1 //== ObjCAtSyncChecker.cpp - nil mutex checker for @synchronized -*- 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 defines ObjCAtSyncChecker, a builtin check that checks for null pointers 11 // used as mutexes for @synchronized. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/AST/StmtObjC.h" 17 #include "clang/StaticAnalyzer/Core/Checker.h" 18 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 20 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 21 #include "clang/StaticAnalyzer/Checkers/DereferenceChecker.h" 22 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 23 #include "llvm/ADT/STLExtras.h" 24 25 using namespace clang; 26 using namespace ento; 27 28 namespace { 29 class ObjCAtSyncChecker 30 : public Checker< check::PreStmt<ObjCAtSynchronizedStmt> > { 31 mutable llvm::OwningPtr<BuiltinBug> BT_null; 32 mutable llvm::OwningPtr<BuiltinBug> BT_undef; 33 34 public: 35 void checkPreStmt(const ObjCAtSynchronizedStmt *S, CheckerContext &C) const; 36 }; 37 } // end anonymous namespace 38 39 void ObjCAtSyncChecker::checkPreStmt(const ObjCAtSynchronizedStmt *S, 40 CheckerContext &C) const { 41 42 const Expr *Ex = S->getSynchExpr(); 43 ProgramStateRef state = C.getState(); 44 SVal V = state->getSVal(Ex, C.getLocationContext()); 45 46 // Uninitialized value used for the mutex? 47 if (isa<UndefinedVal>(V)) { 48 if (ExplodedNode *N = C.generateSink()) { 49 if (!BT_undef) 50 BT_undef.reset(new BuiltinBug("Uninitialized value used as mutex " 51 "for @synchronized")); 52 BugReport *report = 53 new BugReport(*BT_undef, BT_undef->getDescription(), N); 54 report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, Ex)); 55 C.EmitReport(report); 56 } 57 return; 58 } 59 60 if (V.isUnknown()) 61 return; 62 63 // Check for null mutexes. 64 ProgramStateRef notNullState, nullState; 65 llvm::tie(notNullState, nullState) = state->assume(cast<DefinedSVal>(V)); 66 67 if (nullState) { 68 if (!notNullState) { 69 // Generate an error node. This isn't a sink since 70 // a null mutex just means no synchronization occurs. 71 if (ExplodedNode *N = C.addTransition(nullState)) { 72 if (!BT_null) 73 BT_null.reset(new BuiltinBug("Nil value used as mutex for @synchronized() " 74 "(no synchronization will occur)")); 75 BugReport *report = 76 new BugReport(*BT_null, BT_null->getDescription(), N); 77 report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, Ex)); 78 79 C.EmitReport(report); 80 return; 81 } 82 } 83 // Don't add a transition for 'nullState'. If the value is 84 // under-constrained to be null or non-null, assume it is non-null 85 // afterwards. 86 } 87 88 if (notNullState) 89 C.addTransition(notNullState); 90 } 91 92 void ento::registerObjCAtSyncChecker(CheckerManager &mgr) { 93 if (mgr.getLangOptions().ObjC2) 94 mgr.registerChecker<ObjCAtSyncChecker>(); 95 } 96