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
53using namespace clang;
54using namespace arcmt;
55using namespace trans;
56
57namespace {
58
59class 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
67public:
68 UnbridgedCastRewriter(MigrationPass &pass)
69 : Pass(pass), ParentD(nullptr), Body(nullptr) {
70 SelfII = &Pass.Ctx.Idents.get(Name: "self");
71 }
72
73 void transformBody(Stmt *body, Decl *ParentD) {
74 this->ParentD = ParentD;
75 Body = body;
76 StmtMap.reset(p: new ParentMap(body));
77 TraverseStmt(S: 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(Ctx&: Pass.Ctx,
105 NPC: Expr::NPC_ValueDependentIsNull))
106 return true;
107
108 SourceLocation loc = castExpr->getExprLoc();
109 if (loc.isValid() && Pass.Ctx.getSourceManager().isInSystemHeader(Loc: 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>(Val: 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(RetTy: E->getSubExpr()->getType(), Prefix: "CF",
147 Name: FD->getIdentifier()->getName())) {
148 StringRef fname = FD->getIdentifier()->getName();
149 if (fname.ends_with(Suffix: "Retain") || fname.contains(Other: "Create") ||
150 fname.contains(Other: "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(Arg: 0);
159 if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Val: 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(Other: "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>(Val: base))
182 base = cast<MemberExpr>(Val: base)->getBase()->IgnoreParenImpCasts();
183 if (isa<ObjCIvarRefExpr>(Val: base) &&
184 isa<ReturnStmt>(StmtMap->getParentIgnoreParenCasts(E))) {
185 if (ObjCMethodDecl *method = dyn_cast_or_null<ObjCMethodDecl>(Val: ParentD)) {
186 if (!method->hasAttr<NSReturnsRetainedAttr>()) {
187 castToObjCObject(E, /*retained=*/false);
188 return;
189 }
190 }
191 }
192 }
193
194 void castToObjCObject(CastExpr *E, bool retained) {
195 rewriteToBridgedCast(E, Kind: retained ? OBC_BridgeTransfer : OBC_Bridge);
196 }
197
198 void rewriteToBridgedCast(CastExpr *E, ObjCBridgeCastKind Kind) {
199 Transaction Trans(Pass.TA);
200 rewriteToBridgedCast(E, Kind, Trans);
201 }
202
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>(Val: E)) {
229 TA.insertAfterToken(loc: CCE->getLParenLoc(), text: 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>(Val: E->getSubExpr())) {
239 TA.insert(loc: insertLoc, text: newCast.str());
240 } else {
241 newCast += '(';
242 TA.insert(loc: insertLoc, text: newCast.str());
243 TA.insertAfterToken(loc: E->getEndLoc(), text: ")");
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(SL: InsertLoc.getLocWithOffset(Offset: -1));
255 if (Lexer::isAsciiIdentifierContinueChar(c: PrevChar,
256 LangOpts: Pass.Ctx.getLangOpts()))
257 BridgeCall += ' ';
258
259 if (Kind == OBC_BridgeTransfer)
260 BridgeCall += "CFBridgingRelease";
261 else
262 BridgeCall += "CFBridgingRetain";
263
264 if (isa<ParenExpr>(Val: WrapE)) {
265 TA.insert(loc: InsertLoc, text: BridgeCall);
266 } else {
267 BridgeCall += '(';
268 TA.insert(loc: InsertLoc, text: BridgeCall);
269 TA.insertAfterToken(loc: WrapE->getEndLoc(), text: ")");
270 }
271 }
272 }
273
274 void rewriteCastForCFRetain(CastExpr *castE, CallExpr *callE) {
275 Transaction Trans(Pass.TA);
276 Pass.TA.replace(callE->getSourceRange(), callE->getArg(Arg: 0)->getSourceRange());
277 rewriteToBridgedCast(E: castE, Kind: OBC_BridgeRetained, Trans);
278 }
279
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(Loc: SubRange.getBegin());
287 SourceLocation InnerEnd = SM.getImmediateMacroCallerLoc(Loc: SubRange.getEnd());
288
289 Outer = MacroRange.getAsRange();
290 Inner = SourceRange(InnerBegin, InnerEnd);
291 }
292
293 void rewriteBlockCopyMacro(CastExpr *E) {
294 SourceRange OuterRange, InnerRange;
295 getBlockMacroRanges(E, Outer&: OuterRange, Inner&: InnerRange);
296
297 Transaction Trans(Pass.TA);
298 Pass.TA.replace(range: OuterRange, replacementRange: InnerRange);
299 Pass.TA.insert(loc: InnerRange.getBegin(), text: "[");
300 Pass.TA.insertAfterToken(loc: InnerRange.getEnd(), text: " copy]");
301 Pass.TA.clearDiagnostic(diag::err_arc_mismatched_cast,
302 diag::err_arc_cast_requires_bridge,
303 OuterRange);
304 }
305
306 void removeBlockReleaseMacro(CastExpr *E) {
307 SourceRange OuterRange, InnerRange;
308 getBlockMacroRanges(E, Outer&: OuterRange, Inner&: 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(E: cast<Expr>(StmtMap->getParentIgnoreParenCasts(E))))
316 return;
317 }
318 Pass.TA.replace(range: OuterRange, replacementRange: InnerRange);
319 }
320
321 bool tryRemoving(Expr *E) const {
322 if (!Removables) {
323 Removables.reset(p: new ExprSet);
324 collectRemovables(S: Body, exprs&: *Removables);
325 }
326
327 if (Removables->count(V: E)) {
328 Pass.TA.removeStmt(E);
329 return true;
330 }
331
332 return false;
333 }
334
335 void transformObjCToNonObjCCast(CastExpr *E) {
336 SourceLocation CastLoc = E->getExprLoc();
337 if (CastLoc.isMacroID()) {
338 StringRef MacroName = Lexer::getImmediateMacroName(Loc: CastLoc,
339 SM: Pass.Ctx.getSourceManager(),
340 LangOpts: 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: E->getSubExpr()))
352 return rewriteToBridgedCast(E, Kind: OBC_Bridge);
353
354 CallExpr *callE;
355 if (isPassedToCFRetain(E, callE))
356 return rewriteCastForCFRetain(castE: E, callE);
357
358 ObjCMethodFamily family = getFamilyOfMessage(E: E->getSubExpr());
359 if (family == OMF_retain)
360 return rewriteToBridgedCast(E, Kind: 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(error: err, loc: E->getBeginLoc(),
370 range: E->getSubExpr()->getSourceRange());
371 Stmt *parent = E;
372 do {
373 parent = StmtMap->getParentIgnoreParenImpCasts(parent);
374 } while (parent && isa<FullExpr>(Val: parent));
375
376 if (ReturnStmt *retS = dyn_cast_or_null<ReturnStmt>(Val: parent)) {
377 std::string note = "remove the cast and change return type of function "
378 "to '";
379 note += E->getSubExpr()->getType().getAsString(Policy: Pass.Ctx.getPrintingPolicy());
380 note += "' to have the object automatically autoreleased";
381 Pass.TA.reportNote(note, loc: retS->getBeginLoc());
382 }
383 }
384
385 Expr *subExpr = E->getSubExpr();
386
387 // Look through pseudo-object expressions.
388 if (PseudoObjectExpr *pseudo = dyn_cast<PseudoObjectExpr>(Val: 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>(Val: subExpr)) {
394 if (implCE->getCastKind() == CK_ARCConsumeObject)
395 return rewriteToBridgedCast(E, Kind: OBC_BridgeRetained);
396 if (implCE->getCastKind() == CK_ARCReclaimReturnedObject)
397 return rewriteToBridgedCast(E, Kind: OBC_Bridge);
398 }
399
400 bool isConsumed = false;
401 if (isPassedToCParamWithKnownOwnership(E, isConsumed))
402 return rewriteToBridgedCast(E, Kind: isConsumed ? OBC_BridgeRetained
403 : OBC_Bridge);
404 }
405
406 static ObjCMethodFamily getFamilyOfMessage(Expr *E) {
407 E = E->IgnoreParenCasts();
408 if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(Val: E))
409 return ME->getMethodFamily();
410
411 return OMF_None;
412 }
413
414 bool isPassedToCFRetain(Expr *E, CallExpr *&callE) const {
415 if ((callE = dyn_cast_or_null<CallExpr>(
416 Val: StmtMap->getParentIgnoreParenImpCasts(E))))
417 if (FunctionDecl *
418 FD = dyn_cast_or_null<FunctionDecl>(Val: 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
427 bool isPassedToCParamWithKnownOwnership(Expr *E, bool &isConsumed) const {
428 if (CallExpr *callE = dyn_cast_or_null<CallExpr>(
429 Val: StmtMap->getParentIgnoreParenImpCasts(E)))
430 if (FunctionDecl *
431 FD = dyn_cast_or_null<FunctionDecl>(Val: callE->getCalleeDecl())) {
432 unsigned i = 0;
433 for (unsigned e = callE->getNumArgs(); i != e; ++i) {
434 Expr *arg = callE->getArg(Arg: 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
450 bool isSelf(Expr *E) const {
451 E = E->IgnoreParenLValueCasts();
452 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Val: E))
453 if (ImplicitParamDecl *IPD = dyn_cast<ImplicitParamDecl>(Val: DRE->getDecl()))
454 if (IPD->getIdentifier() == SelfII)
455 return true;
456
457 return false;
458 }
459};
460
461} // end anonymous namespace
462
463void trans::rewriteUnbridgedCasts(MigrationPass &pass) {
464 BodyTransform<UnbridgedCastRewriter> trans(pass);
465 trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
466}
467

source code of clang/lib/ARCMigrate/TransUnbridgedCasts.cpp