1 //==- CheckObjCDealloc.cpp - Check ObjC -dealloc implementation --*- C++ -*-==//
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 // This file defines a CheckObjCDealloc, a checker that
11 // analyzes an Objective-C class's implementation to determine if it
12 // correctly implements -dealloc.
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "ClangSACheckers.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
20 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
21 #include "clang/AST/ExprObjC.h"
22 #include "clang/AST/Expr.h"
23 #include "clang/AST/DeclObjC.h"
24 #include "clang/Basic/LangOptions.h"
25 #include "llvm/Support/raw_ostream.h"
26
27 using namespace clang;
28 using namespace ento;
29
scan_dealloc(Stmt * S,Selector Dealloc)30 static bool scan_dealloc(Stmt* S, Selector Dealloc) {
31
32 if (ObjCMessageExpr* ME = dyn_cast<ObjCMessageExpr>(S))
33 if (ME->getSelector() == Dealloc) {
34 switch (ME->getReceiverKind()) {
35 case ObjCMessageExpr::Instance: return false;
36 case ObjCMessageExpr::SuperInstance: return true;
37 case ObjCMessageExpr::Class: break;
38 case ObjCMessageExpr::SuperClass: break;
39 }
40 }
41
42 // Recurse to children.
43
44 for (Stmt::child_iterator I = S->child_begin(), E= S->child_end(); I!=E; ++I)
45 if (*I && scan_dealloc(*I, Dealloc))
46 return true;
47
48 return false;
49 }
50
scan_ivar_release(Stmt * S,ObjCIvarDecl * ID,const ObjCPropertyDecl * PD,Selector Release,IdentifierInfo * SelfII,ASTContext & Ctx)51 static bool scan_ivar_release(Stmt* S, ObjCIvarDecl* ID,
52 const ObjCPropertyDecl* PD,
53 Selector Release,
54 IdentifierInfo* SelfII,
55 ASTContext& Ctx) {
56
57 // [mMyIvar release]
58 if (ObjCMessageExpr* ME = dyn_cast<ObjCMessageExpr>(S))
59 if (ME->getSelector() == Release)
60 if (ME->getInstanceReceiver())
61 if (Expr* Receiver = ME->getInstanceReceiver()->IgnoreParenCasts())
62 if (ObjCIvarRefExpr* E = dyn_cast<ObjCIvarRefExpr>(Receiver))
63 if (E->getDecl() == ID)
64 return true;
65
66 // [self setMyIvar:nil];
67 if (ObjCMessageExpr* ME = dyn_cast<ObjCMessageExpr>(S))
68 if (ME->getInstanceReceiver())
69 if (Expr* Receiver = ME->getInstanceReceiver()->IgnoreParenCasts())
70 if (DeclRefExpr* E = dyn_cast<DeclRefExpr>(Receiver))
71 if (E->getDecl()->getIdentifier() == SelfII)
72 if (ME->getMethodDecl() == PD->getSetterMethodDecl() &&
73 ME->getNumArgs() == 1 &&
74 ME->getArg(0)->isNullPointerConstant(Ctx,
75 Expr::NPC_ValueDependentIsNull))
76 return true;
77
78 // self.myIvar = nil;
79 if (BinaryOperator* BO = dyn_cast<BinaryOperator>(S))
80 if (BO->isAssignmentOp())
81 if (ObjCPropertyRefExpr* PRE =
82 dyn_cast<ObjCPropertyRefExpr>(BO->getLHS()->IgnoreParenCasts()))
83 if (PRE->isExplicitProperty() && PRE->getExplicitProperty() == PD)
84 if (BO->getRHS()->isNullPointerConstant(Ctx,
85 Expr::NPC_ValueDependentIsNull)) {
86 // This is only a 'release' if the property kind is not
87 // 'assign'.
88 return PD->getSetterKind() != ObjCPropertyDecl::Assign;;
89 }
90
91 // Recurse to children.
92 for (Stmt::child_iterator I = S->child_begin(), E= S->child_end(); I!=E; ++I)
93 if (*I && scan_ivar_release(*I, ID, PD, Release, SelfII, Ctx))
94 return true;
95
96 return false;
97 }
98
checkObjCDealloc(const ObjCImplementationDecl * D,const LangOptions & LOpts,BugReporter & BR)99 static void checkObjCDealloc(const ObjCImplementationDecl* D,
100 const LangOptions& LOpts, BugReporter& BR) {
101
102 assert (LOpts.getGCMode() != LangOptions::GCOnly);
103
104 ASTContext& Ctx = BR.getContext();
105 const ObjCInterfaceDecl* ID = D->getClassInterface();
106
107 // Does the class contain any ivars that are pointers (or id<...>)?
108 // If not, skip the check entirely.
109 // NOTE: This is motivated by PR 2517:
110 // http://llvm.org/bugs/show_bug.cgi?id=2517
111
112 bool containsPointerIvar = false;
113
114 for (ObjCInterfaceDecl::ivar_iterator I=ID->ivar_begin(), E=ID->ivar_end();
115 I!=E; ++I) {
116
117 ObjCIvarDecl* ID = *I;
118 QualType T = ID->getType();
119
120 if (!T->isObjCObjectPointerType() ||
121 ID->getAttr<IBOutletAttr>() || // Skip IBOutlets.
122 ID->getAttr<IBOutletCollectionAttr>()) // Skip IBOutletCollections.
123 continue;
124
125 containsPointerIvar = true;
126 break;
127 }
128
129 if (!containsPointerIvar)
130 return;
131
132 // Determine if the class subclasses NSObject.
133 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
134 IdentifierInfo* SenTestCaseII = &Ctx.Idents.get("SenTestCase");
135
136
137 for ( ; ID ; ID = ID->getSuperClass()) {
138 IdentifierInfo *II = ID->getIdentifier();
139
140 if (II == NSObjectII)
141 break;
142
143 // FIXME: For now, ignore classes that subclass SenTestCase, as these don't
144 // need to implement -dealloc. They implement tear down in another way,
145 // which we should try and catch later.
146 // http://llvm.org/bugs/show_bug.cgi?id=3187
147 if (II == SenTestCaseII)
148 return;
149 }
150
151 if (!ID)
152 return;
153
154 // Get the "dealloc" selector.
155 IdentifierInfo* II = &Ctx.Idents.get("dealloc");
156 Selector S = Ctx.Selectors.getSelector(0, &II);
157 ObjCMethodDecl* MD = 0;
158
159 // Scan the instance methods for "dealloc".
160 for (ObjCImplementationDecl::instmeth_iterator I = D->instmeth_begin(),
161 E = D->instmeth_end(); I!=E; ++I) {
162
163 if ((*I)->getSelector() == S) {
164 MD = *I;
165 break;
166 }
167 }
168
169 if (!MD) { // No dealloc found.
170
171 const char* name = LOpts.getGCMode() == LangOptions::NonGC
172 ? "missing -dealloc"
173 : "missing -dealloc (Hybrid MM, non-GC)";
174
175 std::string buf;
176 llvm::raw_string_ostream os(buf);
177 os << "Objective-C class '" << D << "' lacks a 'dealloc' instance method";
178
179 BR.EmitBasicReport(name, os.str(), D->getLocStart());
180 return;
181 }
182
183 // dealloc found. Scan for missing [super dealloc].
184 if (MD->getBody() && !scan_dealloc(MD->getBody(), S)) {
185
186 const char* name = LOpts.getGCMode() == LangOptions::NonGC
187 ? "missing [super dealloc]"
188 : "missing [super dealloc] (Hybrid MM, non-GC)";
189
190 std::string buf;
191 llvm::raw_string_ostream os(buf);
192 os << "The 'dealloc' instance method in Objective-C class '" << D
193 << "' does not send a 'dealloc' message to its super class"
194 " (missing [super dealloc])";
195
196 BR.EmitBasicReport(name, os.str(), D->getLocStart());
197 return;
198 }
199
200 // Get the "release" selector.
201 IdentifierInfo* RII = &Ctx.Idents.get("release");
202 Selector RS = Ctx.Selectors.getSelector(0, &RII);
203
204 // Get the "self" identifier
205 IdentifierInfo* SelfII = &Ctx.Idents.get("self");
206
207 // Scan for missing and extra releases of ivars used by implementations
208 // of synthesized properties
209 for (ObjCImplementationDecl::propimpl_iterator I = D->propimpl_begin(),
210 E = D->propimpl_end(); I!=E; ++I) {
211
212 // We can only check the synthesized properties
213 if ((*I)->getPropertyImplementation() != ObjCPropertyImplDecl::Synthesize)
214 continue;
215
216 ObjCIvarDecl* ID = (*I)->getPropertyIvarDecl();
217 if (!ID)
218 continue;
219
220 QualType T = ID->getType();
221 if (!T->isObjCObjectPointerType()) // Skip non-pointer ivars
222 continue;
223
224 const ObjCPropertyDecl* PD = (*I)->getPropertyDecl();
225 if (!PD)
226 continue;
227
228 // ivars cannot be set via read-only properties, so we'll skip them
229 if (PD->isReadOnly())
230 continue;
231
232 // ivar must be released if and only if the kind of setter was not 'assign'
233 bool requiresRelease = PD->getSetterKind() != ObjCPropertyDecl::Assign;
234 if (scan_ivar_release(MD->getBody(), ID, PD, RS, SelfII, Ctx)
235 != requiresRelease) {
236 const char *name;
237 const char* category = "Memory (Core Foundation/Objective-C)";
238
239 std::string buf;
240 llvm::raw_string_ostream os(buf);
241
242 if (requiresRelease) {
243 name = LOpts.getGCMode() == LangOptions::NonGC
244 ? "missing ivar release (leak)"
245 : "missing ivar release (Hybrid MM, non-GC)";
246
247 os << "The '" << ID
248 << "' instance variable was retained by a synthesized property but "
249 "wasn't released in 'dealloc'";
250 } else {
251 name = LOpts.getGCMode() == LangOptions::NonGC
252 ? "extra ivar release (use-after-release)"
253 : "extra ivar release (Hybrid MM, non-GC)";
254
255 os << "The '" << ID
256 << "' instance variable was not retained by a synthesized property "
257 "but was released in 'dealloc'";
258 }
259
260 BR.EmitBasicReport(name, category, os.str(), (*I)->getLocation());
261 }
262 }
263 }
264
265 //===----------------------------------------------------------------------===//
266 // ObjCDeallocChecker
267 //===----------------------------------------------------------------------===//
268
269 namespace {
270 class ObjCDeallocChecker : public Checker<
271 check::ASTDecl<ObjCImplementationDecl> > {
272 public:
checkASTDecl(const ObjCImplementationDecl * D,AnalysisManager & mgr,BugReporter & BR) const273 void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
274 BugReporter &BR) const {
275 if (mgr.getLangOptions().getGCMode() == LangOptions::GCOnly)
276 return;
277 checkObjCDealloc(cast<ObjCImplementationDecl>(D), mgr.getLangOptions(), BR);
278 }
279 };
280 }
281
registerObjCDeallocChecker(CheckerManager & mgr)282 void ento::registerObjCDeallocChecker(CheckerManager &mgr) {
283 mgr.registerChecker<ObjCDeallocChecker>();
284 }
285