[clang] [clang][StaticAnalyzer] Reduce MallocSizeofChecker false positives for layout-compatible types (PR #200253)

[Balázs Benics via cfe-commits]

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@@ -149,24 +149,40 @@ static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
     if (A.getTypePtr() == B.getTypePtr())
       return true;
 
+    const PointerType *ptrA = A->getAs<PointerType>();
+    const PointerType *ptrB = B->getAs<PointerType>();
+
     // When neither type is a pointer and exactly one is a record type, check
     // target-specific size and alignment. This avoids false positives for
     // types that wrap another type with the same layout (e.g.
     // std::atomic<int32_t> vs int32_t, or struct{int32_t x;} vs int32_t),
     // while preserving warnings for unrelated types that happen to share a
     // size (e.g. long vs double, struct A vs struct B).
-    if (!A->getAs<PointerType>() && !B->getAs<PointerType>() &&
-        (A->isRecordType() != B->isRecordType()) && !A->isIncompleteType() &&
-        !B->isIncompleteType() && C.getTypeSize(A) == C.getTypeSize(B) &&
-        C.getTypeAlign(A) <= C.getTypeAlign(B))
-      return true;
-
-    if (const PointerType *ptrA = A->getAs<PointerType>())
-      if (const PointerType *ptrB = B->getAs<PointerType>()) {
-        A = ptrA->getPointeeType();
-        B = ptrB->getPointeeType();
-        continue;
+    if (!ptrA && !ptrB && (A->isRecordType() != B->isRecordType()) &&
+        !A->isIncompleteType() && !B->isIncompleteType()) {
+      const RecordType *RecTy = A->getAs<RecordType>();
+      QualType Scalar = B;
+      if (!RecTy) {
+        RecTy = B->getAs<RecordType>();
+        Scalar = A;
       }
+      if (const CXXRecordDecl *RD =
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steakhal wrote:

According to the LLVM style, one does not need to name the type in the declaration if it was already spelled in the initializer expression. You can use `auto` here.

https://github.com/llvm/llvm-project/pull/200253