compilerplugins/clang/unnecessaryoverride.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 <string>
  14 #include <iostream>
  15 #include <fstream>
  16 #include <set>
  17
  18 #include <clang/AST/CXXInheritance.h>
  19 #include "plugin.hxx"
  20
  21 /**
  22 look for methods where all they do is call their superclass method
  23 */
  24
  25 namespace {
  26
  27 bool hasMultipleBaseInstances_(
  28     CXXRecordDecl const * derived, CXXRecordDecl const * canonicBase,
  29     bool & hasAsNonVirtualBase, bool & hasAsVirtualBase)
  30 {
  31     for (auto i = derived->bases_begin(); i != derived->bases_end(); ++i) {
  32         auto const cls = i->getType()->getAsCXXRecordDecl();
  33         if (cls == nullptr) {
  34             assert(i->getType()->isDependentType());
  35             // Conservatively assume "yes" for dependent bases:
  36             return true;
  37         }
  38         if (cls->getCanonicalDecl() == canonicBase) {
  39             if (i->isVirtual()) {
  40                 if (hasAsNonVirtualBase) {
  41                     return true;
  42                 }
  43                 hasAsVirtualBase = true;
  44             } else {
  45                 if (hasAsNonVirtualBase || hasAsVirtualBase) {
  46                     return true;
  47                 }
  48                 hasAsNonVirtualBase = true;
  49             }
  50         } else if (hasMultipleBaseInstances_(
  51                        cls, canonicBase, hasAsNonVirtualBase, hasAsVirtualBase))
  52         {
  53             return true;
  54         }
  55     }
  56     return false;
  57 }
  58
  59 bool hasMultipleBaseInstances(
  60     CXXRecordDecl const * derived, CXXRecordDecl const * base)
  61 {
  62     bool nonVirt = false;
  63     bool virt = false;
  64     return hasMultipleBaseInstances_(
  65         derived, base->getCanonicalDecl(), nonVirt, virt);
  66 }
  67
  68 class UnnecessaryOverride:
  69     public loplugin::FilteringPlugin<UnnecessaryOverride>
  70 {
  71 public:
  72     explicit UnnecessaryOverride(loplugin::InstantiationData const & data): FilteringPlugin(data) {}
  73
  74     virtual bool preRun() override
  75     {
  76         // ignore some files with problematic macros
  77         StringRef fn(handler.getMainFileName());
  78         if (loplugin::isSamePathname(fn, SRCDIR "/sd/source/ui/framework/factories/ChildWindowPane.cxx"))
  79             return false;
  80         if (loplugin::isSamePathname(fn, SRCDIR "/forms/source/component/Date.cxx"))
  81             return false;
  82         if (loplugin::isSamePathname(fn, SRCDIR "/forms/source/component/Time.cxx"))
  83             return false;
  84         if (loplugin::isSamePathname(fn, SRCDIR "/svx/source/dialog/hyperdlg.cxx"))
  85             return false;
  86         if (loplugin::isSamePathname(fn, SRCDIR "/svx/source/dialog/rubydialog.cxx"))
  87             return false;
  88         if (loplugin::hasPathnamePrefix(fn, SRCDIR "/canvas/"))
  89             return false;
  90         if (loplugin::isSamePathname(fn, SRCDIR "/sc/source/ui/view/spelldialog.cxx"))
  91             return false;
  92         if (loplugin::isSamePathname(fn, SRCDIR "/sd/source/ui/dlg/SpellDialogChildWindow.cxx"))
  93             return false;
  94         // HAVE_ODBC_ADMINISTRATION
  95         if (loplugin::isSamePathname(fn, SRCDIR "/dbaccess/source/ui/dlg/dsselect.cxx"))
  96             return false;
  97         return true;
  98     }
  99
 100     virtual void run() override
 101     {
 102         if( preRun())
 103             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
 104     }
 105
 106     bool VisitCXXMethodDecl(const CXXMethodDecl *);
 107
 108 private:
 109     const CXXMethodDecl * findOverriddenOrSimilarMethodInSuperclasses(const CXXMethodDecl *);
 110     bool BaseCheckCallback(const CXXRecordDecl *BaseDefinition);
 111     CXXMemberCallExpr const * extractCallExpr(Expr const *);
 112 };
 113
 114 bool UnnecessaryOverride::VisitCXXMethodDecl(const CXXMethodDecl* methodDecl)
 115 {
 116     if (ignoreLocation(methodDecl->getCanonicalDecl())) {
 117         return true;
 118     }
 119     if (isa<CXXConstructorDecl>(methodDecl)) {
 120         return true;
 121     }
 122
 123     StringRef aFileName = getFilenameOfLocation(
 124         compiler.getSourceManager().getSpellingLoc(compat::getBeginLoc(methodDecl)));
 125
 126     if (isa<CXXDestructorDecl>(methodDecl)
 127        && !isInUnoIncludeFile(methodDecl))
 128     {
 129         // the code is this method is only __compiled__ if OSL_DEBUG_LEVEL > 1
 130         if (loplugin::isSamePathname(aFileName, SRCDIR "/tools/source/stream/strmunx.cxx"))
 131             return true;
 132
 133         // Warn about unnecessarily user-declared destructors.
 134         // A destructor is deemed unnecessary if:
 135         // * it is public;
 136         // * its class is only defined in the .cxx file (i.e., the virtual
 137         //   destructor is neither used to control the place of vtable
 138         //   emission, nor is its definition depending on types that may still
 139         //   be incomplete);
 140         //     or
 141         //   the destructor is inline, the class definition is complete,
 142         //     and the class has no superclasses
 143         // * it either does not have an explicit exception specification, or has
 144         //   a non-dependent explicit exception specification that is compatible
 145         //   with a non-dependent exception specification the destructor would
 146         //   have if it did not have an explicit one (TODO);
 147         // * it is either defined as defaulted or with an empty body.
 148         // Removing the user-declared destructor may cause the class to get an
 149         // implicitly declared move constructor and/or move assignment operator;
 150         // that is considered acceptable:  If any subobject cannot be moved, the
 151         // implicitly declared function will be defined as deleted (which is in
 152         // practice not much different from not having it declared), and
 153         // otherwise offering movability is likely even an improvement over not
 154         // offering it due to a "pointless" user-declared destructor.
 155         // Similarly, removing the user-declared destructor may cause the
 156         // implicit definition of a copy constructor and/or copy assignment
 157         // operator to change from being an obsolete feature to being a standard
 158         // feature.  That difference is not taken into account here.
 159         auto cls = methodDecl->getParent();
 160         if (methodDecl->getAccess() != AS_public)
 161         {
 162             return true;
 163         }
 164         if (!compiler.getSourceManager().isInMainFile(
 165                 methodDecl->getCanonicalDecl()->getLocation())
 166             && !( methodDecl->isInlined()))
 167         {
 168             return true;
 169         }
 170         // if it's virtual, but it has a base-class with a non-virtual destructor
 171         if (methodDecl->isVirtual())
 172         {
 173             bool baseWithVirtualDtor = false;
 174             for (auto baseSpecifier = cls->bases_begin(); baseSpecifier != cls->bases_end(); ++baseSpecifier)
 175             {
 176                 const RecordType* baseRecordType = baseSpecifier->getType()->getAs<RecordType>();
 177                 if (baseRecordType)
 178                 {
 179                     const CXXRecordDecl* baseRecordDecl = dyn_cast<CXXRecordDecl>(baseRecordType->getDecl());
 180                     if (baseRecordDecl && baseRecordDecl->getDestructor()
 181                         && baseRecordDecl->getDestructor()->isVirtual())
 182                     {
 183                         baseWithVirtualDtor = true;
 184                         break;
 185                     }
 186                 }
 187             }
 188             if (!baseWithVirtualDtor)
 189             {
 190                 return true;
 191             }
 192         }
 193         // corner case
 194         if (methodDecl->isInlined()
 195             && compiler.getSourceManager().isInMainFile(methodDecl->getLocation())
 196             && !compiler.getSourceManager().isInMainFile(methodDecl->getCanonicalDecl()->getLocation()))
 197         {
 198             return true;
 199         }
 200         if (!methodDecl->isExplicitlyDefaulted()) {
 201             if (!methodDecl->doesThisDeclarationHaveABody()
 202                 || methodDecl->isLateTemplateParsed())
 203             {
 204                 return true;
 205             }
 206             auto stmt = dyn_cast<CompoundStmt>(methodDecl->getBody());
 207             if (stmt == nullptr || stmt->size() != 0) {
 208                 return true;
 209             }
 210         }
 211         //TODO: exception specification
 212         if (!(cls->hasUserDeclaredCopyConstructor()
 213               || cls->hasUserDeclaredCopyAssignment()
 214               || cls->hasUserDeclaredMoveConstructor()
 215               || cls->hasUserDeclaredMoveAssignment()))
 216         {
 217         }
 218         if ((cls->needsImplicitMoveConstructor()
 219              && !(cls->hasUserDeclaredCopyConstructor()
 220                   || cls->hasUserDeclaredCopyAssignment()
 221                   || cls->hasUserDeclaredMoveAssignment()))
 222             || (cls->needsImplicitMoveAssignment()
 223                 && !(cls->hasUserDeclaredCopyConstructor()
 224                      || cls->hasUserDeclaredCopyAssignment()
 225                      || cls->hasUserDeclaredMoveConstructor())))
 226         {
 227             report(DiagnosticsEngine::Fatal, "TODO", methodDecl->getLocation());
 228             return true;
 229         }
 230         report(
 231             DiagnosticsEngine::Warning, "unnecessary user-declared destructor",
 232             methodDecl->getLocation())
 233             << methodDecl->getSourceRange();
 234         auto cd = methodDecl->getCanonicalDecl();
 235         if (cd->getLocation() != methodDecl->getLocation()) {
 236             report(DiagnosticsEngine::Note, "declared here", cd->getLocation())
 237                 << cd->getSourceRange();
 238         }
 239         return true;
 240     }
 241
 242     if (!methodDecl->doesThisDeclarationHaveABody()
 243         || methodDecl->isLateTemplateParsed())
 244     {
 245         return true;
 246     }
 247
 248     // If overriding more than one base member function, or one base member
 249     // function that is available in multiple (non-virtual) base class
 250     // instances, then this is a disambiguating override:
 251     if (methodDecl->isVirtual()) {
 252         if (methodDecl->size_overridden_methods() != 1)
 253         {
 254             return true;
 255         }
 256         if (hasMultipleBaseInstances(
 257                 methodDecl->getParent(),
 258                 (*methodDecl->begin_overridden_methods())->getParent()))
 259         {
 260             return true;
 261         }
 262     }
 263
 264     const CXXMethodDecl* overriddenMethodDecl = findOverriddenOrSimilarMethodInSuperclasses(methodDecl);
 265     if (!overriddenMethodDecl) {
 266         return true;
 267     }
 268
 269     // Check for differences in default parameters:
 270     unsigned const numParams = methodDecl->getNumParams();
 271     assert(overriddenMethodDecl->getNumParams() == numParams);
 272     for (unsigned i = 0; i != numParams; ++i) {
 273         if (checkIdenticalDefaultArguments(
 274                 methodDecl->getParamDecl(i)->getDefaultArg(),
 275                 overriddenMethodDecl->getParamDecl(i)->getDefaultArg())
 276             != IdenticalDefaultArgumentsResult::Yes)
 277         {
 278             return true;
 279         }
 280     }
 281
 282     if (methodDecl->getReturnType().getCanonicalType()
 283         != overriddenMethodDecl->getReturnType().getCanonicalType())
 284     {
 285         return true;
 286     }
 287
 288     //TODO: check for identical exception specifications
 289
 290     const CompoundStmt* compoundStmt = dyn_cast<CompoundStmt>(methodDecl->getBody());
 291     if (!compoundStmt || compoundStmt->size() > 2)
 292         return true;
 293
 294     const CXXMemberCallExpr* callExpr = nullptr;
 295     if (compoundStmt->size() == 1)
 296     {
 297         if (methodDecl->getReturnType().getCanonicalType()->isVoidType())
 298         {
 299             if (auto const e = dyn_cast<Expr>(*compoundStmt->body_begin())) {
 300                 callExpr = dyn_cast<CXXMemberCallExpr>(e->IgnoreImplicit()->IgnoreParens());
 301             }
 302         }
 303         else
 304         {
 305             auto returnStmt = dyn_cast<ReturnStmt>(*compoundStmt->body_begin());
 306             if (returnStmt == nullptr) {
 307                 return true;
 308             }
 309             auto returnExpr = returnStmt->getRetValue();
 310             if (returnExpr == nullptr) {
 311                 return true;
 312             }
 313             callExpr = extractCallExpr(returnExpr);
 314         }
 315     }
 316     else if (!methodDecl->getReturnType().getCanonicalType()->isVoidType())
 317     {
 318         /** handle constructions like
 319                bool foo() {
 320                 bool ret = Base::foo();
 321                 return ret;
 322             }
 323         */
 324         auto bodyIt = compoundStmt->body_begin();
 325         auto declStmt = dyn_cast<DeclStmt>(*bodyIt);
 326         if (!declStmt || !declStmt->isSingleDecl())
 327             return true;
 328         auto varDecl = dyn_cast<VarDecl>(declStmt->getSingleDecl());
 329         ++bodyIt;
 330         auto returnStmt = dyn_cast<ReturnStmt>(*bodyIt);
 331         if (!varDecl || !returnStmt)
 332             return true;
 333         Expr const * retValue = returnStmt->getRetValue()->IgnoreParenImpCasts();
 334         if (auto exprWithCleanups = dyn_cast<ExprWithCleanups>(retValue))
 335             retValue = exprWithCleanups->getSubExpr()->IgnoreParenImpCasts();
 336         if (auto constructExpr = dyn_cast<CXXConstructExpr>(retValue)) {
 337             if (constructExpr->getNumArgs() == 1)
 338                 retValue = constructExpr->getArg(0)->IgnoreParenImpCasts();
 339         }
 340         if (!isa<DeclRefExpr>(retValue))
 341             return true;
 342         callExpr = extractCallExpr(varDecl->getInit());
 343     }
 344
 345     if (!callExpr || callExpr->getMethodDecl() != overriddenMethodDecl)
 346         return true;
 347     const Expr* expr1 = callExpr->getImplicitObjectArgument()->IgnoreImpCasts();
 348     if (!expr1)
 349         return true;
 350     const CXXThisExpr* expr2 = dyn_cast_or_null<CXXThisExpr>(expr1);
 351     if (!expr2)
 352         return true;
 353     for (unsigned i = 0; i<callExpr->getNumArgs(); ++i) {
 354         auto e = callExpr->getArg(i)->IgnoreImplicit();
 355         if (auto const e1 = dyn_cast<CXXConstructExpr>(e)) {
 356             if (e1->getConstructor()->isCopyOrMoveConstructor() && e1->getNumArgs() == 1) {
 357                 e = e1->getArg(0)->IgnoreImpCasts();
 358             }
 359         }
 360         const DeclRefExpr * declRefExpr = dyn_cast<DeclRefExpr>(e);
 361         if (!declRefExpr || declRefExpr->getDecl() != methodDecl->getParamDecl(i))
 362             return true;
 363     }
 364
 365     const CXXMethodDecl* pOther = nullptr;
 366     if (methodDecl->getCanonicalDecl()->getLocation() != methodDecl->getLocation())
 367         pOther = methodDecl->getCanonicalDecl();
 368
 369     if (pOther) {
 370         StringRef aFileName = getFilenameOfLocation(
 371             compiler.getSourceManager().getSpellingLoc(compat::getBeginLoc(pOther)));
 372         // SFX_DECL_CHILDWINDOW_WITHID macro
 373         if (loplugin::isSamePathname(aFileName, SRCDIR "/include/sfx2/childwin.hxx"))
 374             return true;
 375     }
 376
 377     report(
 378             DiagnosticsEngine::Warning, "%0%1 function just calls %2 parent",
 379             methodDecl->getLocation())
 380         << methodDecl->getAccess()
 381         << (methodDecl->isVirtual() ? " virtual" : "")
 382         << overriddenMethodDecl->getAccess()
 383         << methodDecl->getSourceRange();
 384     if (methodDecl->getCanonicalDecl()->getLocation() != methodDecl->getLocation()) {
 385         const CXXMethodDecl* pOther = methodDecl->getCanonicalDecl();
 386         report(
 387             DiagnosticsEngine::Note,
 388             "method declaration here",
 389             pOther->getLocation())
 390           << pOther->getSourceRange();
 391     }
 392     return true;
 393 }
 394
 395 const CXXMethodDecl* UnnecessaryOverride::findOverriddenOrSimilarMethodInSuperclasses(const CXXMethodDecl* methodDecl)
 396 {
 397     if (methodDecl->isVirtual()) {
 398         return *methodDecl->begin_overridden_methods();
 399     }
 400     if (!methodDecl->getDeclName().isIdentifier()) {
 401         return nullptr;
 402     }
 403
 404     const CXXMethodDecl* similarMethod = nullptr;
 405     CXXBasePath similarBasePath;
 406
 407     auto BaseMatchesCallback = [&](const CXXBaseSpecifier *cxxBaseSpecifier, CXXBasePath& path)
 408     {
 409         if (cxxBaseSpecifier->getAccessSpecifier() != AS_public && cxxBaseSpecifier->getAccessSpecifier() != AS_protected)
 410             return false;
 411         if (!cxxBaseSpecifier->getType().getTypePtr())
 412             return false;
 413         const CXXRecordDecl* baseCXXRecordDecl = cxxBaseSpecifier->getType()->getAsCXXRecordDecl();
 414         if (!baseCXXRecordDecl)
 415             return false;
 416         if (baseCXXRecordDecl->isInvalidDecl())
 417             return false;
 418         for (const CXXMethodDecl* baseMethod : baseCXXRecordDecl->methods())
 419         {
 420             auto effectiveBaseMethodAccess = baseMethod->getAccess();
 421             if (effectiveBaseMethodAccess == AS_public && path.Access == AS_protected)
 422                 effectiveBaseMethodAccess = AS_protected;
 423             if (effectiveBaseMethodAccess != methodDecl->getAccess())
 424                 continue;
 425             if (!baseMethod->getDeclName().isIdentifier() || methodDecl->getName() != baseMethod->getName()) {
 426                 continue;
 427             }
 428             if (methodDecl->isStatic() != baseMethod->isStatic()
 429                 || methodDecl->isConst() != baseMethod->isConst()
 430                 || methodDecl->isVolatile() != baseMethod->isVolatile()
 431                 || (methodDecl->getRefQualifier()
 432                     != baseMethod->getRefQualifier())
 433                 || methodDecl->isVariadic() != baseMethod->isVariadic())
 434             {
 435                 continue;
 436             }
 437             if (methodDecl->getReturnType().getCanonicalType()
 438                 != baseMethod->getReturnType().getCanonicalType())
 439             {
 440                 continue;
 441             }
 442             if (methodDecl->getNumParams() != baseMethod->getNumParams())
 443                 continue;
 444             bool bParamsMatch = true;
 445             for (unsigned i=0; i<methodDecl->param_size(); ++i)
 446             {
 447                 if (methodDecl->parameters()[i]->getType() != baseMethod->parameters()[i]->getType())
 448                 {
 449                     bParamsMatch = false;
 450                     break;
 451                 }
 452             }
 453             if (bParamsMatch)
 454             {
 455                 // if we have already found a method directly below us in the inheritance hierarchy, just ignore this one
 456                 auto Compare = [&](CXXBasePathElement const & lhs, CXXBasePathElement const & rhs)
 457                 {
 458                     return lhs.Class == rhs.Class;
 459                 };
 460                 if (similarMethod
 461                     && similarBasePath.size() < path.size()
 462                     && std::equal(similarBasePath.begin(), similarBasePath.end(),
 463                                   path.begin(), Compare))
 464                     break;
 465                 if (similarMethod)
 466                     return true; // short circuit the process
 467                 similarMethod = baseMethod;
 468                 similarBasePath = path;
 469             }
 470         }
 471         return false;
 472     };
 473
 474     CXXBasePaths aPaths;
 475     if (methodDecl->getParent()->lookupInBases(BaseMatchesCallback, aPaths))
 476         return nullptr;
 477
 478     return similarMethod;
 479 }
 480
 481 CXXMemberCallExpr const * UnnecessaryOverride::extractCallExpr(Expr const *returnExpr)
 482 {
 483     returnExpr = returnExpr->IgnoreImplicit();
 484
 485     // In something like
 486     //
 487     //  Reference< XResultSet > SAL_CALL OPreparedStatement::executeQuery(
 488     //      const rtl::OUString& sql)
 489     //      throw(SQLException, RuntimeException, std::exception)
 490     //  {
 491     //      return OCommonStatement::executeQuery( sql );
 492     //  }
 493     //
 494     // look down through all the
 495     //
 496     //   ReturnStmt
 497     //   `-ExprWithCleanups
 498     //     `-CXXConstructExpr
 499     //      `-MaterializeTemporaryExpr
 500     //       `-ImplicitCastExpr
 501     //        `-CXXBindTemporaryExpr
 502     //         `-CXXMemberCallExpr
 503     //
 504     // where the fact that the overriding and overridden function have identical
 505     // return types makes us confident that all we need to check here is whether
 506     // there's an (arbitrary, one-argument) CXXConstructorExpr and
 507     // CXXBindTemporaryExpr in between:
 508     if (auto ctorExpr = dyn_cast<CXXConstructExpr>(returnExpr)) {
 509         if (ctorExpr->getNumArgs() == 1) {
 510             auto tempExpr1 = ctorExpr->getArg(0)->IgnoreImplicit();
 511             if (auto tempExpr2 = dyn_cast<CXXBindTemporaryExpr>(tempExpr1))
 512             {
 513                 returnExpr = tempExpr2->getSubExpr();
 514             }
 515             else if (auto tempExpr2 = dyn_cast<CXXMemberCallExpr>(tempExpr1))
 516             {
 517                 returnExpr = tempExpr2;
 518             }
 519         }
 520     }
 521
 522     return dyn_cast<CXXMemberCallExpr>(returnExpr->IgnoreParenImpCasts());
 523 }
 524
 525 loplugin::Plugin::Registration< UnnecessaryOverride > unnecessaryoverride("unnecessaryoverride", true);
 526
 527 }
 528
 529 #endif // LO_CLANG_SHARED_PLUGINS
 530
 531 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */