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().isiOS())
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->hasAttr<CFReturnsRetainedAttr>())
92         return true;
93 
94       if (FD->isGlobal() &&
95           FD->getIdentifier() &&
96           FD->getParent()->isTranslationUnit() &&
97           FD->isExternallyVisible() &&
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, bool IsDecl) {
126   SourceLocation SemiLoc = findSemiAfterLocation(loc, Ctx, IsDecl);
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                                             bool IsDecl) {
139   SourceManager &SM = Ctx.getSourceManager();
140   if (loc.isMacroID()) {
141     if (!Lexer::isAtEndOfMacroExpansion(loc, SM, Ctx.getLangOpts(), &loc))
142       return SourceLocation();
143   }
144   loc = Lexer::getLocForEndOfToken(loc, /*Offset=*/0, SM, Ctx.getLangOpts());
145 
146   // Break down the source location.
147   std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(loc);
148 
149   // Try to load the file buffer.
150   bool invalidTemp = false;
151   StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
152   if (invalidTemp)
153     return SourceLocation();
154 
155   const char *tokenBegin = file.data() + locInfo.second;
156 
157   // Lex from the start of the given location.
158   Lexer lexer(SM.getLocForStartOfFile(locInfo.first),
159               Ctx.getLangOpts(),
160               file.begin(), tokenBegin, file.end());
161   Token tok;
162   lexer.LexFromRawLexer(tok);
163   if (tok.isNot(tok::semi)) {
164     if (!IsDecl)
165       return SourceLocation();
166     // Declaration may be followed with other tokens; such as an __attribute,
167     // before ending with a semicolon.
168     return findSemiAfterLocation(tok.getLocation(), Ctx, /*IsDecl*/true);
169   }
170 
171   return tok.getLocation();
172 }
173 
174 bool trans::hasSideEffects(Expr *E, ASTContext &Ctx) {
175   if (!E || !E->HasSideEffects(Ctx))
176     return false;
177 
178   E = E->IgnoreParenCasts();
179   ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E);
180   if (!ME)
181     return true;
182   switch (ME->getMethodFamily()) {
183   case OMF_autorelease:
184   case OMF_dealloc:
185   case OMF_release:
186   case OMF_retain:
187     switch (ME->getReceiverKind()) {
188     case ObjCMessageExpr::SuperInstance:
189       return false;
190     case ObjCMessageExpr::Instance:
191       return hasSideEffects(ME->getInstanceReceiver(), Ctx);
192     default:
193       break;
194     }
195     break;
196   default:
197     break;
198   }
199 
200   return true;
201 }
202 
203 bool trans::isGlobalVar(Expr *E) {
204   E = E->IgnoreParenCasts();
205   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
206     return DRE->getDecl()->getDeclContext()->isFileContext() &&
207            DRE->getDecl()->isExternallyVisible();
208   if (ConditionalOperator *condOp = dyn_cast<ConditionalOperator>(E))
209     return isGlobalVar(condOp->getTrueExpr()) &&
210            isGlobalVar(condOp->getFalseExpr());
211 
212   return false;
213 }
214 
215 StringRef trans::getNilString(ASTContext &Ctx) {
216   if (Ctx.Idents.get("nil").hasMacroDefinition())
217     return "nil";
218   else
219     return "0";
220 }
221 
222 namespace {
223 
224 class ReferenceClear : public RecursiveASTVisitor<ReferenceClear> {
225   ExprSet &Refs;
226 public:
227   ReferenceClear(ExprSet &refs) : Refs(refs) { }
228   bool VisitDeclRefExpr(DeclRefExpr *E) { Refs.erase(E); return true; }
229 };
230 
231 class ReferenceCollector : public RecursiveASTVisitor<ReferenceCollector> {
232   ValueDecl *Dcl;
233   ExprSet &Refs;
234 
235 public:
236   ReferenceCollector(ValueDecl *D, ExprSet &refs)
237     : Dcl(D), Refs(refs) { }
238 
239   bool VisitDeclRefExpr(DeclRefExpr *E) {
240     if (E->getDecl() == Dcl)
241       Refs.insert(E);
242     return true;
243   }
244 };
245 
246 class RemovablesCollector : public RecursiveASTVisitor<RemovablesCollector> {
247   ExprSet &Removables;
248 
249 public:
250   RemovablesCollector(ExprSet &removables)
251   : Removables(removables) { }
252 
253   bool shouldWalkTypesOfTypeLocs() const { return false; }
254 
255   bool TraverseStmtExpr(StmtExpr *E) {
256     CompoundStmt *S = E->getSubStmt();
257     for (CompoundStmt::body_iterator
258         I = S->body_begin(), E = S->body_end(); I != E; ++I) {
259       if (I != E - 1)
260         mark(*I);
261       TraverseStmt(*I);
262     }
263     return true;
264   }
265 
266   bool VisitCompoundStmt(CompoundStmt *S) {
267     for (auto *I : S->body())
268       mark(I);
269     return true;
270   }
271 
272   bool VisitIfStmt(IfStmt *S) {
273     mark(S->getThen());
274     mark(S->getElse());
275     return true;
276   }
277 
278   bool VisitWhileStmt(WhileStmt *S) {
279     mark(S->getBody());
280     return true;
281   }
282 
283   bool VisitDoStmt(DoStmt *S) {
284     mark(S->getBody());
285     return true;
286   }
287 
288   bool VisitForStmt(ForStmt *S) {
289     mark(S->getInit());
290     mark(S->getInc());
291     mark(S->getBody());
292     return true;
293   }
294 
295 private:
296   void mark(Stmt *S) {
297     if (!S) return;
298 
299     while (LabelStmt *Label = dyn_cast<LabelStmt>(S))
300       S = Label->getSubStmt();
301     S = S->IgnoreImplicit();
302     if (Expr *E = dyn_cast<Expr>(S))
303       Removables.insert(E);
304   }
305 };
306 
307 } // end anonymous namespace
308 
309 void trans::clearRefsIn(Stmt *S, ExprSet &refs) {
310   ReferenceClear(refs).TraverseStmt(S);
311 }
312 
313 void trans::collectRefs(ValueDecl *D, Stmt *S, ExprSet &refs) {
314   ReferenceCollector(D, refs).TraverseStmt(S);
315 }
316 
317 void trans::collectRemovables(Stmt *S, ExprSet &exprs) {
318   RemovablesCollector(exprs).TraverseStmt(S);
319 }
320 
321 //===----------------------------------------------------------------------===//
322 // MigrationContext
323 //===----------------------------------------------------------------------===//
324 
325 namespace {
326 
327 class ASTTransform : public RecursiveASTVisitor<ASTTransform> {
328   MigrationContext &MigrateCtx;
329   typedef RecursiveASTVisitor<ASTTransform> base;
330 
331 public:
332   ASTTransform(MigrationContext &MigrateCtx) : MigrateCtx(MigrateCtx) { }
333 
334   bool shouldWalkTypesOfTypeLocs() const { return false; }
335 
336   bool TraverseObjCImplementationDecl(ObjCImplementationDecl *D) {
337     ObjCImplementationContext ImplCtx(MigrateCtx, D);
338     for (MigrationContext::traverser_iterator
339            I = MigrateCtx.traversers_begin(),
340            E = MigrateCtx.traversers_end(); I != E; ++I)
341       (*I)->traverseObjCImplementation(ImplCtx);
342 
343     return base::TraverseObjCImplementationDecl(D);
344   }
345 
346   bool TraverseStmt(Stmt *rootS) {
347     if (!rootS)
348       return true;
349 
350     BodyContext BodyCtx(MigrateCtx, rootS);
351     for (MigrationContext::traverser_iterator
352            I = MigrateCtx.traversers_begin(),
353            E = MigrateCtx.traversers_end(); I != E; ++I)
354       (*I)->traverseBody(BodyCtx);
355 
356     return true;
357   }
358 };
359 
360 }
361 
362 MigrationContext::~MigrationContext() {
363   for (traverser_iterator
364          I = traversers_begin(), E = traversers_end(); I != E; ++I)
365     delete *I;
366 }
367 
368 bool MigrationContext::isGCOwnedNonObjC(QualType T) {
369   while (!T.isNull()) {
370     if (const AttributedType *AttrT = T->getAs<AttributedType>()) {
371       if (AttrT->getAttrKind() == AttributedType::attr_objc_ownership)
372         return !AttrT->getModifiedType()->isObjCRetainableType();
373     }
374 
375     if (T->isArrayType())
376       T = Pass.Ctx.getBaseElementType(T);
377     else if (const PointerType *PT = T->getAs<PointerType>())
378       T = PT->getPointeeType();
379     else if (const ReferenceType *RT = T->getAs<ReferenceType>())
380       T = RT->getPointeeType();
381     else
382       break;
383   }
384 
385   return false;
386 }
387 
388 bool MigrationContext::rewritePropertyAttribute(StringRef fromAttr,
389                                                 StringRef toAttr,
390                                                 SourceLocation atLoc) {
391   if (atLoc.isMacroID())
392     return false;
393 
394   SourceManager &SM = Pass.Ctx.getSourceManager();
395 
396   // Break down the source location.
397   std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(atLoc);
398 
399   // Try to load the file buffer.
400   bool invalidTemp = false;
401   StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
402   if (invalidTemp)
403     return false;
404 
405   const char *tokenBegin = file.data() + locInfo.second;
406 
407   // Lex from the start of the given location.
408   Lexer lexer(SM.getLocForStartOfFile(locInfo.first),
409               Pass.Ctx.getLangOpts(),
410               file.begin(), tokenBegin, file.end());
411   Token tok;
412   lexer.LexFromRawLexer(tok);
413   if (tok.isNot(tok::at)) return false;
414   lexer.LexFromRawLexer(tok);
415   if (tok.isNot(tok::raw_identifier)) return false;
416   if (StringRef(tok.getRawIdentifierData(), tok.getLength())
417         != "property")
418     return false;
419   lexer.LexFromRawLexer(tok);
420   if (tok.isNot(tok::l_paren)) return false;
421 
422   Token BeforeTok = tok;
423   Token AfterTok;
424   AfterTok.startToken();
425   SourceLocation AttrLoc;
426 
427   lexer.LexFromRawLexer(tok);
428   if (tok.is(tok::r_paren))
429     return false;
430 
431   while (1) {
432     if (tok.isNot(tok::raw_identifier)) return false;
433     StringRef ident(tok.getRawIdentifierData(), tok.getLength());
434     if (ident == fromAttr) {
435       if (!toAttr.empty()) {
436         Pass.TA.replaceText(tok.getLocation(), fromAttr, toAttr);
437         return true;
438       }
439       // We want to remove the attribute.
440       AttrLoc = tok.getLocation();
441     }
442 
443     do {
444       lexer.LexFromRawLexer(tok);
445       if (AttrLoc.isValid() && AfterTok.is(tok::unknown))
446         AfterTok = tok;
447     } while (tok.isNot(tok::comma) && tok.isNot(tok::r_paren));
448     if (tok.is(tok::r_paren))
449       break;
450     if (AttrLoc.isInvalid())
451       BeforeTok = tok;
452     lexer.LexFromRawLexer(tok);
453   }
454 
455   if (toAttr.empty() && AttrLoc.isValid() && AfterTok.isNot(tok::unknown)) {
456     // We want to remove the attribute.
457     if (BeforeTok.is(tok::l_paren) && AfterTok.is(tok::r_paren)) {
458       Pass.TA.remove(SourceRange(BeforeTok.getLocation(),
459                                  AfterTok.getLocation()));
460     } else if (BeforeTok.is(tok::l_paren) && AfterTok.is(tok::comma)) {
461       Pass.TA.remove(SourceRange(AttrLoc, AfterTok.getLocation()));
462     } else {
463       Pass.TA.remove(SourceRange(BeforeTok.getLocation(), AttrLoc));
464     }
465 
466     return true;
467   }
468 
469   return false;
470 }
471 
472 bool MigrationContext::addPropertyAttribute(StringRef attr,
473                                             SourceLocation atLoc) {
474   if (atLoc.isMacroID())
475     return false;
476 
477   SourceManager &SM = Pass.Ctx.getSourceManager();
478 
479   // Break down the source location.
480   std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(atLoc);
481 
482   // Try to load the file buffer.
483   bool invalidTemp = false;
484   StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
485   if (invalidTemp)
486     return false;
487 
488   const char *tokenBegin = file.data() + locInfo.second;
489 
490   // Lex from the start of the given location.
491   Lexer lexer(SM.getLocForStartOfFile(locInfo.first),
492               Pass.Ctx.getLangOpts(),
493               file.begin(), tokenBegin, file.end());
494   Token tok;
495   lexer.LexFromRawLexer(tok);
496   if (tok.isNot(tok::at)) return false;
497   lexer.LexFromRawLexer(tok);
498   if (tok.isNot(tok::raw_identifier)) return false;
499   if (StringRef(tok.getRawIdentifierData(), tok.getLength())
500         != "property")
501     return false;
502   lexer.LexFromRawLexer(tok);
503 
504   if (tok.isNot(tok::l_paren)) {
505     Pass.TA.insert(tok.getLocation(), std::string("(") + attr.str() + ") ");
506     return true;
507   }
508 
509   lexer.LexFromRawLexer(tok);
510   if (tok.is(tok::r_paren)) {
511     Pass.TA.insert(tok.getLocation(), attr);
512     return true;
513   }
514 
515   if (tok.isNot(tok::raw_identifier)) return false;
516 
517   Pass.TA.insert(tok.getLocation(), std::string(attr) + ", ");
518   return true;
519 }
520 
521 void MigrationContext::traverse(TranslationUnitDecl *TU) {
522   for (traverser_iterator
523          I = traversers_begin(), E = traversers_end(); I != E; ++I)
524     (*I)->traverseTU(*this);
525 
526   ASTTransform(*this).TraverseDecl(TU);
527 }
528 
529 static void GCRewriteFinalize(MigrationPass &pass) {
530   ASTContext &Ctx = pass.Ctx;
531   TransformActions &TA = pass.TA;
532   DeclContext *DC = Ctx.getTranslationUnitDecl();
533   Selector FinalizeSel =
534    Ctx.Selectors.getNullarySelector(&pass.Ctx.Idents.get("finalize"));
535 
536   typedef DeclContext::specific_decl_iterator<ObjCImplementationDecl>
537   impl_iterator;
538   for (impl_iterator I = impl_iterator(DC->decls_begin()),
539        E = impl_iterator(DC->decls_end()); I != E; ++I) {
540     for (const auto *MD : I->instance_methods()) {
541       if (!MD->hasBody())
542         continue;
543 
544       if (MD->isInstanceMethod() && MD->getSelector() == FinalizeSel) {
545         const ObjCMethodDecl *FinalizeM = MD;
546         Transaction Trans(TA);
547         TA.insert(FinalizeM->getSourceRange().getBegin(),
548                   "#if !__has_feature(objc_arc)\n");
549         CharSourceRange::getTokenRange(FinalizeM->getSourceRange());
550         const SourceManager &SM = pass.Ctx.getSourceManager();
551         const LangOptions &LangOpts = pass.Ctx.getLangOpts();
552         bool Invalid;
553         std::string str = "\n#endif\n";
554         str += Lexer::getSourceText(
555                   CharSourceRange::getTokenRange(FinalizeM->getSourceRange()),
556                                     SM, LangOpts, &Invalid);
557         TA.insertAfterToken(FinalizeM->getSourceRange().getEnd(), str);
558 
559         break;
560       }
561     }
562   }
563 }
564 
565 //===----------------------------------------------------------------------===//
566 // getAllTransformations.
567 //===----------------------------------------------------------------------===//
568 
569 static void traverseAST(MigrationPass &pass) {
570   MigrationContext MigrateCtx(pass);
571 
572   if (pass.isGCMigration()) {
573     MigrateCtx.addTraverser(new GCCollectableCallsTraverser);
574     MigrateCtx.addTraverser(new GCAttrsTraverser());
575   }
576   MigrateCtx.addTraverser(new PropertyRewriteTraverser());
577   MigrateCtx.addTraverser(new BlockObjCVariableTraverser());
578   MigrateCtx.addTraverser(new ProtectedScopeTraverser());
579 
580   MigrateCtx.traverse(pass.Ctx.getTranslationUnitDecl());
581 }
582 
583 static void independentTransforms(MigrationPass &pass) {
584   rewriteAutoreleasePool(pass);
585   removeRetainReleaseDeallocFinalize(pass);
586   rewriteUnusedInitDelegate(pass);
587   removeZeroOutPropsInDeallocFinalize(pass);
588   makeAssignARCSafe(pass);
589   rewriteUnbridgedCasts(pass);
590   checkAPIUses(pass);
591   traverseAST(pass);
592 }
593 
594 std::vector<TransformFn> arcmt::getAllTransformations(
595                                                LangOptions::GCMode OrigGCMode,
596                                                bool NoFinalizeRemoval) {
597   std::vector<TransformFn> transforms;
598 
599   if (OrigGCMode ==  LangOptions::GCOnly && NoFinalizeRemoval)
600     transforms.push_back(GCRewriteFinalize);
601   transforms.push_back(independentTransforms);
602   // This depends on previous transformations removing various expressions.
603   transforms.push_back(removeEmptyStatementsAndDeallocFinalize);
604 
605   return transforms;
606 }
607