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      1 //===--- Transforms.cpp - Transformations to ARC mode ---------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "Transforms.h"
     11 #include "Internals.h"
     12 #include "clang/AST/ASTContext.h"
     13 #include "clang/AST/RecursiveASTVisitor.h"
     14 #include "clang/AST/StmtVisitor.h"
     15 #include "clang/Analysis/DomainSpecific/CocoaConventions.h"
     16 #include "clang/Basic/SourceManager.h"
     17 #include "clang/Basic/TargetInfo.h"
     18 #include "clang/Lex/Lexer.h"
     19 #include "clang/Sema/Sema.h"
     20 #include "clang/Sema/SemaDiagnostic.h"
     21 #include "llvm/ADT/DenseSet.h"
     22 #include "llvm/ADT/StringSwitch.h"
     23 #include <map>
     24 
     25 using namespace clang;
     26 using namespace arcmt;
     27 using namespace trans;
     28 
     29 ASTTraverser::~ASTTraverser() { }
     30 
     31 bool MigrationPass::CFBridgingFunctionsDefined() {
     32   if (!EnableCFBridgeFns.hasValue())
     33     EnableCFBridgeFns = SemaRef.isKnownName("CFBridgingRetain") &&
     34                         SemaRef.isKnownName("CFBridgingRelease");
     35   return *EnableCFBridgeFns;
     36 }
     37 
     38 //===----------------------------------------------------------------------===//
     39 // Helpers.
     40 //===----------------------------------------------------------------------===//
     41 
     42 bool trans::canApplyWeak(ASTContext &Ctx, QualType type,
     43                          bool AllowOnUnknownClass) {
     44   if (!Ctx.getLangOpts().ObjCARCWeak)
     45     return false;
     46 
     47   QualType T = type;
     48   if (T.isNull())
     49     return false;
     50 
     51   // iOS is always safe to use 'weak'.
     52   if (Ctx.getTargetInfo().getTriple().getOS() == llvm::Triple::IOS)
     53     AllowOnUnknownClass = true;
     54 
     55   while (const PointerType *ptr = T->getAs<PointerType>())
     56     T = ptr->getPointeeType();
     57   if (const ObjCObjectPointerType *ObjT = T->getAs<ObjCObjectPointerType>()) {
     58     ObjCInterfaceDecl *Class = ObjT->getInterfaceDecl();
     59     if (!AllowOnUnknownClass && (!Class || Class->getName() == "NSObject"))
     60       return false; // id/NSObject is not safe for weak.
     61     if (!AllowOnUnknownClass && !Class->hasDefinition())
     62       return false; // forward classes are not verifiable, therefore not safe.
     63     if (Class && Class->isArcWeakrefUnavailable())
     64       return false;
     65   }
     66 
     67   return true;
     68 }
     69 
     70 bool trans::isPlusOneAssign(const BinaryOperator *E) {
     71   if (E->getOpcode() != BO_Assign)
     72     return false;
     73 
     74   return isPlusOne(E->getRHS());
     75 }
     76 
     77 bool trans::isPlusOne(const Expr *E) {
     78   if (!E)
     79     return false;
     80   if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(E))
     81     E = EWC->getSubExpr();
     82 
     83   if (const ObjCMessageExpr *
     84         ME = dyn_cast<ObjCMessageExpr>(E->IgnoreParenCasts()))
     85     if (ME->getMethodFamily() == OMF_retain)
     86       return true;
     87 
     88   if (const CallExpr *
     89         callE = dyn_cast<CallExpr>(E->IgnoreParenCasts())) {
     90     if (const FunctionDecl *FD = callE->getDirectCallee()) {
     91       if (FD->getAttr<CFReturnsRetainedAttr>())
     92         return true;
     93 
     94       if (FD->isGlobal() &&
     95           FD->getIdentifier() &&
     96           FD->getParent()->isTranslationUnit() &&
     97           FD->hasExternalLinkage() &&
     98           ento::cocoa::isRefType(callE->getType(), "CF",
     99                                  FD->getIdentifier()->getName())) {
    100         StringRef fname = FD->getIdentifier()->getName();
    101         if (fname.endswith("Retain") ||
    102             fname.find("Create") != StringRef::npos ||
    103             fname.find("Copy") != StringRef::npos) {
    104           return true;
    105         }
    106       }
    107     }
    108   }
    109 
    110   const ImplicitCastExpr *implCE = dyn_cast<ImplicitCastExpr>(E);
    111   while (implCE && implCE->getCastKind() ==  CK_BitCast)
    112     implCE = dyn_cast<ImplicitCastExpr>(implCE->getSubExpr());
    113 
    114   if (implCE && implCE->getCastKind() == CK_ARCConsumeObject)
    115     return true;
    116 
    117   return false;
    118 }
    119 
    120 /// \brief 'Loc' is the end of a statement range. This returns the location
    121 /// immediately after the semicolon following the statement.
    122 /// If no semicolon is found or the location is inside a macro, the returned
    123 /// source location will be invalid.
    124 SourceLocation trans::findLocationAfterSemi(SourceLocation loc,
    125                                             ASTContext &Ctx) {
    126   SourceLocation SemiLoc = findSemiAfterLocation(loc, Ctx);
    127   if (SemiLoc.isInvalid())
    128     return SourceLocation();
    129   return SemiLoc.getLocWithOffset(1);
    130 }
    131 
    132 /// \brief \arg Loc is the end of a statement range. This returns the location
    133 /// of the semicolon following the statement.
    134 /// If no semicolon is found or the location is inside a macro, the returned
    135 /// source location will be invalid.
    136 SourceLocation trans::findSemiAfterLocation(SourceLocation loc,
    137                                             ASTContext &Ctx) {
    138   SourceManager &SM = Ctx.getSourceManager();
    139   if (loc.isMacroID()) {
    140     if (!Lexer::isAtEndOfMacroExpansion(loc, SM, Ctx.getLangOpts(), &loc))
    141       return SourceLocation();
    142   }
    143   loc = Lexer::getLocForEndOfToken(loc, /*Offset=*/0, SM, Ctx.getLangOpts());
    144 
    145   // Break down the source location.
    146   std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(loc);
    147 
    148   // Try to load the file buffer.
    149   bool invalidTemp = false;
    150   StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
    151   if (invalidTemp)
    152     return SourceLocation();
    153 
    154   const char *tokenBegin = file.data() + locInfo.second;
    155 
    156   // Lex from the start of the given location.
    157   Lexer lexer(SM.getLocForStartOfFile(locInfo.first),
    158               Ctx.getLangOpts(),
    159               file.begin(), tokenBegin, file.end());
    160   Token tok;
    161   lexer.LexFromRawLexer(tok);
    162   if (tok.isNot(tok::semi))
    163     return SourceLocation();
    164 
    165   return tok.getLocation();
    166 }
    167 
    168 bool trans::hasSideEffects(Expr *E, ASTContext &Ctx) {
    169   if (!E || !E->HasSideEffects(Ctx))
    170     return false;
    171 
    172   E = E->IgnoreParenCasts();
    173   ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E);
    174   if (!ME)
    175     return true;
    176   switch (ME->getMethodFamily()) {
    177   case OMF_autorelease:
    178   case OMF_dealloc:
    179   case OMF_release:
    180   case OMF_retain:
    181     switch (ME->getReceiverKind()) {
    182     case ObjCMessageExpr::SuperInstance:
    183       return false;
    184     case ObjCMessageExpr::Instance:
    185       return hasSideEffects(ME->getInstanceReceiver(), Ctx);
    186     default:
    187       break;
    188     }
    189     break;
    190   default:
    191     break;
    192   }
    193 
    194   return true;
    195 }
    196 
    197 bool trans::isGlobalVar(Expr *E) {
    198   E = E->IgnoreParenCasts();
    199   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
    200     return DRE->getDecl()->getDeclContext()->isFileContext() &&
    201            DRE->getDecl()->hasExternalLinkage();
    202   if (ConditionalOperator *condOp = dyn_cast<ConditionalOperator>(E))
    203     return isGlobalVar(condOp->getTrueExpr()) &&
    204            isGlobalVar(condOp->getFalseExpr());
    205 
    206   return false;
    207 }
    208 
    209 StringRef trans::getNilString(ASTContext &Ctx) {
    210   if (Ctx.Idents.get("nil").hasMacroDefinition())
    211     return "nil";
    212   else
    213     return "0";
    214 }
    215 
    216 namespace {
    217 
    218 class ReferenceClear : public RecursiveASTVisitor<ReferenceClear> {
    219   ExprSet &Refs;
    220 public:
    221   ReferenceClear(ExprSet &refs) : Refs(refs) { }
    222   bool VisitDeclRefExpr(DeclRefExpr *E) { Refs.erase(E); return true; }
    223 };
    224 
    225 class ReferenceCollector : public RecursiveASTVisitor<ReferenceCollector> {
    226   ValueDecl *Dcl;
    227   ExprSet &Refs;
    228 
    229 public:
    230   ReferenceCollector(ValueDecl *D, ExprSet &refs)
    231     : Dcl(D), Refs(refs) { }
    232 
    233   bool VisitDeclRefExpr(DeclRefExpr *E) {
    234     if (E->getDecl() == Dcl)
    235       Refs.insert(E);
    236     return true;
    237   }
    238 };
    239 
    240 class RemovablesCollector : public RecursiveASTVisitor<RemovablesCollector> {
    241   ExprSet &Removables;
    242 
    243 public:
    244   RemovablesCollector(ExprSet &removables)
    245   : Removables(removables) { }
    246 
    247   bool shouldWalkTypesOfTypeLocs() const { return false; }
    248 
    249   bool TraverseStmtExpr(StmtExpr *E) {
    250     CompoundStmt *S = E->getSubStmt();
    251     for (CompoundStmt::body_iterator
    252         I = S->body_begin(), E = S->body_end(); I != E; ++I) {
    253       if (I != E - 1)
    254         mark(*I);
    255       TraverseStmt(*I);
    256     }
    257     return true;
    258   }
    259 
    260   bool VisitCompoundStmt(CompoundStmt *S) {
    261     for (CompoundStmt::body_iterator
    262         I = S->body_begin(), E = S->body_end(); I != E; ++I)
    263       mark(*I);
    264     return true;
    265   }
    266 
    267   bool VisitIfStmt(IfStmt *S) {
    268     mark(S->getThen());
    269     mark(S->getElse());
    270     return true;
    271   }
    272 
    273   bool VisitWhileStmt(WhileStmt *S) {
    274     mark(S->getBody());
    275     return true;
    276   }
    277 
    278   bool VisitDoStmt(DoStmt *S) {
    279     mark(S->getBody());
    280     return true;
    281   }
    282 
    283   bool VisitForStmt(ForStmt *S) {
    284     mark(S->getInit());
    285     mark(S->getInc());
    286     mark(S->getBody());
    287     return true;
    288   }
    289 
    290 private:
    291   void mark(Stmt *S) {
    292     if (!S) return;
    293 
    294     while (LabelStmt *Label = dyn_cast<LabelStmt>(S))
    295       S = Label->getSubStmt();
    296     S = S->IgnoreImplicit();
    297     if (Expr *E = dyn_cast<Expr>(S))
    298       Removables.insert(E);
    299   }
    300 };
    301 
    302 } // end anonymous namespace
    303 
    304 void trans::clearRefsIn(Stmt *S, ExprSet &refs) {
    305   ReferenceClear(refs).TraverseStmt(S);
    306 }
    307 
    308 void trans::collectRefs(ValueDecl *D, Stmt *S, ExprSet &refs) {
    309   ReferenceCollector(D, refs).TraverseStmt(S);
    310 }
    311 
    312 void trans::collectRemovables(Stmt *S, ExprSet &exprs) {
    313   RemovablesCollector(exprs).TraverseStmt(S);
    314 }
    315 
    316 //===----------------------------------------------------------------------===//
    317 // MigrationContext
    318 //===----------------------------------------------------------------------===//
    319 
    320 namespace {
    321 
    322 class ASTTransform : public RecursiveASTVisitor<ASTTransform> {
    323   MigrationContext &MigrateCtx;
    324   typedef RecursiveASTVisitor<ASTTransform> base;
    325 
    326 public:
    327   ASTTransform(MigrationContext &MigrateCtx) : MigrateCtx(MigrateCtx) { }
    328 
    329   bool shouldWalkTypesOfTypeLocs() const { return false; }
    330 
    331   bool TraverseObjCImplementationDecl(ObjCImplementationDecl *D) {
    332     ObjCImplementationContext ImplCtx(MigrateCtx, D);
    333     for (MigrationContext::traverser_iterator
    334            I = MigrateCtx.traversers_begin(),
    335            E = MigrateCtx.traversers_end(); I != E; ++I)
    336       (*I)->traverseObjCImplementation(ImplCtx);
    337 
    338     return base::TraverseObjCImplementationDecl(D);
    339   }
    340 
    341   bool TraverseStmt(Stmt *rootS) {
    342     if (!rootS)
    343       return true;
    344 
    345     BodyContext BodyCtx(MigrateCtx, rootS);
    346     for (MigrationContext::traverser_iterator
    347            I = MigrateCtx.traversers_begin(),
    348            E = MigrateCtx.traversers_end(); I != E; ++I)
    349       (*I)->traverseBody(BodyCtx);
    350 
    351     return true;
    352   }
    353 };
    354 
    355 }
    356 
    357 MigrationContext::~MigrationContext() {
    358   for (traverser_iterator
    359          I = traversers_begin(), E = traversers_end(); I != E; ++I)
    360     delete *I;
    361 }
    362 
    363 bool MigrationContext::isGCOwnedNonObjC(QualType T) {
    364   while (!T.isNull()) {
    365     if (const AttributedType *AttrT = T->getAs<AttributedType>()) {
    366       if (AttrT->getAttrKind() == AttributedType::attr_objc_ownership)
    367         return !AttrT->getModifiedType()->isObjCRetainableType();
    368     }
    369 
    370     if (T->isArrayType())
    371       T = Pass.Ctx.getBaseElementType(T);
    372     else if (const PointerType *PT = T->getAs<PointerType>())
    373       T = PT->getPointeeType();
    374     else if (const ReferenceType *RT = T->getAs<ReferenceType>())
    375       T = RT->getPointeeType();
    376     else
    377       break;
    378   }
    379 
    380   return false;
    381 }
    382 
    383 bool MigrationContext::rewritePropertyAttribute(StringRef fromAttr,
    384                                                 StringRef toAttr,
    385                                                 SourceLocation atLoc) {
    386   if (atLoc.isMacroID())
    387     return false;
    388 
    389   SourceManager &SM = Pass.Ctx.getSourceManager();
    390 
    391   // Break down the source location.
    392   std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(atLoc);
    393 
    394   // Try to load the file buffer.
    395   bool invalidTemp = false;
    396   StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
    397   if (invalidTemp)
    398     return false;
    399 
    400   const char *tokenBegin = file.data() + locInfo.second;
    401 
    402   // Lex from the start of the given location.
    403   Lexer lexer(SM.getLocForStartOfFile(locInfo.first),
    404               Pass.Ctx.getLangOpts(),
    405               file.begin(), tokenBegin, file.end());
    406   Token tok;
    407   lexer.LexFromRawLexer(tok);
    408   if (tok.isNot(tok::at)) return false;
    409   lexer.LexFromRawLexer(tok);
    410   if (tok.isNot(tok::raw_identifier)) return false;
    411   if (StringRef(tok.getRawIdentifierData(), tok.getLength())
    412         != "property")
    413     return false;
    414   lexer.LexFromRawLexer(tok);
    415   if (tok.isNot(tok::l_paren)) return false;
    416 
    417   Token BeforeTok = tok;
    418   Token AfterTok;
    419   AfterTok.startToken();
    420   SourceLocation AttrLoc;
    421 
    422   lexer.LexFromRawLexer(tok);
    423   if (tok.is(tok::r_paren))
    424     return false;
    425 
    426   while (1) {
    427     if (tok.isNot(tok::raw_identifier)) return false;
    428     StringRef ident(tok.getRawIdentifierData(), tok.getLength());
    429     if (ident == fromAttr) {
    430       if (!toAttr.empty()) {
    431         Pass.TA.replaceText(tok.getLocation(), fromAttr, toAttr);
    432         return true;
    433       }
    434       // We want to remove the attribute.
    435       AttrLoc = tok.getLocation();
    436     }
    437 
    438     do {
    439       lexer.LexFromRawLexer(tok);
    440       if (AttrLoc.isValid() && AfterTok.is(tok::unknown))
    441         AfterTok = tok;
    442     } while (tok.isNot(tok::comma) && tok.isNot(tok::r_paren));
    443     if (tok.is(tok::r_paren))
    444       break;
    445     if (AttrLoc.isInvalid())
    446       BeforeTok = tok;
    447     lexer.LexFromRawLexer(tok);
    448   }
    449 
    450   if (toAttr.empty() && AttrLoc.isValid() && AfterTok.isNot(tok::unknown)) {
    451     // We want to remove the attribute.
    452     if (BeforeTok.is(tok::l_paren) && AfterTok.is(tok::r_paren)) {
    453       Pass.TA.remove(SourceRange(BeforeTok.getLocation(),
    454                                  AfterTok.getLocation()));
    455     } else if (BeforeTok.is(tok::l_paren) && AfterTok.is(tok::comma)) {
    456       Pass.TA.remove(SourceRange(AttrLoc, AfterTok.getLocation()));
    457     } else {
    458       Pass.TA.remove(SourceRange(BeforeTok.getLocation(), AttrLoc));
    459     }
    460 
    461     return true;
    462   }
    463 
    464   return false;
    465 }
    466 
    467 bool MigrationContext::addPropertyAttribute(StringRef attr,
    468                                             SourceLocation atLoc) {
    469   if (atLoc.isMacroID())
    470     return false;
    471 
    472   SourceManager &SM = Pass.Ctx.getSourceManager();
    473 
    474   // Break down the source location.
    475   std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(atLoc);
    476 
    477   // Try to load the file buffer.
    478   bool invalidTemp = false;
    479   StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
    480   if (invalidTemp)
    481     return false;
    482 
    483   const char *tokenBegin = file.data() + locInfo.second;
    484 
    485   // Lex from the start of the given location.
    486   Lexer lexer(SM.getLocForStartOfFile(locInfo.first),
    487               Pass.Ctx.getLangOpts(),
    488               file.begin(), tokenBegin, file.end());
    489   Token tok;
    490   lexer.LexFromRawLexer(tok);
    491   if (tok.isNot(tok::at)) return false;
    492   lexer.LexFromRawLexer(tok);
    493   if (tok.isNot(tok::raw_identifier)) return false;
    494   if (StringRef(tok.getRawIdentifierData(), tok.getLength())
    495         != "property")
    496     return false;
    497   lexer.LexFromRawLexer(tok);
    498 
    499   if (tok.isNot(tok::l_paren)) {
    500     Pass.TA.insert(tok.getLocation(), std::string("(") + attr.str() + ") ");
    501     return true;
    502   }
    503 
    504   lexer.LexFromRawLexer(tok);
    505   if (tok.is(tok::r_paren)) {
    506     Pass.TA.insert(tok.getLocation(), attr);
    507     return true;
    508   }
    509 
    510   if (tok.isNot(tok::raw_identifier)) return false;
    511 
    512   Pass.TA.insert(tok.getLocation(), std::string(attr) + ", ");
    513   return true;
    514 }
    515 
    516 void MigrationContext::traverse(TranslationUnitDecl *TU) {
    517   for (traverser_iterator
    518          I = traversers_begin(), E = traversers_end(); I != E; ++I)
    519     (*I)->traverseTU(*this);
    520 
    521   ASTTransform(*this).TraverseDecl(TU);
    522 }
    523 
    524 static void GCRewriteFinalize(MigrationPass &pass) {
    525   ASTContext &Ctx = pass.Ctx;
    526   TransformActions &TA = pass.TA;
    527   DeclContext *DC = Ctx.getTranslationUnitDecl();
    528   Selector FinalizeSel =
    529    Ctx.Selectors.getNullarySelector(&pass.Ctx.Idents.get("finalize"));
    530 
    531   typedef DeclContext::specific_decl_iterator<ObjCImplementationDecl>
    532   impl_iterator;
    533   for (impl_iterator I = impl_iterator(DC->decls_begin()),
    534        E = impl_iterator(DC->decls_end()); I != E; ++I) {
    535     for (ObjCImplementationDecl::instmeth_iterator
    536          MI = I->instmeth_begin(),
    537          ME = I->instmeth_end(); MI != ME; ++MI) {
    538       ObjCMethodDecl *MD = *MI;
    539       if (!MD->hasBody())
    540         continue;
    541 
    542       if (MD->isInstanceMethod() && MD->getSelector() == FinalizeSel) {
    543         ObjCMethodDecl *FinalizeM = MD;
    544         Transaction Trans(TA);
    545         TA.insert(FinalizeM->getSourceRange().getBegin(),
    546                   "#if !__has_feature(objc_arc)\n");
    547         CharSourceRange::getTokenRange(FinalizeM->getSourceRange());
    548         const SourceManager &SM = pass.Ctx.getSourceManager();
    549         const LangOptions &LangOpts = pass.Ctx.getLangOpts();
    550         bool Invalid;
    551         std::string str = "\n#endif\n";
    552         str += Lexer::getSourceText(
    553                   CharSourceRange::getTokenRange(FinalizeM->getSourceRange()),
    554                                     SM, LangOpts, &Invalid);
    555         TA.insertAfterToken(FinalizeM->getSourceRange().getEnd(), str);
    556 
    557         break;
    558       }
    559     }
    560   }
    561 }
    562 
    563 //===----------------------------------------------------------------------===//
    564 // getAllTransformations.
    565 //===----------------------------------------------------------------------===//
    566 
    567 static void traverseAST(MigrationPass &pass) {
    568   MigrationContext MigrateCtx(pass);
    569 
    570   if (pass.isGCMigration()) {
    571     MigrateCtx.addTraverser(new GCCollectableCallsTraverser);
    572     MigrateCtx.addTraverser(new GCAttrsTraverser());
    573   }
    574   MigrateCtx.addTraverser(new PropertyRewriteTraverser());
    575   MigrateCtx.addTraverser(new BlockObjCVariableTraverser());
    576   MigrateCtx.addTraverser(new ProtectedScopeTraverser());
    577 
    578   MigrateCtx.traverse(pass.Ctx.getTranslationUnitDecl());
    579 }
    580 
    581 static void independentTransforms(MigrationPass &pass) {
    582   rewriteAutoreleasePool(pass);
    583   removeRetainReleaseDeallocFinalize(pass);
    584   rewriteUnusedInitDelegate(pass);
    585   removeZeroOutPropsInDeallocFinalize(pass);
    586   makeAssignARCSafe(pass);
    587   rewriteUnbridgedCasts(pass);
    588   checkAPIUses(pass);
    589   traverseAST(pass);
    590 }
    591 
    592 std::vector<TransformFn> arcmt::getAllTransformations(
    593                                                LangOptions::GCMode OrigGCMode,
    594                                                bool NoFinalizeRemoval) {
    595   std::vector<TransformFn> transforms;
    596 
    597   if (OrigGCMode ==  LangOptions::GCOnly && NoFinalizeRemoval)
    598     transforms.push_back(GCRewriteFinalize);
    599   transforms.push_back(independentTransforms);
    600   // This depends on previous transformations removing various expressions.
    601   transforms.push_back(removeEmptyStatementsAndDeallocFinalize);
    602 
    603   return transforms;
    604 }
    605