clang  10.0.0svn
ExprEngineObjC.cpp
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1 //=-- ExprEngineObjC.cpp - ExprEngine support for Objective-C ---*- 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 file defines ExprEngine's support for Objective-C expressions.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "clang/AST/StmtObjC.h"
17 
18 using namespace clang;
19 using namespace ento;
20 
22  ExplodedNode *Pred,
23  ExplodedNodeSet &Dst) {
24  ProgramStateRef state = Pred->getState();
25  const LocationContext *LCtx = Pred->getLocationContext();
26  SVal baseVal = state->getSVal(Ex->getBase(), LCtx);
27  SVal location = state->getLValue(Ex->getDecl(), baseVal);
28 
29  ExplodedNodeSet dstIvar;
30  StmtNodeBuilder Bldr(Pred, dstIvar, *currBldrCtx);
31  Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, location));
32 
33  // Perform the post-condition check of the ObjCIvarRefExpr and store
34  // the created nodes in 'Dst'.
35  getCheckerManager().runCheckersForPostStmt(Dst, dstIvar, Ex, *this);
36 }
37 
39  ExplodedNode *Pred,
40  ExplodedNodeSet &Dst) {
41  getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this);
42 }
43 
44 /// Generate a node in \p Bldr for an iteration statement using ObjC
45 /// for-loop iterator.
47  ExplodedNodeSet &dstLocation, SValBuilder &svalBuilder,
48  const ObjCForCollectionStmt *S, const Stmt *elem, SVal elementV,
49  SymbolManager &SymMgr, const NodeBuilderContext *currBldrCtx,
50  StmtNodeBuilder &Bldr, bool hasElements) {
51 
52  for (ExplodedNode *Pred : dstLocation) {
53  ProgramStateRef state = Pred->getState();
54  const LocationContext *LCtx = Pred->getLocationContext();
55 
56  SVal hasElementsV = svalBuilder.makeTruthVal(hasElements);
57 
58  // FIXME: S is not an expression. We should not be binding values to it.
59  ProgramStateRef nextState = state->BindExpr(S, LCtx, hasElementsV);
60 
61  if (auto MV = elementV.getAs<loc::MemRegionVal>())
62  if (const auto *R = dyn_cast<TypedValueRegion>(MV->getRegion())) {
63  // FIXME: The proper thing to do is to really iterate over the
64  // container. We will do this with dispatch logic to the store.
65  // For now, just 'conjure' up a symbolic value.
66  QualType T = R->getValueType();
67  assert(Loc::isLocType(T));
68 
69  SVal V;
70  if (hasElements) {
71  SymbolRef Sym = SymMgr.conjureSymbol(elem, LCtx, T,
72  currBldrCtx->blockCount());
73  V = svalBuilder.makeLoc(Sym);
74  } else {
75  V = svalBuilder.makeIntVal(0, T);
76  }
77 
78  nextState = nextState->bindLoc(elementV, V, LCtx);
79  }
80 
81  Bldr.generateNode(S, Pred, nextState);
82  }
83 }
84 
86  ExplodedNode *Pred,
87  ExplodedNodeSet &Dst) {
88 
89  // ObjCForCollectionStmts are processed in two places. This method
90  // handles the case where an ObjCForCollectionStmt* occurs as one of the
91  // statements within a basic block. This transfer function does two things:
92  //
93  // (1) binds the next container value to 'element'. This creates a new
94  // node in the ExplodedGraph.
95  //
96  // (2) binds the value 0/1 to the ObjCForCollectionStmt* itself, indicating
97  // whether or not the container has any more elements. This value
98  // will be tested in ProcessBranch. We need to explicitly bind
99  // this value because a container can contain nil elements.
100  //
101  // FIXME: Eventually this logic should actually do dispatches to
102  // 'countByEnumeratingWithState:objects:count:' (NSFastEnumeration).
103  // This will require simulating a temporary NSFastEnumerationState, either
104  // through an SVal or through the use of MemRegions. This value can
105  // be affixed to the ObjCForCollectionStmt* instead of 0/1; when the loop
106  // terminates we reclaim the temporary (it goes out of scope) and we
107  // we can test if the SVal is 0 or if the MemRegion is null (depending
108  // on what approach we take).
109  //
110  // For now: simulate (1) by assigning either a symbol or nil if the
111  // container is empty. Thus this transfer function will by default
112  // result in state splitting.
113 
114  const Stmt *elem = S->getElement();
115  const Stmt *collection = S->getCollection();
116  ProgramStateRef state = Pred->getState();
117  SVal collectionV = state->getSVal(collection, Pred->getLocationContext());
118 
119  SVal elementV;
120  if (const auto *DS = dyn_cast<DeclStmt>(elem)) {
121  const VarDecl *elemD = cast<VarDecl>(DS->getSingleDecl());
122  assert(elemD->getInit() == nullptr);
123  elementV = state->getLValue(elemD, Pred->getLocationContext());
124  } else {
125  elementV = state->getSVal(elem, Pred->getLocationContext());
126  }
127 
128  bool isContainerNull = state->isNull(collectionV).isConstrainedTrue();
129 
130  ExplodedNodeSet dstLocation;
131  evalLocation(dstLocation, S, elem, Pred, state, elementV, false);
132 
133  ExplodedNodeSet Tmp;
134  StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx);
135 
136  if (!isContainerNull)
137  populateObjCForDestinationSet(dstLocation, svalBuilder, S, elem, elementV,
138  SymMgr, currBldrCtx, Bldr,
139  /*hasElements=*/true);
140 
141  populateObjCForDestinationSet(dstLocation, svalBuilder, S, elem, elementV,
142  SymMgr, currBldrCtx, Bldr,
143  /*hasElements=*/false);
144 
145  // Finally, run any custom checkers.
146  // FIXME: Eventually all pre- and post-checks should live in VisitStmt.
147  getCheckerManager().runCheckersForPostStmt(Dst, Tmp, S, *this);
148 }
149 
151  ExplodedNode *Pred,
152  ExplodedNodeSet &Dst) {
155  CEMgr.getObjCMethodCall(ME, Pred->getState(), Pred->getLocationContext());
156 
157  // There are three cases for the receiver:
158  // (1) it is definitely nil,
159  // (2) it is definitely non-nil, and
160  // (3) we don't know.
161  //
162  // If the receiver is definitely nil, we skip the pre/post callbacks and
163  // instead call the ObjCMessageNil callbacks and return.
164  //
165  // If the receiver is definitely non-nil, we call the pre- callbacks,
166  // evaluate the call, and call the post- callbacks.
167  //
168  // If we don't know, we drop the potential nil flow and instead
169  // continue from the assumed non-nil state as in (2). This approach
170  // intentionally drops coverage in order to prevent false alarms
171  // in the following scenario:
172  //
173  // id result = [o someMethod]
174  // if (result) {
175  // if (!o) {
176  // // <-- This program point should be unreachable because if o is nil
177  // // it must the case that result is nil as well.
178  // }
179  // }
180  //
181  // We could avoid dropping coverage by performing an explicit case split
182  // on each method call -- but this would get very expensive. An alternative
183  // would be to introduce lazy constraints.
184  // FIXME: This ignores many potential bugs (<rdar://problem/11733396>).
185  // Revisit once we have lazier constraints.
186  if (Msg->isInstanceMessage()) {
187  SVal recVal = Msg->getReceiverSVal();
188  if (!recVal.isUndef()) {
189  // Bifurcate the state into nil and non-nil ones.
190  DefinedOrUnknownSVal receiverVal =
191  recVal.castAs<DefinedOrUnknownSVal>();
192  ProgramStateRef State = Pred->getState();
193 
194  ProgramStateRef notNilState, nilState;
195  std::tie(notNilState, nilState) = State->assume(receiverVal);
196 
197  // Receiver is definitely nil, so run ObjCMessageNil callbacks and return.
198  if (nilState && !notNilState) {
199  ExplodedNodeSet dstNil;
200  StmtNodeBuilder Bldr(Pred, dstNil, *currBldrCtx);
201  bool HasTag = Pred->getLocation().getTag();
202  Pred = Bldr.generateNode(ME, Pred, nilState, nullptr,
204  assert((Pred || HasTag) && "Should have cached out already!");
205  (void)HasTag;
206  if (!Pred)
207  return;
208 
209  ExplodedNodeSet dstPostCheckers;
210  getCheckerManager().runCheckersForObjCMessageNil(dstPostCheckers, Pred,
211  *Msg, *this);
212  for (auto I : dstPostCheckers)
213  finishArgumentConstruction(Dst, I, *Msg);
214  return;
215  }
216 
217  ExplodedNodeSet dstNonNil;
218  StmtNodeBuilder Bldr(Pred, dstNonNil, *currBldrCtx);
219  // Generate a transition to the non-nil state, dropping any potential
220  // nil flow.
221  if (notNilState != State) {
222  bool HasTag = Pred->getLocation().getTag();
223  Pred = Bldr.generateNode(ME, Pred, notNilState);
224  assert((Pred || HasTag) && "Should have cached out already!");
225  (void)HasTag;
226  if (!Pred)
227  return;
228  }
229  }
230  }
231 
232  // Handle the previsits checks.
233  ExplodedNodeSet dstPrevisit;
235  *Msg, *this);
236  ExplodedNodeSet dstGenericPrevisit;
237  getCheckerManager().runCheckersForPreCall(dstGenericPrevisit, dstPrevisit,
238  *Msg, *this);
239 
240  // Proceed with evaluate the message expression.
241  ExplodedNodeSet dstEval;
242  StmtNodeBuilder Bldr(dstGenericPrevisit, dstEval, *currBldrCtx);
243 
244  for (ExplodedNodeSet::iterator DI = dstGenericPrevisit.begin(),
245  DE = dstGenericPrevisit.end(); DI != DE; ++DI) {
246  ExplodedNode *Pred = *DI;
247  ProgramStateRef State = Pred->getState();
248  CallEventRef<ObjCMethodCall> UpdatedMsg = Msg.cloneWithState(State);
249 
250  if (UpdatedMsg->isInstanceMessage()) {
251  SVal recVal = UpdatedMsg->getReceiverSVal();
252  if (!recVal.isUndef()) {
253  if (ObjCNoRet.isImplicitNoReturn(ME)) {
254  // If we raise an exception, for now treat it as a sink.
255  // Eventually we will want to handle exceptions properly.
256  Bldr.generateSink(ME, Pred, State);
257  continue;
258  }
259  }
260  } else {
261  // Check for special class methods that are known to not return
262  // and that we should treat as a sink.
263  if (ObjCNoRet.isImplicitNoReturn(ME)) {
264  // If we raise an exception, for now treat it as a sink.
265  // Eventually we will want to handle exceptions properly.
266  Bldr.generateSink(ME, Pred, Pred->getState());
267  continue;
268  }
269  }
270 
271  defaultEvalCall(Bldr, Pred, *UpdatedMsg);
272  }
273 
274  // If there were constructors called for object-type arguments, clean them up.
275  ExplodedNodeSet dstArgCleanup;
276  for (auto I : dstEval)
277  finishArgumentConstruction(dstArgCleanup, I, *Msg);
278 
279  ExplodedNodeSet dstPostvisit;
280  getCheckerManager().runCheckersForPostCall(dstPostvisit, dstArgCleanup,
281  *Msg, *this);
282 
283  // Finally, perform the post-condition check of the ObjCMessageExpr and store
284  // the created nodes in 'Dst'.
286  *Msg, *this);
287 }
A (possibly-)qualified type.
Definition: Type.h:643
Stmt - This represents one statement.
Definition: Stmt.h:66
This builder class is useful for generating nodes that resulted from visiting a statement.
Definition: CoreEngine.h:378
Manages the lifetime of CallEvent objects.
Definition: CallEvent.h:1148
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
const ProgramStateRef & getState() const
Represents a variable declaration or definition.
Definition: Decl.h:812
Defines the Objective-C statement AST node classes.
const SymExpr * SymbolRef
Definition: SymExpr.h:110
void runCheckersForObjCMessageNil(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const ObjCMethodCall &msg, ExprEngine &Eng)
Run checkers for visiting an obj-c message to nil.
LineState State
static void populateObjCForDestinationSet(ExplodedNodeSet &dstLocation, SValBuilder &svalBuilder, const ObjCForCollectionStmt *S, const Stmt *elem, SVal elementV, SymbolManager &SymMgr, const NodeBuilderContext *currBldrCtx, StmtNodeBuilder &Bldr, bool hasElements)
Generate a node in Bldr for an iteration statement using ObjC for-loop iterator.
void runCheckersForPostObjCMessage(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const ObjCMethodCall &msg, ExprEngine &Eng, bool wasInlined=false)
Run checkers for post-visiting obj-c messages.
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
static bool isLocType(QualType T)
Definition: SVals.h:329
ExplodedNode * generateSink(const Stmt *S, ExplodedNode *Pred, ProgramStateRef St, const ProgramPointTag *tag=nullptr, ProgramPoint::Kind K=ProgramPoint::PostStmtKind)
Definition: CoreEngine.h:417
void runCheckersForPreCall(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const CallEvent &Call, ExprEngine &Eng)
Run checkers for pre-visiting obj-c messages.
const LocationContext * getLocationContext() const
void runCheckersForPostCall(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const CallEvent &Call, ExprEngine &Eng, bool wasInlined=false)
Run checkers for post-visiting obj-c messages.
ObjCIvarDecl * getDecl()
Definition: ExprObjC.h:576
CheckerManager & getCheckerManager() const
Definition: ExprEngine.h:190
void runCheckersForPostStmt(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const Stmt *S, ExprEngine &Eng, bool wasInlined=false)
Run checkers for post-visiting Stmts.
void VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *DR, ExplodedNode *Pred, ExplodedNodeSet &Dst)
Transfer function logic for computing the lvalue of an Objective-C ivar.
#define V(N, I)
Definition: ASTContext.h:2913
void runCheckersForPreObjCMessage(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const ObjCMethodCall &msg, ExprEngine &Eng)
Run checkers for pre-visiting obj-c messages.
Represents Objective-C&#39;s @synchronized statement.
Definition: StmtObjC.h:277
An expression that sends a message to the given Objective-C object or class.
Definition: ExprObjC.h:950
CallEventRef< ObjCMethodCall > getObjCMethodCall(const ObjCMessageExpr *E, ProgramStateRef State, const LocationContext *LCtx)
Definition: CallEvent.h:1217
CallEventManager & getCallEventManager()
Definition: ProgramState.h:530
ProgramPoint getLocation() const
getLocation - Returns the edge associated with the given node.
SVal - This represents a symbolic expression, which can be either an L-value or an R-value...
Definition: SVals.h:75
void VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S, ExplodedNode *Pred, ExplodedNodeSet &Dst)
VisitObjCForCollectionStmt - Transfer function logic for ObjCForCollectionStmt.
void runCheckersForPreStmt(ExplodedNodeSet &Dst, const ExplodedNodeSet &Src, const Stmt *S, ExprEngine &Eng)
Run checkers for pre-visiting Stmts.
Dataflow Directional Tag Classes.
const Expr * getInit() const
Definition: Decl.h:1219
const ProgramPointTag * getTag() const
Definition: ProgramPoint.h:177
ProgramStateManager & getStateManager() override
Definition: ExprEngine.h:384
void defaultEvalCall(NodeBuilder &B, ExplodedNode *Pred, const CallEvent &Call, const EvalCallOptions &CallOpts={})
Default implementation of call evaluation.
T castAs() const
Convert to the specified SVal type, asserting that this SVal is of the desired type.
Definition: SVals.h:103
bool isImplicitNoReturn(const ObjCMessageExpr *ME)
Return true if the given message expression is known to never return.
Represents Objective-C&#39;s collection statement.
Definition: StmtObjC.h:23
void VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S, ExplodedNode *Pred, ExplodedNodeSet &Dst)
Transfer function logic for ObjCAtSynchronizedStmts.
void VisitObjCMessage(const ObjCMessageExpr *ME, ExplodedNode *Pred, ExplodedNodeSet &Dst)
const Expr * getBase() const
Definition: ExprObjC.h:580
ObjCIvarRefExpr - A reference to an ObjC instance variable.
Definition: ExprObjC.h:546
ExplodedNode * generateNode(const Stmt *S, ExplodedNode *Pred, ProgramStateRef St, const ProgramPointTag *tag=nullptr, ProgramPoint::Kind K=ProgramPoint::PostStmtKind)
Definition: CoreEngine.h:407
bool isUndef() const
Definition: SVals.h:140
CallEventRef< T > cloneWithState(ProgramStateRef State) const
Definition: CallEvent.h:82