TransUnbridgedCasts.cpp revision 651f13cea278ec967336033dd032faef0e9fc2ec 
1//===--- TransUnbridgedCasts.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// rewriteUnbridgedCasts:
11//
12// A cast of non-objc pointer to an objc one is checked. If the non-objc pointer
13// is from a file-level variable, __bridge cast is used to convert it.
14// For the result of a function call that we know is +1/+0,
15// __bridge/CFBridgingRelease is used.
16//
17//  NSString *str = (NSString *)kUTTypePlainText;
18//  str = b ? kUTTypeRTF : kUTTypePlainText;
19//  NSString *_uuidString = (NSString *)CFUUIDCreateString(kCFAllocatorDefault,
20//                                                         _uuid);
21// ---->
22//  NSString *str = (__bridge NSString *)kUTTypePlainText;
23//  str = (__bridge NSString *)(b ? kUTTypeRTF : kUTTypePlainText);
24// NSString *_uuidString = (NSString *)
25//            CFBridgingRelease(CFUUIDCreateString(kCFAllocatorDefault, _uuid));
26//
27// For a C pointer to ObjC, for casting 'self', __bridge is used.
28//
29//  CFStringRef str = (CFStringRef)self;
30// ---->
31//  CFStringRef str = (__bridge CFStringRef)self;
32//
33// Uses of Block_copy/Block_release macros are rewritten:
34//
35//  c = Block_copy(b);
36//  Block_release(c);
37// ---->
38//  c = [b copy];
39//  <removed>
40//
41//===----------------------------------------------------------------------===//
42
43#include "Transforms.h"
44#include "Internals.h"
45#include "clang/AST/ASTContext.h"
46#include "clang/AST/Attr.h"
47#include "clang/AST/ParentMap.h"
48#include "clang/Analysis/DomainSpecific/CocoaConventions.h"
49#include "clang/Basic/SourceManager.h"
50#include "clang/Lex/Lexer.h"
51#include "clang/Sema/SemaDiagnostic.h"
52#include "llvm/ADT/SmallString.h"
53
54using namespace clang;
55using namespace arcmt;
56using namespace trans;
57
58namespace {
59
60class UnbridgedCastRewriter : public RecursiveASTVisitor<UnbridgedCastRewriter>{
61  MigrationPass &Pass;
62  IdentifierInfo *SelfII;
63  std::unique_ptr<ParentMap> StmtMap;
64  Decl *ParentD;
65  Stmt *Body;
66  mutable std::unique_ptr<ExprSet> Removables;
67
68public:
69  UnbridgedCastRewriter(MigrationPass &pass) : Pass(pass), ParentD(0), Body(0) {
70    SelfII = &Pass.Ctx.Idents.get("self");
71  }
72
73  void transformBody(Stmt *body, Decl *ParentD) {
74    this->ParentD = ParentD;
75    Body = body;
76    StmtMap.reset(new ParentMap(body));
77    TraverseStmt(body);
78  }
79
80  bool TraverseBlockDecl(BlockDecl *D) {
81    // ParentMap does not enter into a BlockDecl to record its stmts, so use a
82    // new UnbridgedCastRewriter to handle the block.
83    UnbridgedCastRewriter(Pass).transformBody(D->getBody(), D);
84    return true;
85  }
86
87  bool VisitCastExpr(CastExpr *E) {
88    if (E->getCastKind() != CK_CPointerToObjCPointerCast &&
89        E->getCastKind() != CK_BitCast &&
90        E->getCastKind() != CK_AnyPointerToBlockPointerCast)
91      return true;
92
93    QualType castType = E->getType();
94    Expr *castExpr = E->getSubExpr();
95    QualType castExprType = castExpr->getType();
96
97    if (castType->isObjCRetainableType() == castExprType->isObjCRetainableType())
98      return true;
99
100    bool exprRetainable = castExprType->isObjCIndirectLifetimeType();
101    bool castRetainable = castType->isObjCIndirectLifetimeType();
102    if (exprRetainable == castRetainable) return true;
103
104    if (castExpr->isNullPointerConstant(Pass.Ctx,
105                                        Expr::NPC_ValueDependentIsNull))
106      return true;
107
108    SourceLocation loc = castExpr->getExprLoc();
109    if (loc.isValid() && Pass.Ctx.getSourceManager().isInSystemHeader(loc))
110      return true;
111
112    if (castType->isObjCRetainableType())
113      transformNonObjCToObjCCast(E);
114    else
115      transformObjCToNonObjCCast(E);
116
117    return true;
118  }
119
120private:
121  void transformNonObjCToObjCCast(CastExpr *E) {
122    if (!E) return;
123
124    // Global vars are assumed that are cast as unretained.
125    if (isGlobalVar(E))
126      if (E->getSubExpr()->getType()->isPointerType()) {
127        castToObjCObject(E, /*retained=*/false);
128        return;
129      }
130
131    // If the cast is directly over the result of a Core Foundation function
132    // try to figure out whether it should be cast as retained or unretained.
133    Expr *inner = E->IgnoreParenCasts();
134    if (CallExpr *callE = dyn_cast<CallExpr>(inner)) {
135      if (FunctionDecl *FD = callE->getDirectCallee()) {
136        if (FD->hasAttr<CFReturnsRetainedAttr>()) {
137          castToObjCObject(E, /*retained=*/true);
138          return;
139        }
140        if (FD->hasAttr<CFReturnsNotRetainedAttr>()) {
141          castToObjCObject(E, /*retained=*/false);
142          return;
143        }
144        if (FD->isGlobal() &&
145            FD->getIdentifier() &&
146            ento::cocoa::isRefType(E->getSubExpr()->getType(), "CF",
147                                   FD->getIdentifier()->getName())) {
148          StringRef fname = FD->getIdentifier()->getName();
149          if (fname.endswith("Retain") ||
150              fname.find("Create") != StringRef::npos ||
151              fname.find("Copy") != StringRef::npos) {
152            // Do not migrate to couple of bridge transfer casts which
153            // cancel each other out. Leave it unchanged so error gets user
154            // attention instead.
155            if (FD->getName() == "CFRetain" &&
156                FD->getNumParams() == 1 &&
157                FD->getParent()->isTranslationUnit() &&
158                FD->isExternallyVisible()) {
159              Expr *Arg = callE->getArg(0);
160              if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Arg)) {
161                const Expr *sub = ICE->getSubExpr();
162                QualType T = sub->getType();
163                if (T->isObjCObjectPointerType())
164                  return;
165              }
166            }
167            castToObjCObject(E, /*retained=*/true);
168            return;
169          }
170
171          if (fname.find("Get") != StringRef::npos) {
172            castToObjCObject(E, /*retained=*/false);
173            return;
174          }
175        }
176      }
177    }
178
179    // If returning an ivar or a member of an ivar from a +0 method, use
180    // a __bridge cast.
181    Expr *base = inner->IgnoreParenImpCasts();
182    while (isa<MemberExpr>(base))
183      base = cast<MemberExpr>(base)->getBase()->IgnoreParenImpCasts();
184    if (isa<ObjCIvarRefExpr>(base) &&
185        isa<ReturnStmt>(StmtMap->getParentIgnoreParenCasts(E))) {
186      if (ObjCMethodDecl *method = dyn_cast_or_null<ObjCMethodDecl>(ParentD)) {
187        if (!method->hasAttr<NSReturnsRetainedAttr>()) {
188          castToObjCObject(E, /*retained=*/false);
189          return;
190        }
191      }
192    }
193  }
194
195  void castToObjCObject(CastExpr *E, bool retained) {
196    rewriteToBridgedCast(E, retained ? OBC_BridgeTransfer : OBC_Bridge);
197  }
198
199  void rewriteToBridgedCast(CastExpr *E, ObjCBridgeCastKind Kind) {
200    Transaction Trans(Pass.TA);
201    rewriteToBridgedCast(E, Kind, Trans);
202  }
203
204  void rewriteToBridgedCast(CastExpr *E, ObjCBridgeCastKind Kind,
205                            Transaction &Trans) {
206    TransformActions &TA = Pass.TA;
207
208    // We will remove the compiler diagnostic.
209    if (!TA.hasDiagnostic(diag::err_arc_mismatched_cast,
210                          diag::err_arc_cast_requires_bridge,
211                          E->getLocStart())) {
212      Trans.abort();
213      return;
214    }
215
216    StringRef bridge;
217    switch(Kind) {
218    case OBC_Bridge:
219      bridge = "__bridge "; break;
220    case OBC_BridgeTransfer:
221      bridge = "__bridge_transfer "; break;
222    case OBC_BridgeRetained:
223      bridge = "__bridge_retained "; break;
224    }
225
226    TA.clearDiagnostic(diag::err_arc_mismatched_cast,
227                       diag::err_arc_cast_requires_bridge,
228                       E->getLocStart());
229    if (Kind == OBC_Bridge || !Pass.CFBridgingFunctionsDefined()) {
230      if (CStyleCastExpr *CCE = dyn_cast<CStyleCastExpr>(E)) {
231        TA.insertAfterToken(CCE->getLParenLoc(), bridge);
232      } else {
233        SourceLocation insertLoc = E->getSubExpr()->getLocStart();
234        SmallString<128> newCast;
235        newCast += '(';
236        newCast += bridge;
237        newCast += E->getType().getAsString(Pass.Ctx.getPrintingPolicy());
238        newCast += ')';
239
240        if (isa<ParenExpr>(E->getSubExpr())) {
241          TA.insert(insertLoc, newCast.str());
242        } else {
243          newCast += '(';
244          TA.insert(insertLoc, newCast.str());
245          TA.insertAfterToken(E->getLocEnd(), ")");
246        }
247      }
248    } else {
249      assert(Kind == OBC_BridgeTransfer || Kind == OBC_BridgeRetained);
250      SmallString<32> BridgeCall;
251
252      Expr *WrapE = E->getSubExpr();
253      SourceLocation InsertLoc = WrapE->getLocStart();
254
255      SourceManager &SM = Pass.Ctx.getSourceManager();
256      char PrevChar = *SM.getCharacterData(InsertLoc.getLocWithOffset(-1));
257      if (Lexer::isIdentifierBodyChar(PrevChar, Pass.Ctx.getLangOpts()))
258        BridgeCall += ' ';
259
260      if (Kind == OBC_BridgeTransfer)
261        BridgeCall += "CFBridgingRelease";
262      else
263        BridgeCall += "CFBridgingRetain";
264
265      if (isa<ParenExpr>(WrapE)) {
266        TA.insert(InsertLoc, BridgeCall);
267      } else {
268        BridgeCall += '(';
269        TA.insert(InsertLoc, BridgeCall);
270        TA.insertAfterToken(WrapE->getLocEnd(), ")");
271      }
272    }
273  }
274
275  void rewriteCastForCFRetain(CastExpr *castE, CallExpr *callE) {
276    Transaction Trans(Pass.TA);
277    Pass.TA.replace(callE->getSourceRange(), callE->getArg(0)->getSourceRange());
278    rewriteToBridgedCast(castE, OBC_BridgeRetained, Trans);
279  }
280
281  void getBlockMacroRanges(CastExpr *E, SourceRange &Outer, SourceRange &Inner) {
282    SourceManager &SM = Pass.Ctx.getSourceManager();
283    SourceLocation Loc = E->getExprLoc();
284    assert(Loc.isMacroID());
285    SourceLocation MacroBegin, MacroEnd;
286    std::tie(MacroBegin, MacroEnd) = SM.getImmediateExpansionRange(Loc);
287    SourceRange SubRange = E->getSubExpr()->IgnoreParenImpCasts()->getSourceRange();
288    SourceLocation InnerBegin = SM.getImmediateMacroCallerLoc(SubRange.getBegin());
289    SourceLocation InnerEnd = SM.getImmediateMacroCallerLoc(SubRange.getEnd());
290
291    Outer = SourceRange(MacroBegin, MacroEnd);
292    Inner = SourceRange(InnerBegin, InnerEnd);
293  }
294
295  void rewriteBlockCopyMacro(CastExpr *E) {
296    SourceRange OuterRange, InnerRange;
297    getBlockMacroRanges(E, OuterRange, InnerRange);
298
299    Transaction Trans(Pass.TA);
300    Pass.TA.replace(OuterRange, InnerRange);
301    Pass.TA.insert(InnerRange.getBegin(), "[");
302    Pass.TA.insertAfterToken(InnerRange.getEnd(), " copy]");
303    Pass.TA.clearDiagnostic(diag::err_arc_mismatched_cast,
304                            diag::err_arc_cast_requires_bridge,
305                            OuterRange);
306  }
307
308  void removeBlockReleaseMacro(CastExpr *E) {
309    SourceRange OuterRange, InnerRange;
310    getBlockMacroRanges(E, OuterRange, InnerRange);
311
312    Transaction Trans(Pass.TA);
313    Pass.TA.clearDiagnostic(diag::err_arc_mismatched_cast,
314                            diag::err_arc_cast_requires_bridge,
315                            OuterRange);
316    if (!hasSideEffects(E, Pass.Ctx)) {
317      if (tryRemoving(cast<Expr>(StmtMap->getParentIgnoreParenCasts(E))))
318        return;
319    }
320    Pass.TA.replace(OuterRange, InnerRange);
321  }
322
323  bool tryRemoving(Expr *E) const {
324    if (!Removables) {
325      Removables.reset(new ExprSet);
326      collectRemovables(Body, *Removables);
327    }
328
329    if (Removables->count(E)) {
330      Pass.TA.removeStmt(E);
331      return true;
332    }
333
334    return false;
335  }
336
337  void transformObjCToNonObjCCast(CastExpr *E) {
338    SourceLocation CastLoc = E->getExprLoc();
339    if (CastLoc.isMacroID()) {
340      StringRef MacroName = Lexer::getImmediateMacroName(CastLoc,
341                                                    Pass.Ctx.getSourceManager(),
342                                                    Pass.Ctx.getLangOpts());
343      if (MacroName == "Block_copy") {
344        rewriteBlockCopyMacro(E);
345        return;
346      }
347      if (MacroName == "Block_release") {
348        removeBlockReleaseMacro(E);
349        return;
350      }
351    }
352
353    if (isSelf(E->getSubExpr()))
354      return rewriteToBridgedCast(E, OBC_Bridge);
355
356    CallExpr *callE;
357    if (isPassedToCFRetain(E, callE))
358      return rewriteCastForCFRetain(E, callE);
359
360    ObjCMethodFamily family = getFamilyOfMessage(E->getSubExpr());
361    if (family == OMF_retain)
362      return rewriteToBridgedCast(E, OBC_BridgeRetained);
363
364    if (family == OMF_autorelease || family == OMF_release) {
365      std::string err = "it is not safe to cast to '";
366      err += E->getType().getAsString(Pass.Ctx.getPrintingPolicy());
367      err += "' the result of '";
368      err += family == OMF_autorelease ? "autorelease" : "release";
369      err += "' message; a __bridge cast may result in a pointer to a "
370          "destroyed object and a __bridge_retained may leak the object";
371      Pass.TA.reportError(err, E->getLocStart(),
372                          E->getSubExpr()->getSourceRange());
373      Stmt *parent = E;
374      do {
375        parent = StmtMap->getParentIgnoreParenImpCasts(parent);
376      } while (parent && isa<ExprWithCleanups>(parent));
377
378      if (ReturnStmt *retS = dyn_cast_or_null<ReturnStmt>(parent)) {
379        std::string note = "remove the cast and change return type of function "
380            "to '";
381        note += E->getSubExpr()->getType().getAsString(Pass.Ctx.getPrintingPolicy());
382        note += "' to have the object automatically autoreleased";
383        Pass.TA.reportNote(note, retS->getLocStart());
384      }
385    }
386
387    Expr *subExpr = E->getSubExpr();
388
389    // Look through pseudo-object expressions.
390    if (PseudoObjectExpr *pseudo = dyn_cast<PseudoObjectExpr>(subExpr)) {
391      subExpr = pseudo->getResultExpr();
392      assert(subExpr && "no result for pseudo-object of non-void type?");
393    }
394
395    if (ImplicitCastExpr *implCE = dyn_cast<ImplicitCastExpr>(subExpr)) {
396      if (implCE->getCastKind() == CK_ARCConsumeObject)
397        return rewriteToBridgedCast(E, OBC_BridgeRetained);
398      if (implCE->getCastKind() == CK_ARCReclaimReturnedObject)
399        return rewriteToBridgedCast(E, OBC_Bridge);
400    }
401
402    bool isConsumed = false;
403    if (isPassedToCParamWithKnownOwnership(E, isConsumed))
404      return rewriteToBridgedCast(E, isConsumed ? OBC_BridgeRetained
405                                                : OBC_Bridge);
406  }
407
408  static ObjCMethodFamily getFamilyOfMessage(Expr *E) {
409    E = E->IgnoreParenCasts();
410    if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E))
411      return ME->getMethodFamily();
412
413    return OMF_None;
414  }
415
416  bool isPassedToCFRetain(Expr *E, CallExpr *&callE) const {
417    if ((callE = dyn_cast_or_null<CallExpr>(
418                                     StmtMap->getParentIgnoreParenImpCasts(E))))
419      if (FunctionDecl *
420            FD = dyn_cast_or_null<FunctionDecl>(callE->getCalleeDecl()))
421        if (FD->getName() == "CFRetain" && FD->getNumParams() == 1 &&
422            FD->getParent()->isTranslationUnit() &&
423            FD->isExternallyVisible())
424          return true;
425
426    return false;
427  }
428
429  bool isPassedToCParamWithKnownOwnership(Expr *E, bool &isConsumed) const {
430    if (CallExpr *callE = dyn_cast_or_null<CallExpr>(
431                                     StmtMap->getParentIgnoreParenImpCasts(E)))
432      if (FunctionDecl *
433            FD = dyn_cast_or_null<FunctionDecl>(callE->getCalleeDecl())) {
434        unsigned i = 0;
435        for (unsigned e = callE->getNumArgs(); i != e; ++i) {
436          Expr *arg = callE->getArg(i);
437          if (arg == E || arg->IgnoreParenImpCasts() == E)
438            break;
439        }
440        if (i < callE->getNumArgs() && i < FD->getNumParams()) {
441          ParmVarDecl *PD = FD->getParamDecl(i);
442          if (PD->hasAttr<CFConsumedAttr>()) {
443            isConsumed = true;
444            return true;
445          }
446        }
447      }
448
449    return false;
450  }
451
452  bool isSelf(Expr *E) const {
453    E = E->IgnoreParenLValueCasts();
454    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
455      if (ImplicitParamDecl *IPD = dyn_cast<ImplicitParamDecl>(DRE->getDecl()))
456        if (IPD->getIdentifier() == SelfII)
457          return true;
458
459    return false;
460  }
461};
462
463} // end anonymous namespace
464
465void trans::rewriteUnbridgedCasts(MigrationPass &pass) {
466  BodyTransform<UnbridgedCastRewriter> trans(pass);
467  trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
468}
469