ObjCAtSyncChecker.cpp revision 9b663716449b618ba0390b1dbebc54fa8e971124 
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 "InternalChecks.h"
16#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17#include "clang/StaticAnalyzer/Checkers/DereferenceChecker.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerVisitor.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class ObjCAtSyncChecker : public CheckerVisitor<ObjCAtSyncChecker> {
26  BuiltinBug *BT_null;
27  BuiltinBug *BT_undef;
28public:
29  ObjCAtSyncChecker() : BT_null(0), BT_undef(0) {}
30  static void *getTag() { static int tag = 0; return &tag; }
31  void PreVisitObjCAtSynchronizedStmt(CheckerContext &C,
32                                      const ObjCAtSynchronizedStmt *S);
33};
34} // end anonymous namespace
35
36void ento::RegisterObjCAtSyncChecker(ExprEngine &Eng) {
37  // @synchronized is an Objective-C 2 feature.
38  if (Eng.getContext().getLangOptions().ObjC2)
39    Eng.registerCheck(new ObjCAtSyncChecker());
40}
41
42void ObjCAtSyncChecker::PreVisitObjCAtSynchronizedStmt(CheckerContext &C,
43                                         const ObjCAtSynchronizedStmt *S) {
44
45  const Expr *Ex = S->getSynchExpr();
46  const GRState *state = C.getState();
47  SVal V = state->getSVal(Ex);
48
49  // Uninitialized value used for the mutex?
50  if (isa<UndefinedVal>(V)) {
51    if (ExplodedNode *N = C.generateSink()) {
52      if (!BT_undef)
53        BT_undef = new BuiltinBug("Uninitialized value used as mutex "
54                                  "for @synchronized");
55      EnhancedBugReport *report =
56        new EnhancedBugReport(*BT_undef, BT_undef->getDescription(), N);
57      report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, Ex);
58      C.EmitReport(report);
59    }
60    return;
61  }
62
63  if (V.isUnknown())
64    return;
65
66  // Check for null mutexes.
67  const GRState *notNullState, *nullState;
68  llvm::tie(notNullState, nullState) = state->assume(cast<DefinedSVal>(V));
69
70  if (nullState) {
71    if (!notNullState) {
72      // Generate an error node.  This isn't a sink since
73      // a null mutex just means no synchronization occurs.
74      if (ExplodedNode *N = C.generateNode(nullState)) {
75        if (!BT_null)
76          BT_null = new BuiltinBug("Nil value used as mutex for @synchronized() "
77                                   "(no synchronization will occur)");
78        EnhancedBugReport *report =
79          new EnhancedBugReport(*BT_null, BT_null->getDescription(), N);
80        report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
81                                  Ex);
82
83        C.EmitReport(report);
84        return;
85      }
86    }
87    // Don't add a transition for 'nullState'.  If the value is
88    // under-constrained to be null or non-null, assume it is non-null
89    // afterwards.
90  }
91
92  if (notNullState)
93    C.addTransition(notNullState);
94}
95
96