compilerplugins/clang/unreffun.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 #ifndef LO_CLANG_SHARED_PLUGINS
  11
  12 #include <cassert>
  13 #include <stack>
  14 #include <string>
  15
  16 #include "clang/AST/Attr.h"
  17 #include "clang/Sema/SemaInternal.h" // warn_unused_function
  18
  19 #include "compat.hxx"
  20 #include "plugin.hxx"
  21
  22 namespace {
  23
  24 bool isFriendDecl(Decl const * decl) {
  25     return decl->getFriendObjectKind() != Decl::FOK_None;
  26 }
  27
  28 Decl const * getPreviousNonFriendDecl(Decl const * decl) {
  29     for (;;) {
  30         decl = decl->getPreviousDecl();
  31         if (decl == nullptr || !isFriendDecl(decl)) {
  32             return decl;
  33         }
  34     }
  35 }
  36
  37 bool isSpecialMemberFunction(FunctionDecl const * decl) {
  38     if (auto const ctor = dyn_cast<CXXConstructorDecl>(decl)) {
  39         return ctor->isDefaultConstructor() || ctor->isCopyOrMoveConstructor();
  40     }
  41     if (isa<CXXDestructorDecl>(decl)) {
  42         return true;
  43     }
  44     if (auto const meth = dyn_cast<CXXMethodDecl>(decl)) {
  45         return meth->isCopyAssignmentOperator() || meth->isMoveAssignmentOperator();
  46     }
  47     return false;
  48 }
  49
  50 class UnrefFun: public loplugin::FilteringPlugin<UnrefFun> {
  51 public:
  52     explicit UnrefFun(loplugin::InstantiationData const & data): FilteringPlugin(data) {}
  53
  54     void run() override
  55     { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  56
  57     bool PreTraverseFriendDecl(FriendDecl * decl) {
  58         friendFunction.push( dyn_cast_or_null<FunctionDecl>(decl->getFriendDecl()));
  59         return true;
  60     }
  61     bool PostTraverseFriendDecl(FriendDecl *, bool ) {
  62         friendFunction.pop();
  63         return true;
  64     }
  65     bool TraverseFriendDecl(FriendDecl * decl) {
  66         PreTraverseFriendDecl(decl);
  67         auto const ret = RecursiveASTVisitor::TraverseFriendDecl(decl);
  68         PostTraverseFriendDecl(decl, ret);
  69         return ret;
  70     }
  71
  72     bool VisitFunctionDecl(FunctionDecl const * decl);
  73
  74 private:
  75     std::stack<FunctionDecl const *> friendFunction;
  76 };
  77
  78 bool UnrefFun::VisitFunctionDecl(FunctionDecl const * decl) {
  79     if (ignoreLocation(decl)) {
  80         return true;
  81     }
  82
  83     //TODO, filtering out any functions relating to (class) templates for now:
  84     CXXRecordDecl const * r = dyn_cast<CXXRecordDecl>(decl->getDeclContext());
  85     if (r != nullptr
  86         && (r->getTemplateSpecializationKind() != TSK_Undeclared
  87             || r->isDependentContext()))
  88     {
  89         return true;
  90     }
  91     if (!friendFunction.empty() && decl == friendFunction.top()) {
  92         if (auto const lex = dyn_cast<CXXRecordDecl>(decl->getLexicalDeclContext())) {
  93             if (lex->isDependentContext()) {
  94                 return true;
  95             }
  96         }
  97     }
  98
  99     if (!(decl->isThisDeclarationADefinition() || isFriendDecl(decl)
 100           || decl->isFunctionTemplateSpecialization()))
 101     {
 102         Decl const * prev = getPreviousNonFriendDecl(decl);
 103         if (prev != nullptr/* && prev != decl->getPrimaryTemplate()*/) {
 104             // Workaround for redeclarations that introduce visibility attributes
 105             // (as is done with
 106             //
 107             //  SAL_DLLPUBLIC_EXPORT GType lok_doc_view_get_type();
 108             //
 109             // in libreofficekit/source/gtk/lokdocview.cxx):
 110             if (decl->getAttr<VisibilityAttr>() != nullptr
 111                 && prev->getAttr<VisibilityAttr>() == nullptr)
 112             {
 113                 return true;
 114             }
 115             report(
 116                 DiagnosticsEngine::Warning,
 117                 "redundant function%0 redeclaration", decl->getLocation())
 118                 << ((decl->getTemplatedKind()
 119                      == FunctionDecl::TK_FunctionTemplate)
 120                     ? " template" : "")
 121                 << decl->getSourceRange();
 122             report(
 123                 DiagnosticsEngine::Note, "previous declaration is here",
 124                 prev->getLocation())
 125                 << prev->getSourceRange();
 126             return true;
 127         }
 128     }
 129
 130     FunctionDecl const * canon = decl->getCanonicalDecl();
 131         //TODO: is that the first?
 132     if (canon->isDeleted() || canon->isReferenced()
 133         || !(canon->isDefined()
 134              ? decl->isThisDeclarationADefinition() : decl->isFirstDecl())
 135         || !compiler.getSourceManager().isInMainFile(canon->getLocation())
 136         || isInUnoIncludeFile(canon)
 137         || canon->isMain() || canon->isMSVCRTEntryPoint()
 138         || (decl->getTemplatedKind() == FunctionDecl::TK_FunctionTemplate
 139             && (decl->getDescribedFunctionTemplate()->spec_begin()
 140                 != decl->getDescribedFunctionTemplate()->spec_end()))
 141         || (compiler.getDiagnostics().getDiagnosticLevel(
 142                 diag::warn_unused_function, decl->getLocation())
 143             < DiagnosticsEngine::Warning))
 144     {
 145         return true;
 146     }
 147     if (canon->isExplicitlyDefaulted() && isSpecialMemberFunction(canon)) {
 148         // If a special member function is explicitly defaulted on the first declaration, assume
 149         // that its presence is always due to some interface design consideration, not to explicitly
 150         // request a definition that might be worth to flag as unused (and C++20 may extend
 151         // defaultability beyond special member functions to comparison operators, therefore
 152         // explicitly check here for special member functions only):
 153         return true;
 154     }
 155     LinkageInfo info(canon->getLinkageAndVisibility());
 156     if (info.getLinkage() == compat::Linkage::External
 157         && loplugin::hasCLanguageLinkageType(canon) && canon->isDefined()
 158         && ((decl == canon && info.getVisibility() == DefaultVisibility)
 159             || ((canon->hasAttr<ConstructorAttr>()
 160                  || canon->hasAttr<DestructorAttr>())
 161                 && info.getVisibility() == HiddenVisibility)))
 162     {
 163         return true;
 164     }
 165     auto loc = decl->getLocation();
 166     if (compiler.getSourceManager().isMacroBodyExpansion(loc)
 167         && (Lexer::getImmediateMacroName(
 168                 loc, compiler.getSourceManager(), compiler.getLangOpts())
 169             == "MDDS_MTV_DEFINE_ELEMENT_CALLBACKS"))
 170     {
 171         return true;
 172     }
 173     report(
 174         DiagnosticsEngine::Warning,
 175         (canon->isDefined()
 176          ? (canon->isExternallyVisible()
 177             ? "Unreferenced externally visible function%0 definition"
 178             : "Unreferenced externally invisible function%0 definition")
 179          : "Unreferenced function%0 declaration"),
 180         decl->getLocation())
 181         << (decl->getTemplatedKind() == FunctionDecl::TK_FunctionTemplate
 182             ? " template" : "")
 183         << decl->getSourceRange();
 184     if (canon->isDefined() && !decl->isFirstDecl()) {
 185         report(
 186             DiagnosticsEngine::Note, "first declaration is here",
 187             canon->getLocation())
 188             << canon->getSourceRange();
 189     }
 190     return true;
 191 }
 192
 193 loplugin::Plugin::Registration<UnrefFun> unreffun("unreffun");
 194
 195 }
 196
 197 #endif // LO_CLANG_SHARED_PLUGINS
 198
 199 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */