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