clang  10.0.0svn
NonNullParamChecker.cpp
Go to the documentation of this file.
1 //===--- NonNullParamChecker.cpp - Undefined arguments checker -*- 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 // This defines NonNullParamChecker, which checks for arguments expected not to
10 // be null due to:
11 // - the corresponding parameters being declared to have nonnull attribute
12 // - the corresponding parameters being references; since the call would form
13 // a reference to a null pointer
14 //
15 //===----------------------------------------------------------------------===//
16 
18 #include "clang/AST/Attr.h"
24 
25 using namespace clang;
26 using namespace ento;
27 
28 namespace {
29 class NonNullParamChecker
30  : public Checker< check::PreCall, EventDispatcher<ImplicitNullDerefEvent> > {
31  mutable std::unique_ptr<BugType> BTAttrNonNull;
32  mutable std::unique_ptr<BugType> BTNullRefArg;
33 
34 public:
35 
36  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
37 
38  std::unique_ptr<PathSensitiveBugReport>
39  genReportNullAttrNonNull(const ExplodedNode *ErrorN,
40  const Expr *ArgE,
41  unsigned IdxOfArg) const;
42  std::unique_ptr<PathSensitiveBugReport>
43  genReportReferenceToNullPointer(const ExplodedNode *ErrorN,
44  const Expr *ArgE) const;
45 };
46 } // end anonymous namespace
47 
48 /// \return Bitvector marking non-null attributes.
49 static llvm::SmallBitVector getNonNullAttrs(const CallEvent &Call) {
50  const Decl *FD = Call.getDecl();
51  unsigned NumArgs = Call.getNumArgs();
52  llvm::SmallBitVector AttrNonNull(NumArgs);
53  for (const auto *NonNull : FD->specific_attrs<NonNullAttr>()) {
54  if (!NonNull->args_size()) {
55  AttrNonNull.set(0, NumArgs);
56  break;
57  }
58  for (const ParamIdx &Idx : NonNull->args()) {
59  unsigned IdxAST = Idx.getASTIndex();
60  if (IdxAST >= NumArgs)
61  continue;
62  AttrNonNull.set(IdxAST);
63  }
64  }
65  return AttrNonNull;
66 }
67 
68 void NonNullParamChecker::checkPreCall(const CallEvent &Call,
69  CheckerContext &C) const {
70  if (!Call.getDecl())
71  return;
72 
73  llvm::SmallBitVector AttrNonNull = getNonNullAttrs(Call);
74  unsigned NumArgs = Call.getNumArgs();
75 
76  ProgramStateRef state = C.getState();
77  ArrayRef<ParmVarDecl*> parms = Call.parameters();
78 
79  for (unsigned idx = 0; idx < NumArgs; ++idx) {
80  // For vararg functions, a corresponding parameter decl may not exist.
81  bool HasParam = idx < parms.size();
82 
83  // Check if the parameter is a reference. We want to report when reference
84  // to a null pointer is passed as a parameter.
85  bool haveRefTypeParam =
86  HasParam ? parms[idx]->getType()->isReferenceType() : false;
87  bool haveAttrNonNull = AttrNonNull[idx];
88 
89  // Check if the parameter is also marked 'nonnull'.
90  if (!haveAttrNonNull && HasParam)
91  haveAttrNonNull = parms[idx]->hasAttr<NonNullAttr>();
92 
93  if (!haveAttrNonNull && !haveRefTypeParam)
94  continue;
95 
96  // If the value is unknown or undefined, we can't perform this check.
97  const Expr *ArgE = Call.getArgExpr(idx);
98  SVal V = Call.getArgSVal(idx);
99  auto DV = V.getAs<DefinedSVal>();
100  if (!DV)
101  continue;
102 
103  assert(!haveRefTypeParam || DV->getAs<Loc>());
104 
105  // Process the case when the argument is not a location.
106  if (haveAttrNonNull && !DV->getAs<Loc>()) {
107  // If the argument is a union type, we want to handle a potential
108  // transparent_union GCC extension.
109  if (!ArgE)
110  continue;
111 
112  QualType T = ArgE->getType();
113  const RecordType *UT = T->getAsUnionType();
114  if (!UT || !UT->getDecl()->hasAttr<TransparentUnionAttr>())
115  continue;
116 
117  auto CSV = DV->getAs<nonloc::CompoundVal>();
118 
119  // FIXME: Handle LazyCompoundVals?
120  if (!CSV)
121  continue;
122 
123  V = *(CSV->begin());
124  DV = V.getAs<DefinedSVal>();
125  assert(++CSV->begin() == CSV->end());
126  // FIXME: Handle (some_union){ some_other_union_val }, which turns into
127  // a LazyCompoundVal inside a CompoundVal.
128  if (!V.getAs<Loc>())
129  continue;
130 
131  // Retrieve the corresponding expression.
132  if (const auto *CE = dyn_cast<CompoundLiteralExpr>(ArgE))
133  if (const auto *IE = dyn_cast<InitListExpr>(CE->getInitializer()))
134  ArgE = dyn_cast<Expr>(*(IE->begin()));
135  }
136 
137  ConstraintManager &CM = C.getConstraintManager();
138  ProgramStateRef stateNotNull, stateNull;
139  std::tie(stateNotNull, stateNull) = CM.assumeDual(state, *DV);
140 
141  // Generate an error node. Check for a null node in case
142  // we cache out.
143  if (stateNull && !stateNotNull) {
144  if (ExplodedNode *errorNode = C.generateErrorNode(stateNull)) {
145 
146  std::unique_ptr<BugReport> R;
147  if (haveAttrNonNull)
148  R = genReportNullAttrNonNull(errorNode, ArgE, idx + 1);
149  else if (haveRefTypeParam)
150  R = genReportReferenceToNullPointer(errorNode, ArgE);
151 
152  // Highlight the range of the argument that was null.
153  R->addRange(Call.getArgSourceRange(idx));
154 
155  // Emit the bug report.
156  C.emitReport(std::move(R));
157  }
158 
159  // Always return. Either we cached out or we just emitted an error.
160  return;
161  }
162 
163  if (stateNull) {
164  if (ExplodedNode *N = C.generateSink(stateNull, C.getPredecessor())) {
165  ImplicitNullDerefEvent event = {
166  V, false, N, &C.getBugReporter(),
167  /*IsDirectDereference=*/haveRefTypeParam};
168  dispatchEvent(event);
169  }
170  }
171 
172  // If a pointer value passed the check we should assume that it is
173  // indeed not null from this point forward.
174  state = stateNotNull;
175  }
176 
177  // If we reach here all of the arguments passed the nonnull check.
178  // If 'state' has been updated generated a new node.
179  C.addTransition(state);
180 }
181 
182 std::unique_ptr<PathSensitiveBugReport>
183 NonNullParamChecker::genReportNullAttrNonNull(const ExplodedNode *ErrorNode,
184  const Expr *ArgE,
185  unsigned IdxOfArg) const {
186  // Lazily allocate the BugType object if it hasn't already been
187  // created. Ownership is transferred to the BugReporter object once
188  // the BugReport is passed to 'EmitWarning'.
189  if (!BTAttrNonNull)
190  BTAttrNonNull.reset(new BugType(
191  this, "Argument with 'nonnull' attribute passed null", "API"));
192 
194  llvm::raw_svector_ostream OS(SBuf);
195  OS << "Null pointer passed to "
196  << IdxOfArg << llvm::getOrdinalSuffix(IdxOfArg)
197  << " parameter expecting 'nonnull'";
198 
199  auto R =
200  std::make_unique<PathSensitiveBugReport>(*BTAttrNonNull, SBuf, ErrorNode);
201  if (ArgE)
202  bugreporter::trackExpressionValue(ErrorNode, ArgE, *R);
203 
204  return R;
205 }
206 
207 std::unique_ptr<PathSensitiveBugReport>
208 NonNullParamChecker::genReportReferenceToNullPointer(
209  const ExplodedNode *ErrorNode, const Expr *ArgE) const {
210  if (!BTNullRefArg)
211  BTNullRefArg.reset(new BuiltinBug(this, "Dereference of null pointer"));
212 
213  auto R = std::make_unique<PathSensitiveBugReport>(
214  *BTNullRefArg, "Forming reference to null pointer", ErrorNode);
215  if (ArgE) {
216  const Expr *ArgEDeref = bugreporter::getDerefExpr(ArgE);
217  if (!ArgEDeref)
218  ArgEDeref = ArgE;
219  bugreporter::trackExpressionValue(ErrorNode, ArgEDeref, *R);
220  }
221  return R;
222 
223 }
224 
225 void ento::registerNonNullParamChecker(CheckerManager &mgr) {
226  mgr.registerChecker<NonNullParamChecker>();
227 }
228 
229 bool ento::shouldRegisterNonNullParamChecker(const LangOptions &LO) {
230  return true;
231 }
A (possibly-)qualified type.
Definition: Type.h:643
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:88
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
const RecordType * getAsUnionType() const
NOTE: getAs*ArrayType are methods on ASTContext.
Definition: Type.cpp:592
const T * getAs() const
Member-template getAs<specific type>&#39;.
Definition: Type.h:6858
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:49
i32 captured_struct **param SharedsTy A type which contains references the shared variables *param Shareds Context with the list of shared variables from the p *TaskFunction *param Data Additional data for task generation like final * state
Values of this type can never be null.
bool hasAttr() const
Definition: DeclBase.h:542
A single parameter index whose accessors require each use to make explicit the parameter index encodi...
Definition: Attr.h:212
This represents one expression.
Definition: Expr.h:108
#define V(N, I)
Definition: ASTContext.h:2921
QualType getType() const
Definition: Expr.h:137
static llvm::SmallBitVector getNonNullAttrs(const CallEvent &Call)
RecordDecl * getDecl() const
Definition: Type.h:4454
Dataflow Directional Tag Classes.
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:4444
Indicates that the tracking object is a descendant of a referenced-counted OSObject, used in the Darwin kernel.
llvm::iterator_range< specific_attr_iterator< T > > specific_attrs() const
Definition: DeclBase.h:524