clang-tools-extra/clang-tidy/bugprone/MultiLevelImplicitPointerConversionCheck.cpp

   1 //===--- MultiLevelImplicitPointerConversionCheck.cpp - clang-tidy --------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "MultiLevelImplicitPointerConversionCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/ASTMatchers/ASTMatchFinder.h"
  12
  13 using namespace clang::ast_matchers;
  14
  15 namespace clang::tidy::bugprone {
  16
  17 static unsigned getPointerLevel(const QualType &PtrType) {
  18   if (!PtrType->isPointerType())
  19     return 0U;
  20
  21   return 1U + getPointerLevel(PtrType->castAs<PointerType>()->getPointeeType());
  22 }
  23
  24 namespace {
  25
  26 AST_MATCHER(ImplicitCastExpr, isMultiLevelPointerConversion) {
  27   const QualType TargetType = Node.getType()
  28                                   .getCanonicalType()
  29                                   .getNonReferenceType()
  30                                   .getUnqualifiedType();
  31   const QualType SourceType = Node.getSubExpr()
  32                                   ->getType()
  33                                   .getCanonicalType()
  34                                   .getNonReferenceType()
  35                                   .getUnqualifiedType();
  36
  37   if (TargetType == SourceType)
  38     return false;
  39
  40   const unsigned TargetPtrLevel = getPointerLevel(TargetType);
  41   if (0U == TargetPtrLevel)
  42     return false;
  43
  44   const unsigned SourcePtrLevel = getPointerLevel(SourceType);
  45   if (0U == SourcePtrLevel)
  46     return false;
  47
  48   return SourcePtrLevel != TargetPtrLevel;
  49 }
  50
  51 AST_MATCHER(QualType, isPointerType) {
  52   const QualType Type =
  53       Node.getCanonicalType().getNonReferenceType().getUnqualifiedType();
  54
  55   return !Type.isNull() && Type->isPointerType();
  56 }
  57
  58 } // namespace
  59
  60 void MultiLevelImplicitPointerConversionCheck::registerMatchers(
  61     MatchFinder *Finder) {
  62   Finder->addMatcher(
  63       implicitCastExpr(hasCastKind(CK_BitCast), isMultiLevelPointerConversion(),
  64                        unless(hasParent(explicitCastExpr(
  65                            hasDestinationType(isPointerType())))))
  66           .bind("expr"),
  67       this);
  68 }
  69
  70 std::optional<TraversalKind>
  71 MultiLevelImplicitPointerConversionCheck::getCheckTraversalKind() const {
  72   return TK_AsIs;
  73 }
  74
  75 void MultiLevelImplicitPointerConversionCheck::check(
  76     const MatchFinder::MatchResult &Result) {
  77   const auto *MatchedExpr = Result.Nodes.getNodeAs<ImplicitCastExpr>("expr");
  78   QualType Target = MatchedExpr->getType().getDesugaredType(*Result.Context);
  79   QualType Source =
  80       MatchedExpr->getSubExpr()->getType().getDesugaredType(*Result.Context);
  81
  82   diag(MatchedExpr->getExprLoc(), "multilevel pointer conversion from %0 to "
  83                                   "%1, please use explicit cast")
  84       << Source << Target;
  85 }
  86
  87 } // namespace clang::tidy::bugprone