compilerplugins/clang/trivialconstructor.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 <iostream>
  13 #include <unordered_map>
  14 #include <unordered_set>
  15
  16 #include "plugin.hxx"
  17 #include "check.hxx"
  18 #include "config_clang.h"
  19 #include "clang/AST/CXXInheritance.h"
  20 #include "clang/AST/StmtVisitor.h"
  21
  22 // Look for declared constructors that can be trivial (and therefore don't need to be declared)
  23
  24 namespace
  25 {
  26 class TrivialConstructor : public loplugin::FilteringPlugin<TrivialConstructor>
  27 {
  28 public:
  29     explicit TrivialConstructor(loplugin::InstantiationData const& data)
  30         : FilteringPlugin(data)
  31     {
  32     }
  33
  34     virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  35
  36     bool VisitCXXConstructorDecl(CXXConstructorDecl const*);
  37
  38 private:
  39     bool HasTrivialConstructorBody(const CXXRecordDecl* BaseClassDecl,
  40                                    const CXXRecordDecl* MostDerivedClassDecl);
  41     bool FieldHasTrivialConstructorBody(const FieldDecl* Field);
  42 };
  43
  44 bool TrivialConstructor::VisitCXXConstructorDecl(CXXConstructorDecl const* constructorDecl)
  45 {
  46     if (ignoreLocation(constructorDecl))
  47         return true;
  48     if (!constructorDecl->hasTrivialBody())
  49         return true;
  50     if (constructorDecl->isExplicit())
  51         return true;
  52     if (!constructorDecl->isDefaultConstructor())
  53         return true;
  54     if (constructorDecl->getNumParams() != 0)
  55         return true;
  56     if (!constructorDecl->inits().empty())
  57         return true;
  58     if (constructorDecl->getExceptionSpecType() != EST_None)
  59         return true;
  60     if (constructorDecl->getAccess() != AS_public)
  61         return true;
  62     if (!constructorDecl->isThisDeclarationADefinition())
  63         return true;
  64     if (isInUnoIncludeFile(
  65             compiler.getSourceManager().getSpellingLoc(constructorDecl->getLocation())))
  66         return true;
  67     const CXXRecordDecl* recordDecl = constructorDecl->getParent();
  68     if (std::distance(recordDecl->ctor_begin(), recordDecl->ctor_end()) != 1)
  69         return true;
  70     // Constructor templates are not included in ctor_begin()..ctor_end() above, so also do a slow
  71     // check across all decls():
  72     for (auto d : recordDecl->decls())
  73     {
  74         if (auto const d2 = dyn_cast<FunctionTemplateDecl>(d))
  75         {
  76             if (isa<CXXConstructorDecl>(d2->getTemplatedDecl()))
  77             {
  78                 return true;
  79             }
  80         }
  81     }
  82     if (!HasTrivialConstructorBody(recordDecl, recordDecl))
  83         return true;
  84
  85     report(DiagnosticsEngine::Warning, "no need for explicit constructor decl",
  86            constructorDecl->getLocation())
  87         << constructorDecl->getSourceRange();
  88     if (constructorDecl->getCanonicalDecl() != constructorDecl)
  89     {
  90         constructorDecl = constructorDecl->getCanonicalDecl();
  91         report(DiagnosticsEngine::Warning, "no need for explicit constructor decl",
  92                constructorDecl->getLocation())
  93             << constructorDecl->getSourceRange();
  94     }
  95     return true;
  96 }
  97
  98 bool TrivialConstructor::HasTrivialConstructorBody(const CXXRecordDecl* BaseClassDecl,
  99                                                    const CXXRecordDecl* MostDerivedClassDecl)
 100 {
 101     if (BaseClassDecl != MostDerivedClassDecl && !BaseClassDecl->hasTrivialDefaultConstructor())
 102         return false;
 103
 104     // Check fields.
 105     for (const auto* field : BaseClassDecl->fields())
 106         if (!FieldHasTrivialConstructorBody(field))
 107             return false;
 108
 109     // Check non-virtual bases.
 110     for (const auto& I : BaseClassDecl->bases())
 111     {
 112         if (I.isVirtual())
 113             continue;
 114         if (!I.getType()->isRecordType())
 115             continue;
 116         const CXXRecordDecl* NonVirtualBase = I.getType()->getAsCXXRecordDecl();
 117         if (NonVirtualBase && !HasTrivialConstructorBody(NonVirtualBase, MostDerivedClassDecl))
 118             return false;
 119     }
 120
 121     if (BaseClassDecl == MostDerivedClassDecl)
 122     {
 123         // Check virtual bases.
 124         for (const auto& I : BaseClassDecl->vbases())
 125         {
 126             if (!I.getType()->isRecordType())
 127                 continue;
 128             const CXXRecordDecl* VirtualBase = I.getType()->getAsCXXRecordDecl();
 129             if (VirtualBase && !HasTrivialConstructorBody(VirtualBase, MostDerivedClassDecl))
 130                 return false;
 131         }
 132     }
 133     return true;
 134 }
 135
 136 bool TrivialConstructor::FieldHasTrivialConstructorBody(const FieldDecl* Field)
 137 {
 138     QualType FieldBaseElementType = compiler.getASTContext().getBaseElementType(Field->getType());
 139
 140     const RecordType* RT = FieldBaseElementType->getAs<RecordType>();
 141     if (!RT)
 142         return true;
 143
 144     CXXRecordDecl* FieldClassDecl = cast<CXXRecordDecl>(RT->getDecl());
 145
 146     // The constructor for an implicit anonymous union member is never invoked.
 147     if (FieldClassDecl->isUnion() && FieldClassDecl->isAnonymousStructOrUnion())
 148         return false;
 149
 150     return FieldClassDecl->hasTrivialDefaultConstructor();
 151 }
 152
 153 loplugin::Plugin::Registration<TrivialConstructor> X("trivialconstructor", true);
 154 }
 155
 156 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */