compilerplugins/clang/cstylecast.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
  10 #include <cassert>
  11 #include <string>
  12 #include "plugin.hxx"
  13 #include "compat.hxx"
  14
  15 //
  16 // We don't like using C-style casts in C++ code
  17 //
  18
  19 namespace {
  20
  21 bool hasCLanguageLinkageType(FunctionDecl const * decl) {
  22     return decl->isExternC() || compat::isInExternCContext(*decl);
  23 }
  24
  25 QualType resolvePointers(QualType type) {
  26     while (type->isPointerType()) {
  27         type = type->getAs<PointerType>()->getPointeeType();
  28     }
  29     return type;
  30 }
  31
  32 class CStyleCast:
  33     public RecursiveASTVisitor<CStyleCast>, public loplugin::Plugin
  34 {
  35 public:
  36     explicit CStyleCast(InstantiationData const & data):
  37         Plugin(data), externCFunction(false)
  38     {}
  39
  40     virtual void run() override {
  41         if (compiler.getLangOpts().CPlusPlus) {
  42             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
  43         }
  44     }
  45
  46     bool TraverseFunctionDecl(FunctionDecl * decl);
  47
  48     bool VisitCStyleCastExpr(const CStyleCastExpr * expr);
  49
  50 private:
  51     bool externCFunction;
  52 };
  53
  54 static const char * recommendedFix(clang::CastKind ck) {
  55     switch(ck) {
  56         case CK_IntegralToPointer: return "reinterpret_cast";
  57         case CK_PointerToIntegral: return "reinterpret_cast";
  58         case CK_BaseToDerived: return "static_cast";
  59         default: return "???";
  60     }
  61 }
  62
  63 bool CStyleCast::TraverseFunctionDecl(FunctionDecl * decl) {
  64     bool ext = hasCLanguageLinkageType(decl)
  65         && decl->isThisDeclarationADefinition();
  66     if (ext) {
  67         assert(!externCFunction);
  68         externCFunction = true;
  69     }
  70     bool ret = RecursiveASTVisitor::TraverseFunctionDecl(decl);
  71     if (ext) {
  72         externCFunction = false;
  73     }
  74     return ret;
  75 }
  76
  77 bool CStyleCast::VisitCStyleCastExpr(const CStyleCastExpr * expr) {
  78     if (ignoreLocation(expr)) {
  79         return true;
  80     }
  81     // casting to void is typically used when a parameter or field is only used in
  82     // debug mode, and we want to eliminate an "unused" warning
  83     if( expr->getCastKind() == CK_ToVoid ) {
  84         return true;
  85     }
  86     // ignore integral-type conversions for now, there is unsufficient agreement about
  87     // the merits of C++ style casting in this case
  88     if( expr->getCastKind() == CK_IntegralCast ) {
  89         return true;
  90     }
  91     if( expr->getCastKind() == CK_NoOp ) {
  92         QualType t1 = expr->getSubExpr()->getType();
  93         QualType t2 = expr->getType();
  94         if (t1->isPointerType() && t2->isPointerType()) {
  95             t1 = t1->getAs<PointerType>()->getPointeeType();
  96             t2 = t2->getAs<PointerType>()->getPointeeType();
  97         } else if (t1->isLValueReferenceType() && t2->isLValueReferenceType()) {
  98             t1 = t1->getAs<LValueReferenceType>()->getPointeeType();
  99             t2 = t2->getAs<LValueReferenceType>()->getPointeeType();
 100         } else {
 101             return true;
 102         }
 103         if (expr->getSubExprAsWritten()->getType() != expr->getType()
 104             && (!t1.isMoreQualifiedThan(t2)
 105                 || (t1.getUnqualifiedType().getCanonicalType().getTypePtr()
 106                     != (t2.getUnqualifiedType().getCanonicalType()
 107                         .getTypePtr()))))
 108         {
 109             return true;
 110         }
 111     }
 112     std::string incompFrom;
 113     std::string incompTo;
 114     if( expr->getCastKind() == CK_BitCast ) {
 115         if (resolvePointers(expr->getSubExprAsWritten()->getType())
 116             ->isIncompleteType())
 117         {
 118             incompFrom = "incomplete ";
 119         }
 120         if (resolvePointers(expr->getType())->isIncompleteType()) {
 121             incompTo = "incomplete ";
 122         }
 123     }
 124     if (externCFunction || expr->getLocStart().isMacroID()) {
 125         SourceLocation spellingLocation = compiler.getSourceManager().getSpellingLoc(
 126             expr->getLocStart());
 127         StringRef filename = compiler.getSourceManager().getFilename(spellingLocation);
 128         // ignore C code
 129         if ( filename.endswith(".h") ) {
 130             return true;
 131         }
 132     }
 133     report(
 134         DiagnosticsEngine::Warning,
 135         "c-style cast, type=%0, from=%1%2, to=%3%4, recommendedFix=%5",
 136         expr->getSourceRange().getBegin())
 137       << expr->getCastKind()
 138       << incompFrom << expr->getSubExprAsWritten()->getType()
 139       << incompTo << expr->getType()
 140       << recommendedFix(expr->getCastKind())
 141       << expr->getSourceRange();
 142     return true;
 143 }
 144
 145 loplugin::Plugin::Registration< CStyleCast > X("cstylecast");
 146
 147 }
 148
 149 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */