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