compilerplugins/clang/typeidcomparison.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   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
  10 // Find (in-)equality comparisons between typeid expressions that can never succeed.  For now, just
  11 // detects cases where the two involved types are structurally different, one a pointer type and the
  12 // other a non-pointer type.
  13
  14 #ifndef LO_CLANG_SHARED_PLUGINS
  15
  16 #include "plugin.hxx"
  17
  18 namespace
  19 {
  20 class TypeidComparison final : public loplugin::FilteringPlugin<TypeidComparison>
  21 {
  22 public:
  23     explicit TypeidComparison(loplugin::InstantiationData const& data)
  24         : FilteringPlugin(data)
  25     {
  26     }
  27
  28     // For CXXRewrittenBinaryOperator `typeid(...) != typeid(...)`:
  29     bool shouldVisitImplicitCode() const { return true; }
  30
  31     bool preRun() override { return compiler.getLangOpts().CPlusPlus; }
  32
  33     void run() override
  34     {
  35         if (preRun())
  36         {
  37             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
  38         }
  39     }
  40
  41     bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* expr)
  42     {
  43         if (ignoreLocation(expr))
  44         {
  45             return true;
  46         }
  47         auto const op = expr->getOperator();
  48         if (op != OO_EqualEqual && op != OO_ExclaimEqual)
  49         {
  50             return true;
  51         }
  52         assert(expr->getNumArgs() == 2);
  53         auto const e1 = dyn_cast<CXXTypeidExpr>(expr->getArg(0)->IgnoreParenImpCasts());
  54         if (e1 == nullptr)
  55         {
  56             return true;
  57         }
  58         auto const e2 = dyn_cast<CXXTypeidExpr>(expr->getArg(1)->IgnoreParenImpCasts());
  59         if (e2 == nullptr)
  60         {
  61             return true;
  62         }
  63         auto const t1 = getOperandType(e1);
  64         auto const t2 = getOperandType(e2);
  65         if (t1->isPointerType() == t2->isPointerType())
  66         {
  67             return true;
  68         }
  69         report(DiagnosticsEngine::Warning,
  70                "comparison of type info of mixed pointer and non-pointer types %0 and %1 can never "
  71                "succeed",
  72                expr->getExprLoc())
  73             << t1 << t2 << expr->getSourceRange();
  74         return true;
  75     }
  76
  77 private:
  78     QualType getOperandType(CXXTypeidExpr const* expr)
  79     {
  80         return expr->isTypeOperand() ? expr->getTypeOperand(compiler.getASTContext())
  81                                      : expr->getExprOperand()->getType();
  82     }
  83 };
  84
  85 static loplugin::Plugin::Registration<TypeidComparison> typeidcomparison("typeidcomparison");
  86 }
  87
  88 #endif
  89
  90 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */