1//=- DirectIvarAssignment.cpp - Check rules on ObjC properties -*- 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//  Check that Objective C properties are set with the setter, not though a
11//      direct assignment.
12//
13//  Two versions of a checker exist: one that checks all methods and the other
14//      that only checks the methods annotated with
15//      __attribute__((annotate("objc_no_direct_instance_variable_assignment")))
16//
17//  The checker does not warn about assignments to Ivars, annotated with
18//       __attribute__((objc_allow_direct_instance_variable_assignment"))). This
19//      annotation serves as a false positive suppression mechanism for the
20//      checker. The annotation is allowed on properties and Ivars.
21//
22//===----------------------------------------------------------------------===//
23
24#include "ClangSACheckers.h"
25#include "clang/AST/Attr.h"
26#include "clang/AST/DeclObjC.h"
27#include "clang/AST/StmtVisitor.h"
28#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
29#include "clang/StaticAnalyzer/Core/Checker.h"
30#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
31#include "llvm/ADT/DenseMap.h"
32
33using namespace clang;
34using namespace ento;
35
36namespace {
37
38/// The default method filter, which is used to filter out the methods on which
39/// the check should not be performed.
40///
41/// Checks for the init, dealloc, and any other functions that might be allowed
42/// to perform direct instance variable assignment based on their name.
43static bool DefaultMethodFilter(const ObjCMethodDecl *M) {
44  if (M->getMethodFamily() == OMF_init || M->getMethodFamily() == OMF_dealloc ||
45      M->getMethodFamily() == OMF_copy ||
46      M->getMethodFamily() == OMF_mutableCopy ||
47      M->getSelector().getNameForSlot(0).find("init") != StringRef::npos ||
48      M->getSelector().getNameForSlot(0).find("Init") != StringRef::npos)
49    return true;
50  return false;
51}
52
53class DirectIvarAssignment :
54  public Checker<check::ASTDecl<ObjCImplementationDecl> > {
55
56  typedef llvm::DenseMap<const ObjCIvarDecl*,
57                         const ObjCPropertyDecl*> IvarToPropertyMapTy;
58
59  /// A helper class, which walks the AST and locates all assignments to ivars
60  /// in the given function.
61  class MethodCrawler : public ConstStmtVisitor<MethodCrawler> {
62    const IvarToPropertyMapTy &IvarToPropMap;
63    const ObjCMethodDecl *MD;
64    const ObjCInterfaceDecl *InterfD;
65    BugReporter &BR;
66    const CheckerBase *Checker;
67    LocationOrAnalysisDeclContext DCtx;
68
69  public:
70    MethodCrawler(const IvarToPropertyMapTy &InMap, const ObjCMethodDecl *InMD,
71                  const ObjCInterfaceDecl *InID, BugReporter &InBR,
72                  const CheckerBase *Checker, AnalysisDeclContext *InDCtx)
73        : IvarToPropMap(InMap), MD(InMD), InterfD(InID), BR(InBR),
74          Checker(Checker), DCtx(InDCtx) {}
75
76    void VisitStmt(const Stmt *S) { VisitChildren(S); }
77
78    void VisitBinaryOperator(const BinaryOperator *BO);
79
80    void VisitChildren(const Stmt *S) {
81      for (Stmt::const_child_range I = S->children(); I; ++I)
82        if (*I)
83         this->Visit(*I);
84    }
85  };
86
87public:
88  bool (*ShouldSkipMethod)(const ObjCMethodDecl *);
89
90  DirectIvarAssignment() : ShouldSkipMethod(&DefaultMethodFilter) {}
91
92  void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& Mgr,
93                    BugReporter &BR) const;
94};
95
96static const ObjCIvarDecl *findPropertyBackingIvar(const ObjCPropertyDecl *PD,
97                                               const ObjCInterfaceDecl *InterD,
98                                               ASTContext &Ctx) {
99  // Check for synthesized ivars.
100  ObjCIvarDecl *ID = PD->getPropertyIvarDecl();
101  if (ID)
102    return ID;
103
104  ObjCInterfaceDecl *NonConstInterD = const_cast<ObjCInterfaceDecl*>(InterD);
105
106  // Check for existing "_PropName".
107  ID = NonConstInterD->lookupInstanceVariable(PD->getDefaultSynthIvarName(Ctx));
108  if (ID)
109    return ID;
110
111  // Check for existing "PropName".
112  IdentifierInfo *PropIdent = PD->getIdentifier();
113  ID = NonConstInterD->lookupInstanceVariable(PropIdent);
114
115  return ID;
116}
117
118void DirectIvarAssignment::checkASTDecl(const ObjCImplementationDecl *D,
119                                       AnalysisManager& Mgr,
120                                       BugReporter &BR) const {
121  const ObjCInterfaceDecl *InterD = D->getClassInterface();
122
123
124  IvarToPropertyMapTy IvarToPropMap;
125
126  // Find all properties for this class.
127  for (const auto *PD : InterD->properties()) {
128    // Find the corresponding IVar.
129    const ObjCIvarDecl *ID = findPropertyBackingIvar(PD, InterD,
130                                                     Mgr.getASTContext());
131
132    if (!ID)
133      continue;
134
135    // Store the IVar to property mapping.
136    IvarToPropMap[ID] = PD;
137  }
138
139  if (IvarToPropMap.empty())
140    return;
141
142  for (const auto *M : D->instance_methods()) {
143    AnalysisDeclContext *DCtx = Mgr.getAnalysisDeclContext(M);
144
145    if ((*ShouldSkipMethod)(M))
146      continue;
147
148    const Stmt *Body = M->getBody();
149    assert(Body);
150
151    MethodCrawler MC(IvarToPropMap, M->getCanonicalDecl(), InterD, BR, this,
152                     DCtx);
153    MC.VisitStmt(Body);
154  }
155}
156
157static bool isAnnotatedToAllowDirectAssignment(const Decl *D) {
158  for (const auto *Ann : D->specific_attrs<AnnotateAttr>())
159    if (Ann->getAnnotation() ==
160        "objc_allow_direct_instance_variable_assignment")
161      return true;
162  return false;
163}
164
165void DirectIvarAssignment::MethodCrawler::VisitBinaryOperator(
166                                                    const BinaryOperator *BO) {
167  if (!BO->isAssignmentOp())
168    return;
169
170  const ObjCIvarRefExpr *IvarRef =
171          dyn_cast<ObjCIvarRefExpr>(BO->getLHS()->IgnoreParenCasts());
172
173  if (!IvarRef)
174    return;
175
176  if (const ObjCIvarDecl *D = IvarRef->getDecl()) {
177    IvarToPropertyMapTy::const_iterator I = IvarToPropMap.find(D);
178
179    if (I != IvarToPropMap.end()) {
180      const ObjCPropertyDecl *PD = I->second;
181      // Skip warnings on Ivars, annotated with
182      // objc_allow_direct_instance_variable_assignment. This annotation serves
183      // as a false positive suppression mechanism for the checker. The
184      // annotation is allowed on properties and ivars.
185      if (isAnnotatedToAllowDirectAssignment(PD) ||
186          isAnnotatedToAllowDirectAssignment(D))
187        return;
188
189      ObjCMethodDecl *GetterMethod =
190          InterfD->getInstanceMethod(PD->getGetterName());
191      ObjCMethodDecl *SetterMethod =
192          InterfD->getInstanceMethod(PD->getSetterName());
193
194      if (SetterMethod && SetterMethod->getCanonicalDecl() == MD)
195        return;
196
197      if (GetterMethod && GetterMethod->getCanonicalDecl() == MD)
198        return;
199
200      BR.EmitBasicReport(
201          MD, Checker, "Property access", categories::CoreFoundationObjectiveC,
202          "Direct assignment to an instance variable backing a property; "
203          "use the setter instead",
204          PathDiagnosticLocation(IvarRef, BR.getSourceManager(), DCtx));
205    }
206  }
207}
208}
209
210// Register the checker that checks for direct accesses in all functions,
211// except for the initialization and copy routines.
212void ento::registerDirectIvarAssignment(CheckerManager &mgr) {
213  mgr.registerChecker<DirectIvarAssignment>();
214}
215
216// Register the checker that checks for direct accesses in functions annotated
217// with __attribute__((annotate("objc_no_direct_instance_variable_assignment"))).
218static bool AttrFilter(const ObjCMethodDecl *M) {
219  for (const auto *Ann : M->specific_attrs<AnnotateAttr>())
220    if (Ann->getAnnotation() == "objc_no_direct_instance_variable_assignment")
221      return false;
222  return true;
223}
224
225void ento::registerDirectIvarAssignmentForAnnotatedFunctions(
226    CheckerManager &mgr) {
227  mgr.registerChecker<DirectIvarAssignment>()->ShouldSkipMethod = &AttrFilter;
228}
229