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/AST/Attr.h"
18 #include "clang/AST/DeclObjC.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/AST/ExprObjC.h"
21 #include "clang/Basic/LangOptions.h"
22 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
23 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
24 #include "clang/StaticAnalyzer/Core/Checker.h"
25 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
26 #include "llvm/Support/raw_ostream.h"
27
28 using namespace clang;
29 using namespace ento;
30
scan_dealloc(Stmt * S,Selector Dealloc)31 static bool scan_dealloc(Stmt *S, Selector Dealloc) {
32
33 if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S))
34 if (ME->getSelector() == Dealloc) {
35 switch (ME->getReceiverKind()) {
36 case ObjCMessageExpr::Instance: return false;
37 case ObjCMessageExpr::SuperInstance: return true;
38 case ObjCMessageExpr::Class: break;
39 case ObjCMessageExpr::SuperClass: break;
40 }
41 }
42
43 // Recurse to children.
44
45 for (Stmt::child_iterator I = S->child_begin(), E= S->child_end(); I!=E; ++I)
46 if (*I && scan_dealloc(*I, Dealloc))
47 return true;
48
49 return false;
50 }
51
scan_ivar_release(Stmt * S,ObjCIvarDecl * ID,const ObjCPropertyDecl * PD,Selector Release,IdentifierInfo * SelfII,ASTContext & Ctx)52 static bool scan_ivar_release(Stmt *S, ObjCIvarDecl *ID,
53 const ObjCPropertyDecl *PD,
54 Selector Release,
55 IdentifierInfo* SelfII,
56 ASTContext &Ctx) {
57
58 // [mMyIvar release]
59 if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S))
60 if (ME->getSelector() == Release)
61 if (ME->getInstanceReceiver())
62 if (Expr *Receiver = ME->getInstanceReceiver()->IgnoreParenCasts())
63 if (ObjCIvarRefExpr *E = dyn_cast<ObjCIvarRefExpr>(Receiver))
64 if (E->getDecl() == ID)
65 return true;
66
67 // [self setMyIvar:nil];
68 if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S))
69 if (ME->getInstanceReceiver())
70 if (Expr *Receiver = ME->getInstanceReceiver()->IgnoreParenCasts())
71 if (DeclRefExpr *E = dyn_cast<DeclRefExpr>(Receiver))
72 if (E->getDecl()->getIdentifier() == SelfII)
73 if (ME->getMethodDecl() == PD->getSetterMethodDecl() &&
74 ME->getNumArgs() == 1 &&
75 ME->getArg(0)->isNullPointerConstant(Ctx,
76 Expr::NPC_ValueDependentIsNull))
77 return true;
78
79 // self.myIvar = nil;
80 if (BinaryOperator* BO = dyn_cast<BinaryOperator>(S))
81 if (BO->isAssignmentOp())
82 if (ObjCPropertyRefExpr *PRE =
83 dyn_cast<ObjCPropertyRefExpr>(BO->getLHS()->IgnoreParenCasts()))
84 if (PRE->isExplicitProperty() && PRE->getExplicitProperty() == PD)
85 if (BO->getRHS()->isNullPointerConstant(Ctx,
86 Expr::NPC_ValueDependentIsNull)) {
87 // This is only a 'release' if the property kind is not
88 // 'assign'.
89 return PD->getSetterKind() != ObjCPropertyDecl::Assign;
90 }
91
92 // Recurse to children.
93 for (Stmt::child_iterator I = S->child_begin(), E= S->child_end(); I!=E; ++I)
94 if (*I && scan_ivar_release(*I, ID, PD, Release, SelfII, Ctx))
95 return true;
96
97 return false;
98 }
99
checkObjCDealloc(const CheckerBase * Checker,const ObjCImplementationDecl * D,const LangOptions & LOpts,BugReporter & BR)100 static void checkObjCDealloc(const CheckerBase *Checker,
101 const ObjCImplementationDecl *D,
102 const LangOptions &LOpts, BugReporter &BR) {
103
104 assert (LOpts.getGC() != LangOptions::GCOnly);
105
106 ASTContext &Ctx = BR.getContext();
107 const ObjCInterfaceDecl *ID = D->getClassInterface();
108
109 // Does the class contain any ivars that are pointers (or id<...>)?
110 // If not, skip the check entirely.
111 // NOTE: This is motivated by PR 2517:
112 // http://llvm.org/bugs/show_bug.cgi?id=2517
113
114 bool containsPointerIvar = false;
115
116 for (const auto *Ivar : ID->ivars()) {
117 QualType T = Ivar->getType();
118
119 if (!T->isObjCObjectPointerType() ||
120 Ivar->hasAttr<IBOutletAttr>() || // Skip IBOutlets.
121 Ivar->hasAttr<IBOutletCollectionAttr>()) // Skip IBOutletCollections.
122 continue;
123
124 containsPointerIvar = true;
125 break;
126 }
127
128 if (!containsPointerIvar)
129 return;
130
131 // Determine if the class subclasses NSObject.
132 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
133 IdentifierInfo* SenTestCaseII = &Ctx.Idents.get("SenTestCase");
134
135
136 for ( ; ID ; ID = ID->getSuperClass()) {
137 IdentifierInfo *II = ID->getIdentifier();
138
139 if (II == NSObjectII)
140 break;
141
142 // FIXME: For now, ignore classes that subclass SenTestCase, as these don't
143 // need to implement -dealloc. They implement tear down in another way,
144 // which we should try and catch later.
145 // http://llvm.org/bugs/show_bug.cgi?id=3187
146 if (II == SenTestCaseII)
147 return;
148 }
149
150 if (!ID)
151 return;
152
153 // Get the "dealloc" selector.
154 IdentifierInfo* II = &Ctx.Idents.get("dealloc");
155 Selector S = Ctx.Selectors.getSelector(0, &II);
156 const ObjCMethodDecl *MD = nullptr;
157
158 // Scan the instance methods for "dealloc".
159 for (const auto *I : D->instance_methods()) {
160 if (I->getSelector() == S) {
161 MD = I;
162 break;
163 }
164 }
165
166 PathDiagnosticLocation DLoc =
167 PathDiagnosticLocation::createBegin(D, BR.getSourceManager());
168
169 if (!MD) { // No dealloc found.
170
171 const char* name = LOpts.getGC() == 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(D, Checker, name, categories::CoreFoundationObjectiveC,
180 os.str(), DLoc);
181 return;
182 }
183
184 // dealloc found. Scan for missing [super dealloc].
185 if (MD->getBody() && !scan_dealloc(MD->getBody(), S)) {
186
187 const char* name = LOpts.getGC() == LangOptions::NonGC
188 ? "missing [super dealloc]"
189 : "missing [super dealloc] (Hybrid MM, non-GC)";
190
191 std::string buf;
192 llvm::raw_string_ostream os(buf);
193 os << "The 'dealloc' instance method in Objective-C class '" << *D
194 << "' does not send a 'dealloc' message to its super class"
195 " (missing [super dealloc])";
196
197 BR.EmitBasicReport(MD, Checker, name, categories::CoreFoundationObjectiveC,
198 os.str(), DLoc);
199 return;
200 }
201
202 // Get the "release" selector.
203 IdentifierInfo* RII = &Ctx.Idents.get("release");
204 Selector RS = Ctx.Selectors.getSelector(0, &RII);
205
206 // Get the "self" identifier
207 IdentifierInfo* SelfII = &Ctx.Idents.get("self");
208
209 // Scan for missing and extra releases of ivars used by implementations
210 // of synthesized properties
211 for (const auto *I : D->property_impls()) {
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 = nullptr;
237 std::string buf;
238 llvm::raw_string_ostream os(buf);
239
240 if (requiresRelease) {
241 name = LOpts.getGC() == LangOptions::NonGC
242 ? "missing ivar release (leak)"
243 : "missing ivar release (Hybrid MM, non-GC)";
244
245 os << "The '" << *ID
246 << "' instance variable was retained by a synthesized property but "
247 "wasn't released in 'dealloc'";
248 } else {
249 name = LOpts.getGC() == LangOptions::NonGC
250 ? "extra ivar release (use-after-release)"
251 : "extra ivar release (Hybrid MM, non-GC)";
252
253 os << "The '" << *ID
254 << "' instance variable was not retained by a synthesized property "
255 "but was released in 'dealloc'";
256 }
257
258 PathDiagnosticLocation SDLoc =
259 PathDiagnosticLocation::createBegin(I, BR.getSourceManager());
260
261 BR.EmitBasicReport(MD, Checker, name,
262 categories::CoreFoundationObjectiveC, os.str(), SDLoc);
263 }
264 }
265 }
266
267 //===----------------------------------------------------------------------===//
268 // ObjCDeallocChecker
269 //===----------------------------------------------------------------------===//
270
271 namespace {
272 class ObjCDeallocChecker : public Checker<
273 check::ASTDecl<ObjCImplementationDecl> > {
274 public:
checkASTDecl(const ObjCImplementationDecl * D,AnalysisManager & mgr,BugReporter & BR) const275 void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
276 BugReporter &BR) const {
277 if (mgr.getLangOpts().getGC() == LangOptions::GCOnly)
278 return;
279 checkObjCDealloc(this, cast<ObjCImplementationDecl>(D), mgr.getLangOpts(),
280 BR);
281 }
282 };
283 }
284
registerObjCDeallocChecker(CheckerManager & mgr)285 void ento::registerObjCDeallocChecker(CheckerManager &mgr) {
286 mgr.registerChecker<ObjCDeallocChecker>();
287 }
288