1 //===--- TransUnbridgedCasts.cpp - Transformations to ARC mode ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // rewriteUnbridgedCasts:
10 //
11 // A cast of non-objc pointer to an objc one is checked. If the non-objc pointer
12 // is from a file-level variable, __bridge cast is used to convert it.
13 // For the result of a function call that we know is +1/+0,
14 // __bridge/CFBridgingRelease is used.
15 //
16 // NSString *str = (NSString *)kUTTypePlainText;
17 // str = b ? kUTTypeRTF : kUTTypePlainText;
18 // NSString *_uuidString = (NSString *)CFUUIDCreateString(kCFAllocatorDefault,
19 // _uuid);
20 // ---->
21 // NSString *str = (__bridge NSString *)kUTTypePlainText;
22 // str = (__bridge NSString *)(b ? kUTTypeRTF : kUTTypePlainText);
23 // NSString *_uuidString = (NSString *)
24 // CFBridgingRelease(CFUUIDCreateString(kCFAllocatorDefault, _uuid));
25 //
26 // For a C pointer to ObjC, for casting 'self', __bridge is used.
27 //
28 // CFStringRef str = (CFStringRef)self;
29 // ---->
30 // CFStringRef str = (__bridge CFStringRef)self;
31 //
32 // Uses of Block_copy/Block_release macros are rewritten:
33 //
34 // c = Block_copy(b);
35 // Block_release(c);
36 // ---->
37 // c = [b copy];
38 // <removed>
39 //
40 //===----------------------------------------------------------------------===//
41
42 #include "Transforms.h"
43 #include "Internals.h"
44 #include "clang/AST/ASTContext.h"
45 #include "clang/AST/Attr.h"
46 #include "clang/AST/ParentMap.h"
47 #include "clang/Analysis/DomainSpecific/CocoaConventions.h"
48 #include "clang/Basic/SourceManager.h"
49 #include "clang/Lex/Lexer.h"
50 #include "clang/Sema/SemaDiagnostic.h"
51 #include "llvm/ADT/SmallString.h"
52
53 using namespace clang;
54 using namespace arcmt;
55 using namespace trans;
56
57 namespace {
58
59 class UnbridgedCastRewriter : public RecursiveASTVisitor<UnbridgedCastRewriter>{
60 MigrationPass &Pass;
61 IdentifierInfo *SelfII;
62 std::unique_ptr<ParentMap> StmtMap;
63 Decl *ParentD;
64 Stmt *Body;
65 mutable std::unique_ptr<ExprSet> Removables;
66
67 public:
UnbridgedCastRewriter(MigrationPass & pass)68 UnbridgedCastRewriter(MigrationPass &pass)
69 : Pass(pass), ParentD(nullptr), Body(nullptr) {
70 SelfII = &Pass.Ctx.Idents.get("self");
71 }
72
transformBody(Stmt * body,Decl * ParentD)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
TraverseBlockDecl(BlockDecl * D)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
VisitCastExpr(CastExpr * E)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
120 private:
transformNonObjCToObjCCast(CastExpr * E)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.ends_with("Retain") || fname.contains("Create") ||
150 fname.contains("Copy")) {
151 // Do not migrate to couple of bridge transfer casts which
152 // cancel each other out. Leave it unchanged so error gets user
153 // attention instead.
154 if (FD->getName() == "CFRetain" &&
155 FD->getNumParams() == 1 &&
156 FD->getParent()->isTranslationUnit() &&
157 FD->isExternallyVisible()) {
158 Expr *Arg = callE->getArg(0);
159 if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Arg)) {
160 const Expr *sub = ICE->getSubExpr();
161 QualType T = sub->getType();
162 if (T->isObjCObjectPointerType())
163 return;
164 }
165 }
166 castToObjCObject(E, /*retained=*/true);
167 return;
168 }
169
170 if (fname.contains("Get")) {
171 castToObjCObject(E, /*retained=*/false);
172 return;
173 }
174 }
175 }
176 }
177
178 // If returning an ivar or a member of an ivar from a +0 method, use
179 // a __bridge cast.
180 Expr *base = inner->IgnoreParenImpCasts();
181 while (isa<MemberExpr>(base))
182 base = cast<MemberExpr>(base)->getBase()->IgnoreParenImpCasts();
183 if (isa<ObjCIvarRefExpr>(base) &&
184 isa<ReturnStmt>(StmtMap->getParentIgnoreParenCasts(E))) {
185 if (ObjCMethodDecl *method = dyn_cast_or_null<ObjCMethodDecl>(ParentD)) {
186 if (!method->hasAttr<NSReturnsRetainedAttr>()) {
187 castToObjCObject(E, /*retained=*/false);
188 return;
189 }
190 }
191 }
192 }
193
castToObjCObject(CastExpr * E,bool retained)194 void castToObjCObject(CastExpr *E, bool retained) {
195 rewriteToBridgedCast(E, retained ? OBC_BridgeTransfer : OBC_Bridge);
196 }
197
rewriteToBridgedCast(CastExpr * E,ObjCBridgeCastKind Kind)198 void rewriteToBridgedCast(CastExpr *E, ObjCBridgeCastKind Kind) {
199 Transaction Trans(Pass.TA);
200 rewriteToBridgedCast(E, Kind, Trans);
201 }
202
rewriteToBridgedCast(CastExpr * E,ObjCBridgeCastKind Kind,Transaction & Trans)203 void rewriteToBridgedCast(CastExpr *E, ObjCBridgeCastKind Kind,
204 Transaction &Trans) {
205 TransformActions &TA = Pass.TA;
206
207 // We will remove the compiler diagnostic.
208 if (!TA.hasDiagnostic(diag::err_arc_mismatched_cast,
209 diag::err_arc_cast_requires_bridge,
210 E->getBeginLoc())) {
211 Trans.abort();
212 return;
213 }
214
215 StringRef bridge;
216 switch(Kind) {
217 case OBC_Bridge:
218 bridge = "__bridge "; break;
219 case OBC_BridgeTransfer:
220 bridge = "__bridge_transfer "; break;
221 case OBC_BridgeRetained:
222 bridge = "__bridge_retained "; break;
223 }
224
225 TA.clearDiagnostic(diag::err_arc_mismatched_cast,
226 diag::err_arc_cast_requires_bridge, E->getBeginLoc());
227 if (Kind == OBC_Bridge || !Pass.CFBridgingFunctionsDefined()) {
228 if (CStyleCastExpr *CCE = dyn_cast<CStyleCastExpr>(E)) {
229 TA.insertAfterToken(CCE->getLParenLoc(), bridge);
230 } else {
231 SourceLocation insertLoc = E->getSubExpr()->getBeginLoc();
232 SmallString<128> newCast;
233 newCast += '(';
234 newCast += bridge;
235 newCast += E->getType().getAsString(Pass.Ctx.getPrintingPolicy());
236 newCast += ')';
237
238 if (isa<ParenExpr>(E->getSubExpr())) {
239 TA.insert(insertLoc, newCast.str());
240 } else {
241 newCast += '(';
242 TA.insert(insertLoc, newCast.str());
243 TA.insertAfterToken(E->getEndLoc(), ")");
244 }
245 }
246 } else {
247 assert(Kind == OBC_BridgeTransfer || Kind == OBC_BridgeRetained);
248 SmallString<32> BridgeCall;
249
250 Expr *WrapE = E->getSubExpr();
251 SourceLocation InsertLoc = WrapE->getBeginLoc();
252
253 SourceManager &SM = Pass.Ctx.getSourceManager();
254 char PrevChar = *SM.getCharacterData(InsertLoc.getLocWithOffset(-1));
255 if (Lexer::isAsciiIdentifierContinueChar(PrevChar,
256 Pass.Ctx.getLangOpts()))
257 BridgeCall += ' ';
258
259 if (Kind == OBC_BridgeTransfer)
260 BridgeCall += "CFBridgingRelease";
261 else
262 BridgeCall += "CFBridgingRetain";
263
264 if (isa<ParenExpr>(WrapE)) {
265 TA.insert(InsertLoc, BridgeCall);
266 } else {
267 BridgeCall += '(';
268 TA.insert(InsertLoc, BridgeCall);
269 TA.insertAfterToken(WrapE->getEndLoc(), ")");
270 }
271 }
272 }
273
rewriteCastForCFRetain(CastExpr * castE,CallExpr * callE)274 void rewriteCastForCFRetain(CastExpr *castE, CallExpr *callE) {
275 Transaction Trans(Pass.TA);
276 Pass.TA.replace(callE->getSourceRange(), callE->getArg(0)->getSourceRange());
277 rewriteToBridgedCast(castE, OBC_BridgeRetained, Trans);
278 }
279
getBlockMacroRanges(CastExpr * E,SourceRange & Outer,SourceRange & Inner)280 void getBlockMacroRanges(CastExpr *E, SourceRange &Outer, SourceRange &Inner) {
281 SourceManager &SM = Pass.Ctx.getSourceManager();
282 SourceLocation Loc = E->getExprLoc();
283 assert(Loc.isMacroID());
284 CharSourceRange MacroRange = SM.getImmediateExpansionRange(Loc);
285 SourceRange SubRange = E->getSubExpr()->IgnoreParenImpCasts()->getSourceRange();
286 SourceLocation InnerBegin = SM.getImmediateMacroCallerLoc(SubRange.getBegin());
287 SourceLocation InnerEnd = SM.getImmediateMacroCallerLoc(SubRange.getEnd());
288
289 Outer = MacroRange.getAsRange();
290 Inner = SourceRange(InnerBegin, InnerEnd);
291 }
292
rewriteBlockCopyMacro(CastExpr * E)293 void rewriteBlockCopyMacro(CastExpr *E) {
294 SourceRange OuterRange, InnerRange;
295 getBlockMacroRanges(E, OuterRange, InnerRange);
296
297 Transaction Trans(Pass.TA);
298 Pass.TA.replace(OuterRange, InnerRange);
299 Pass.TA.insert(InnerRange.getBegin(), "[");
300 Pass.TA.insertAfterToken(InnerRange.getEnd(), " copy]");
301 Pass.TA.clearDiagnostic(diag::err_arc_mismatched_cast,
302 diag::err_arc_cast_requires_bridge,
303 OuterRange);
304 }
305
removeBlockReleaseMacro(CastExpr * E)306 void removeBlockReleaseMacro(CastExpr *E) {
307 SourceRange OuterRange, InnerRange;
308 getBlockMacroRanges(E, OuterRange, InnerRange);
309
310 Transaction Trans(Pass.TA);
311 Pass.TA.clearDiagnostic(diag::err_arc_mismatched_cast,
312 diag::err_arc_cast_requires_bridge,
313 OuterRange);
314 if (!hasSideEffects(E, Pass.Ctx)) {
315 if (tryRemoving(cast<Expr>(StmtMap->getParentIgnoreParenCasts(E))))
316 return;
317 }
318 Pass.TA.replace(OuterRange, InnerRange);
319 }
320
tryRemoving(Expr * E) const321 bool tryRemoving(Expr *E) const {
322 if (!Removables) {
323 Removables.reset(new ExprSet);
324 collectRemovables(Body, *Removables);
325 }
326
327 if (Removables->count(E)) {
328 Pass.TA.removeStmt(E);
329 return true;
330 }
331
332 return false;
333 }
334
transformObjCToNonObjCCast(CastExpr * E)335 void transformObjCToNonObjCCast(CastExpr *E) {
336 SourceLocation CastLoc = E->getExprLoc();
337 if (CastLoc.isMacroID()) {
338 StringRef MacroName = Lexer::getImmediateMacroName(CastLoc,
339 Pass.Ctx.getSourceManager(),
340 Pass.Ctx.getLangOpts());
341 if (MacroName == "Block_copy") {
342 rewriteBlockCopyMacro(E);
343 return;
344 }
345 if (MacroName == "Block_release") {
346 removeBlockReleaseMacro(E);
347 return;
348 }
349 }
350
351 if (isSelf(E->getSubExpr()))
352 return rewriteToBridgedCast(E, OBC_Bridge);
353
354 CallExpr *callE;
355 if (isPassedToCFRetain(E, callE))
356 return rewriteCastForCFRetain(E, callE);
357
358 ObjCMethodFamily family = getFamilyOfMessage(E->getSubExpr());
359 if (family == OMF_retain)
360 return rewriteToBridgedCast(E, OBC_BridgeRetained);
361
362 if (family == OMF_autorelease || family == OMF_release) {
363 std::string err = "it is not safe to cast to '";
364 err += E->getType().getAsString(Pass.Ctx.getPrintingPolicy());
365 err += "' the result of '";
366 err += family == OMF_autorelease ? "autorelease" : "release";
367 err += "' message; a __bridge cast may result in a pointer to a "
368 "destroyed object and a __bridge_retained may leak the object";
369 Pass.TA.reportError(err, E->getBeginLoc(),
370 E->getSubExpr()->getSourceRange());
371 Stmt *parent = E;
372 do {
373 parent = StmtMap->getParentIgnoreParenImpCasts(parent);
374 } while (isa_and_nonnull<FullExpr>(parent));
375
376 if (ReturnStmt *retS = dyn_cast_or_null<ReturnStmt>(parent)) {
377 std::string note = "remove the cast and change return type of function "
378 "to '";
379 note += E->getSubExpr()->getType().getAsString(Pass.Ctx.getPrintingPolicy());
380 note += "' to have the object automatically autoreleased";
381 Pass.TA.reportNote(note, retS->getBeginLoc());
382 }
383 }
384
385 Expr *subExpr = E->getSubExpr();
386
387 // Look through pseudo-object expressions.
388 if (PseudoObjectExpr *pseudo = dyn_cast<PseudoObjectExpr>(subExpr)) {
389 subExpr = pseudo->getResultExpr();
390 assert(subExpr && "no result for pseudo-object of non-void type?");
391 }
392
393 if (ImplicitCastExpr *implCE = dyn_cast<ImplicitCastExpr>(subExpr)) {
394 if (implCE->getCastKind() == CK_ARCConsumeObject)
395 return rewriteToBridgedCast(E, OBC_BridgeRetained);
396 if (implCE->getCastKind() == CK_ARCReclaimReturnedObject)
397 return rewriteToBridgedCast(E, OBC_Bridge);
398 }
399
400 bool isConsumed = false;
401 if (isPassedToCParamWithKnownOwnership(E, isConsumed))
402 return rewriteToBridgedCast(E, isConsumed ? OBC_BridgeRetained
403 : OBC_Bridge);
404 }
405
getFamilyOfMessage(Expr * E)406 static ObjCMethodFamily getFamilyOfMessage(Expr *E) {
407 E = E->IgnoreParenCasts();
408 if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E))
409 return ME->getMethodFamily();
410
411 return OMF_None;
412 }
413
isPassedToCFRetain(Expr * E,CallExpr * & callE) const414 bool isPassedToCFRetain(Expr *E, CallExpr *&callE) const {
415 if ((callE = dyn_cast_or_null<CallExpr>(
416 StmtMap->getParentIgnoreParenImpCasts(E))))
417 if (FunctionDecl *
418 FD = dyn_cast_or_null<FunctionDecl>(callE->getCalleeDecl()))
419 if (FD->getName() == "CFRetain" && FD->getNumParams() == 1 &&
420 FD->getParent()->isTranslationUnit() &&
421 FD->isExternallyVisible())
422 return true;
423
424 return false;
425 }
426
isPassedToCParamWithKnownOwnership(Expr * E,bool & isConsumed) const427 bool isPassedToCParamWithKnownOwnership(Expr *E, bool &isConsumed) const {
428 if (CallExpr *callE = dyn_cast_or_null<CallExpr>(
429 StmtMap->getParentIgnoreParenImpCasts(E)))
430 if (FunctionDecl *
431 FD = dyn_cast_or_null<FunctionDecl>(callE->getCalleeDecl())) {
432 unsigned i = 0;
433 for (unsigned e = callE->getNumArgs(); i != e; ++i) {
434 Expr *arg = callE->getArg(i);
435 if (arg == E || arg->IgnoreParenImpCasts() == E)
436 break;
437 }
438 if (i < callE->getNumArgs() && i < FD->getNumParams()) {
439 ParmVarDecl *PD = FD->getParamDecl(i);
440 if (PD->hasAttr<CFConsumedAttr>()) {
441 isConsumed = true;
442 return true;
443 }
444 }
445 }
446
447 return false;
448 }
449
isSelf(Expr * E) const450 bool isSelf(Expr *E) const {
451 E = E->IgnoreParenLValueCasts();
452 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
453 if (ImplicitParamDecl *IPD = dyn_cast<ImplicitParamDecl>(DRE->getDecl()))
454 if (IPD->getIdentifier() == SelfII)
455 return true;
456
457 return false;
458 }
459 };
460
461 } // end anonymous namespace
462
rewriteUnbridgedCasts(MigrationPass & pass)463 void trans::rewriteUnbridgedCasts(MigrationPass &pass) {
464 BodyTransform<UnbridgedCastRewriter> trans(pass);
465 trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
466 }
467