[clang-tools-extra] [clang-tidy]add new check `bugprone-compare-pointer-to-member-virtual-function` (PR #66055)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,105 @@
+//===--- ComparePointerToMemberVirtualFunctionCheck.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 "ComparePointerToMemberVirtualFunctionCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTTypeTraits.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/OperationKinds.h"
+#include "clang/AST/Type.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/DiagnosticIDs.h"
+#include "llvm/ADT/SmallVector.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+AST_MATCHER(CXXMethodDecl, isVirtual) { return Node.isVirtual(); }
+
+static const char *const ErrorMsg =
+    "A pointer to member virtual function shall only be tested for equality "
+    "with null-pointer-constant.";
+
+} // namespace
+
+void ComparePointerToMemberVirtualFunctionCheck::registerMatchers(
+    MatchFinder *Finder) {
+
+  auto DirectMemberVirtualFunctionPointer = unaryOperator(
+      allOf(hasOperatorName("&"),
+            hasUnaryOperand(declRefExpr(to(cxxMethodDecl(isVirtual()))))));
+  auto IndirectMemberPointer =
+      ignoringImpCasts(declRefExpr().bind("indirect_member_pointer"));
+
+  Finder->addMatcher(
+      binaryOperator(
+          allOf(hasAnyOperatorName("==", "!="),
+                hasEitherOperand(
+                    hasType(memberPointerType(pointee(functionType())))),
+                anyOf(hasEitherOperand(DirectMemberVirtualFunctionPointer),
+                      hasEitherOperand(IndirectMemberPointer)),
+                unless(hasEitherOperand(
+                    castExpr(hasCastKind(CK_NullToMemberPointer))))))
+          .bind("binary_operator"),
+      this);
+}
+
+void ComparePointerToMemberVirtualFunctionCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const BinaryOperator *BO =
+      Result.Nodes.getNodeAs<BinaryOperator>("binary_operator");
+  const DeclRefExpr *DRE =
+      Result.Nodes.getNodeAs<DeclRefExpr>("indirect_member_pointer");
+
+  if (DRE == nullptr) {
+    // compare with pointer to member virtual function.
+    diag(BO->getOperatorLoc(), ErrorMsg);
+    return;
+  }
+  // compare with variable which type is pointer to member function.
+  llvm::SmallVector<SourceLocation, 12U> SameSignatureVirtualMethods{};
+  const auto *MPT = cast<MemberPointerType>(DRE->getType().getCanonicalType());
+  const Type *T = MPT->getClass();
+  if (T == nullptr)
+    return;
+  const CXXRecordDecl *RD = T->getAsCXXRecordDecl();
+  if (RD == nullptr)
+    return;
+
+  const bool StopVisit = false;
+
+  auto VisitSameSignatureVirtualMethods =
+      [&](const CXXRecordDecl *CurrentRecordDecl) -> bool {
+    bool Ret = !StopVisit;
+    for (const auto *MD : CurrentRecordDecl->methods()) {
+      if (MD->isVirtual() && MD->getType() == MPT->getPointeeType()) {
+        SameSignatureVirtualMethods.push_back(MD->getBeginLoc());
+        Ret = StopVisit;
+      }
+    }
+    return Ret;
+  };
+
+  if (StopVisit != VisitSameSignatureVirtualMethods(RD)) {
+    RD->forallBases(VisitSameSignatureVirtualMethods);
+  }
+
+  if (!SameSignatureVirtualMethods.empty()) {
+    diag(BO->getOperatorLoc(), ErrorMsg);
+    for (const auto Loc : SameSignatureVirtualMethods)
+      diag(Loc, "potential member virtual function.", DiagnosticIDs::Note);
----------------
PiotrZSL wrote:

maybe "potential member virtual function is declared here."

https://github.com/llvm/llvm-project/pull/66055