[clang-tools-extra] [clang-tidy] Add `bugprone-pointer-arithmetic-on-polymorphic-object` check (PR #91951)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,78 @@
+//===--- PointerArithmeticOnPolymorphicObjectCheck.cpp - clang-tidy--------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "PointerArithmeticOnPolymorphicObjectCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+AST_MATCHER(CXXRecordDecl, isAbstract) { return Node.isAbstract(); }
+} // namespace
+
+PointerArithmeticOnPolymorphicObjectCheck::
+    PointerArithmeticOnPolymorphicObjectCheck(StringRef Name,
+                                              ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      MatchInheritedVirtualFunctions(
+          Options.get("MatchInheritedVirtualFunctions", false)) {}
+
+void PointerArithmeticOnPolymorphicObjectCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "MatchInheritedVirtualFunctions", true);
+}
+
+void PointerArithmeticOnPolymorphicObjectCheck::registerMatchers(
+    MatchFinder *Finder) {
+  const auto PolymorphicPointerExpr =
+      expr(hasType(hasCanonicalType(
+               pointerType(pointee(hasCanonicalType(hasDeclaration(
+                   cxxRecordDecl(unless(isFinal()),
+                                 cxxRecordDecl(hasMethod(isVirtual()))))))))))
+          .bind("pointer");
+
+  const auto PointerExprWithVirtualMethod =
+      expr(hasType(hasCanonicalType(pointerType(
+               pointee(hasCanonicalType(hasDeclaration(cxxRecordDecl(
+                   unless(isFinal()),
+                   anyOf(hasMethod(isVirtualAsWritten()), isAbstract())))))))))
+          .bind("pointer");
+
+  const auto SelectedPointerExpr = MatchInheritedVirtualFunctions
+                                       ? PolymorphicPointerExpr
+                                       : PointerExprWithVirtualMethod;
+
+  const auto ArraySubscript = arraySubscriptExpr(hasBase(SelectedPointerExpr));
+
+  const auto BinaryOperators =
+      binaryOperator(hasAnyOperatorName("+", "-", "+=", "-="),
+                     hasEitherOperand(SelectedPointerExpr));
+
+  const auto UnaryOperators = unaryOperator(
+      hasAnyOperatorName("++", "--"), hasUnaryOperand(SelectedPointerExpr));
+
+  Finder->addMatcher(
+      expr(anyOf(ArraySubscript, BinaryOperators, UnaryOperators)), this);
+}
+
+void PointerArithmeticOnPolymorphicObjectCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *PointerExpr = Result.Nodes.getNodeAs<Expr>("pointer");
+  const CXXRecordDecl *PointeeType =
+      PointerExpr->getType()->getPointeeType()->getAsCXXRecordDecl();
----------------
PiotrZSL wrote:

This may fail with typedefs, you already got cxxRecordDecl in matcher, just bind it to some name, like "Record"

https://github.com/llvm/llvm-project/pull/91951