->getNumElements() == 3 &&
+        E->getArg(1)->getType()->castAs<VectorType>()->getNumElements() == 3 &&
         "input vectors must have 3 elements each");
     return Builder.CreateIntrinsic(
         /*ReturnType=*/Op0->getType(), CGM.getHLSLRuntime().getCrossIntrinsic(),
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 096f4c4f550435..0a9ce72fac7d6c 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4374,7 +4374,7 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
           ME &&
           ME->isFlexibleArrayMemberLike(getContext(), StrictFlexArraysLevel) &&
           ME->getMemberDecl()->getType()->isCountAttributedType()) {
-        const FieldDecl *FAMDecl = dyn_cast<FieldDecl>(ME->getMemberDecl());
+        const FieldDecl *FAMDecl = cast<FieldDecl>(ME->getMemberDecl());
         if (const FieldDecl *CountFD = FAMDecl->findCountedByField()) {
           if (std::optional<int64_t> Diff =
                   getOffsetDifferenceInBits(*this, CountFD, FAMDecl)) {
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index c76733e9a774b6..ca487c73b0d909 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -2265,7 +2265,7 @@ class UnsafeBufferUsageReporter : public UnsafeBufferUsageHandler {
       } else if (isa<MemberExpr>(Operation)) {
         // note_unsafe_buffer_operation doesn't have this mode yet.
         assert(!IsRelatedToDecl && "Not implemented yet!");
-        auto ME = dyn_cast<MemberExpr>(Operation);
+        auto ME = cast<MemberExpr>(Operation);
         D = ME->getMemberDecl();
         MsgParam = 5;
       } else if (const auto *ECE = dyn_cast<ExplicitCastExpr>(Operation)) {
diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp
index f1ba26f38520a9..19af3c23095f96 100644
--- a/clang/lib/Sema/SemaExprMember.cpp
+++ b/clang/lib/Sema/SemaExprMember.cpp
@@ -379,7 +379,7 @@ CheckExtVectorComponent(Sema &S, QualType baseType, ExprValueKind &VK,
   //
   // FIXME: This logic can be greatly simplified by splitting it along
   // halving/not halving and reworking the component checking.
-  const ExtVectorType *vecType = baseType->getAs<ExtVectorType>();
+  const ExtVectorType *vecType = baseType->castAs<ExtVectorType>();
 
   // The vector accessor can't exceed the number of elements.
   const char *compStr = CompName->getNameStart();