clang/lib/StaticAnalyzer/Checkers/DirectIvarAssignment.cpp

   1 //=- DirectIvarAssignment.cpp - Check rules on ObjC properties -*- C++ ----*-==//
   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 //  Check that Objective C properties are set with the setter, not though a
  10 //      direct assignment.
  11 //
  12 //  Two versions of a checker exist: one that checks all methods and the other
  13 //      that only checks the methods annotated with
  14 //      __attribute__((annotate("objc_no_direct_instance_variable_assignment")))
  15 //
  16 //  The checker does not warn about assignments to Ivars, annotated with
  17 //       __attribute__((objc_allow_direct_instance_variable_assignment"))). This
  18 //      annotation serves as a false positive suppression mechanism for the
  19 //      checker. The annotation is allowed on properties and Ivars.
  20 //
  21 //===----------------------------------------------------------------------===//
  22
  23 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  24 #include "clang/AST/Attr.h"
  25 #include "clang/AST/DeclObjC.h"
  26 #include "clang/AST/StmtVisitor.h"
  27 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
  28 #include "clang/StaticAnalyzer/Core/Checker.h"
  29 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
  30 #include "llvm/ADT/DenseMap.h"
  31
  32 using namespace clang;
  33 using namespace ento;
  34
  35 namespace {
  36
  37 /// The default method filter, which is used to filter out the methods on which
  38 /// the check should not be performed.
  39 ///
  40 /// Checks for the init, dealloc, and any other functions that might be allowed
  41 /// to perform direct instance variable assignment based on their name.
  42 static bool DefaultMethodFilter(const ObjCMethodDecl *M) {
  43   return M->getMethodFamily() == OMF_init ||
  44          M->getMethodFamily() == OMF_dealloc ||
  45          M->getMethodFamily() == OMF_copy ||
  46          M->getMethodFamily() == OMF_mutableCopy ||
  47          M->getSelector().getNameForSlot(0).contains("init") ||
  48          M->getSelector().getNameForSlot(0).contains("Init");
  49 }
  50
  51 class DirectIvarAssignment :
  52   public Checker<check::ASTDecl<ObjCImplementationDecl> > {
  53
  54   typedef llvm::DenseMap<const ObjCIvarDecl*,
  55                          const ObjCPropertyDecl*> IvarToPropertyMapTy;
  56
  57   /// A helper class, which walks the AST and locates all assignments to ivars
  58   /// in the given function.
  59   class MethodCrawler : public ConstStmtVisitor<MethodCrawler> {
  60     const IvarToPropertyMapTy &IvarToPropMap;
  61     const ObjCMethodDecl *MD;
  62     const ObjCInterfaceDecl *InterfD;
  63     BugReporter &BR;
  64     const CheckerBase *Checker;
  65     LocationOrAnalysisDeclContext DCtx;
  66
  67   public:
  68     MethodCrawler(const IvarToPropertyMapTy &InMap, const ObjCMethodDecl *InMD,
  69                   const ObjCInterfaceDecl *InID, BugReporter &InBR,
  70                   const CheckerBase *Checker, AnalysisDeclContext *InDCtx)
  71         : IvarToPropMap(InMap), MD(InMD), InterfD(InID), BR(InBR),
  72           Checker(Checker), DCtx(InDCtx) {}
  73
  74     void VisitStmt(const Stmt *S) { VisitChildren(S); }
  75
  76     void VisitBinaryOperator(const BinaryOperator *BO);
  77
  78     void VisitChildren(const Stmt *S) {
  79       for (const Stmt *Child : S->children())
  80         if (Child)
  81           this->Visit(Child);
  82     }
  83   };
  84
  85 public:
  86   bool (*ShouldSkipMethod)(const ObjCMethodDecl *);
  87
  88   DirectIvarAssignment() : ShouldSkipMethod(&DefaultMethodFilter) {}
  89
  90   void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& Mgr,
  91                     BugReporter &BR) const;
  92 };
  93
  94 static const ObjCIvarDecl *findPropertyBackingIvar(const ObjCPropertyDecl *PD,
  95                                                const ObjCInterfaceDecl *InterD,
  96                                                ASTContext &Ctx) {
  97   // Check for synthesized ivars.
  98   ObjCIvarDecl *ID = PD->getPropertyIvarDecl();
  99   if (ID)
 100     return ID;
 101
 102   ObjCInterfaceDecl *NonConstInterD = const_cast<ObjCInterfaceDecl*>(InterD);
 103
 104   // Check for existing "_PropName".
 105   ID = NonConstInterD->lookupInstanceVariable(PD->getDefaultSynthIvarName(Ctx));
 106   if (ID)
 107     return ID;
 108
 109   // Check for existing "PropName".
 110   IdentifierInfo *PropIdent = PD->getIdentifier();
 111   ID = NonConstInterD->lookupInstanceVariable(PropIdent);
 112
 113   return ID;
 114 }
 115
 116 void DirectIvarAssignment::checkASTDecl(const ObjCImplementationDecl *D,
 117                                        AnalysisManager& Mgr,
 118                                        BugReporter &BR) const {
 119   const ObjCInterfaceDecl *InterD = D->getClassInterface();
 120
 121
 122   IvarToPropertyMapTy IvarToPropMap;
 123
 124   // Find all properties for this class.
 125   for (const auto *PD : InterD->instance_properties()) {
 126     // Find the corresponding IVar.
 127     const ObjCIvarDecl *ID = findPropertyBackingIvar(PD, InterD,
 128                                                      Mgr.getASTContext());
 129
 130     if (!ID)
 131       continue;
 132
 133     // Store the IVar to property mapping.
 134     IvarToPropMap[ID] = PD;
 135   }
 136
 137   if (IvarToPropMap.empty())
 138     return;
 139
 140   for (const auto *M : D->instance_methods()) {
 141     AnalysisDeclContext *DCtx = Mgr.getAnalysisDeclContext(M);
 142
 143     if ((*ShouldSkipMethod)(M))
 144       continue;
 145
 146     const Stmt *Body = M->getBody();
 147     if (M->isSynthesizedAccessorStub())
 148       continue;
 149     assert(Body);
 150
 151     MethodCrawler MC(IvarToPropMap, M->getCanonicalDecl(), InterD, BR, this,
 152                      DCtx);
 153     MC.VisitStmt(Body);
 154   }
 155 }
 156
 157 static 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
 165 void 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 functions annotated
 211 // with __attribute__((annotate("objc_no_direct_instance_variable_assignment"))).
 212 static bool AttrFilter(const ObjCMethodDecl *M) {
 213   for (const auto *Ann : M->specific_attrs<AnnotateAttr>())
 214     if (Ann->getAnnotation() == "objc_no_direct_instance_variable_assignment")
 215       return false;
 216   return true;
 217 }
 218
 219 // Register the checker that checks for direct accesses in all functions,
 220 // except for the initialization and copy routines.
 221 void ento::registerDirectIvarAssignment(CheckerManager &mgr) {
 222   auto Chk = mgr.registerChecker<DirectIvarAssignment>();
 223   if (mgr.getAnalyzerOptions().getCheckerBooleanOption(Chk,
 224                                                        "AnnotatedFunctions"))
 225     Chk->ShouldSkipMethod = &AttrFilter;
 226 }
 227
 228 bool ento::shouldRegisterDirectIvarAssignment(const CheckerManager &mgr) {
 229   return true;
 230 }