compilerplugins/clang/faileddyncast.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9 #ifndef LO_CLANG_SHARED_PLUGINS
  10
  11 #include <algorithm>
  12
  13 #include "clang/AST/Attr.h"
  14 #include "clang/AST/CXXInheritance.h"
  15
  16 #include "plugin.hxx"
  17
  18 namespace {
  19
  20 // cf. Clang's clang::AST::CXXDynamicCastExpr::isAlwaysNull
  21 // (lib/AST/ExprCXX.cpp):
  22 bool isAlwaysNull(CXXDynamicCastExpr const * expr) {
  23   QualType SrcType = expr->getSubExpr()->getType();
  24   QualType DestType = expr->getType();
  25
  26   if (const clang::PointerType *SrcPTy = SrcType->getAs<clang::PointerType>()) {
  27     SrcType = SrcPTy->getPointeeType();
  28 #if 0
  29     DestType = DestType->castAs<PointerType>()->getPointeeType();
  30 #else
  31     auto DstPTy = DestType->getAs<clang::PointerType>();
  32     if (!DstPTy)
  33       return false;
  34     DestType = DstPTy->getPointeeType();
  35 #endif
  36   }
  37
  38   if (DestType->isVoidType())
  39     return false;
  40
  41 #if 0
  42   const CXXRecordDecl *SrcRD =
  43     cast<CXXRecordDecl>(SrcType->castAs<RecordType>()->getDecl());
  44 #else
  45   auto SrcRT = SrcType->getAs<RecordType>();
  46   if (!SrcRT)
  47     return false;
  48   const CXXRecordDecl *SrcRD = cast<CXXRecordDecl>(SrcRT->getDecl());
  49 #endif
  50
  51 #if 0
  52   if (!SrcRD->hasAttr<FinalAttr>())
  53     return false;
  54 #endif
  55
  56 #if 0
  57   const CXXRecordDecl *DestRD =
  58     cast<CXXRecordDecl>(DestType->castAs<RecordType>()->getDecl());
  59 #else
  60   auto DestRT = DestType->getAs<RecordType>();
  61   if (!DestRT)
  62     return false;
  63   const CXXRecordDecl *DestRD = cast<CXXRecordDecl>(DestRT->getDecl());
  64 #endif
  65
  66 #if 1
  67   if (!(SrcRD && DestRD))
  68     return false;
  69
  70   if (DestRD->hasAttr<FinalAttr>()) {
  71     CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true,
  72                        /*DetectVirtual=*/false);
  73     if (DestRD->isDerivedFrom(SrcRD, Paths) &&
  74         std::all_of(Paths.begin(), Paths.end(),
  75                     [](CXXBasePath const & Path) {
  76                         return Path.Access != AS_public; }))
  77       return true;
  78   }
  79
  80   if (!SrcRD->hasAttr<FinalAttr>())
  81     return false;
  82 #endif
  83
  84 #if 0
  85   return !DestRD->isDerivedFrom(SrcRD);
  86 #else
  87   return !(DestRD->isDerivedFrom(SrcRD)
  88            || SrcRD->isDerivedFrom(DestRD)
  89            || SrcRD == DestRD);
  90 #endif
  91 }
  92
  93 class FailedDynCast:
  94     public loplugin::FilteringPlugin<FailedDynCast>
  95 {
  96 public:
  97     explicit FailedDynCast(loplugin::InstantiationData const & data):
  98         FilteringPlugin(data) {}
  99
 100     bool shouldVisitTemplateInstantiations() const { return true; }
 101
 102     bool preRun() override;
 103     void run() override;
 104
 105     bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr);
 106 };
 107
 108 bool FailedDynCast::preRun() {
 109     return compiler.getLangOpts().CPlusPlus;
 110 }
 111
 112 void FailedDynCast::run() {
 113     if (preRun()) {
 114         TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
 115     }
 116 }
 117
 118 bool FailedDynCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
 119     if (ignoreLocation(expr)) {
 120         return true;
 121     }
 122     if (isAlwaysNull(expr)) {
 123         report(
 124             DiagnosticsEngine::Warning,
 125             "dynamic_cast from %0 to %1 always fails", expr->getBeginLoc())
 126             << expr->getSubExpr()->getType() << expr->getType()
 127             << expr->getSourceRange();
 128     }
 129     return true;
 130 }
 131
 132 loplugin::Plugin::Registration<FailedDynCast> faileddyncast("faileddyncast");
 133
 134 } // namespace
 135
 136 #endif // LO_CLANG_SHARED_PLUGINS
 137
 138 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */