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
28using namespace clang;
29using namespace ento;
30
31static 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
52static 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
100static 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
271namespace {
272class ObjCDeallocChecker : public Checker<
273                                      check::ASTDecl<ObjCImplementationDecl> > {
274public:
275  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
285void ento::registerObjCDeallocChecker(CheckerManager &mgr) {
286  mgr.registerChecker<ObjCDeallocChecker>();
287}
288