ExprEngineObjC.cpp revision dc84cd5efdd3430efb22546b4ac656aa0540b210 
1//=-- ExprEngineObjC.cpp - ExprEngine support for Objective-C ---*- 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 file defines ExprEngine's support for Objective-C expressions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/AST/StmtObjC.h"
15#include "clang/StaticAnalyzer/Core/CheckerManager.h"
16#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
17#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
18
19using namespace clang;
20using namespace ento;
21
22void ExprEngine::VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *Ex,
23                                          ExplodedNode *Pred,
24                                          ExplodedNodeSet &Dst) {
25  ProgramStateRef state = Pred->getState();
26  const LocationContext *LCtx = Pred->getLocationContext();
27  SVal baseVal = state->getSVal(Ex->getBase(), LCtx);
28  SVal location = state->getLValue(Ex->getDecl(), baseVal);
29
30  ExplodedNodeSet dstIvar;
31  StmtNodeBuilder Bldr(Pred, dstIvar, *currBldrCtx);
32  Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, location));
33
34  // Perform the post-condition check of the ObjCIvarRefExpr and store
35  // the created nodes in 'Dst'.
36  getCheckerManager().runCheckersForPostStmt(Dst, dstIvar, Ex, *this);
37}
38
39void ExprEngine::VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S,
40                                             ExplodedNode *Pred,
41                                             ExplodedNodeSet &Dst) {
42  getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this);
43}
44
45void ExprEngine::VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S,
46                                            ExplodedNode *Pred,
47                                            ExplodedNodeSet &Dst) {
48
49  // ObjCForCollectionStmts are processed in two places.  This method
50  // handles the case where an ObjCForCollectionStmt* occurs as one of the
51  // statements within a basic block.  This transfer function does two things:
52  //
53  //  (1) binds the next container value to 'element'.  This creates a new
54  //      node in the ExplodedGraph.
55  //
56  //  (2) binds the value 0/1 to the ObjCForCollectionStmt* itself, indicating
57  //      whether or not the container has any more elements.  This value
58  //      will be tested in ProcessBranch.  We need to explicitly bind
59  //      this value because a container can contain nil elements.
60  //
61  // FIXME: Eventually this logic should actually do dispatches to
62  //   'countByEnumeratingWithState:objects:count:' (NSFastEnumeration).
63  //   This will require simulating a temporary NSFastEnumerationState, either
64  //   through an SVal or through the use of MemRegions.  This value can
65  //   be affixed to the ObjCForCollectionStmt* instead of 0/1; when the loop
66  //   terminates we reclaim the temporary (it goes out of scope) and we
67  //   we can test if the SVal is 0 or if the MemRegion is null (depending
68  //   on what approach we take).
69  //
70  //  For now: simulate (1) by assigning either a symbol or nil if the
71  //    container is empty.  Thus this transfer function will by default
72  //    result in state splitting.
73
74  const Stmt *elem = S->getElement();
75  ProgramStateRef state = Pred->getState();
76  SVal elementV;
77
78  if (const DeclStmt *DS = dyn_cast<DeclStmt>(elem)) {
79    const VarDecl *elemD = cast<VarDecl>(DS->getSingleDecl());
80    assert(elemD->getInit() == 0);
81    elementV = state->getLValue(elemD, Pred->getLocationContext());
82  }
83  else {
84    elementV = state->getSVal(elem, Pred->getLocationContext());
85  }
86
87  ExplodedNodeSet dstLocation;
88  evalLocation(dstLocation, S, elem, Pred, state, elementV, NULL, false);
89
90  ExplodedNodeSet Tmp;
91  StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx);
92
93  for (ExplodedNodeSet::iterator NI = dstLocation.begin(),
94       NE = dstLocation.end(); NI!=NE; ++NI) {
95    Pred = *NI;
96    ProgramStateRef state = Pred->getState();
97    const LocationContext *LCtx = Pred->getLocationContext();
98
99    // Handle the case where the container still has elements.
100    SVal TrueV = svalBuilder.makeTruthVal(1);
101    ProgramStateRef hasElems = state->BindExpr(S, LCtx, TrueV);
102
103    // Handle the case where the container has no elements.
104    SVal FalseV = svalBuilder.makeTruthVal(0);
105    ProgramStateRef noElems = state->BindExpr(S, LCtx, FalseV);
106
107    if (Optional<loc::MemRegionVal> MV = elementV.getAs<loc::MemRegionVal>())
108      if (const TypedValueRegion *R =
109          dyn_cast<TypedValueRegion>(MV->getRegion())) {
110        // FIXME: The proper thing to do is to really iterate over the
111        //  container.  We will do this with dispatch logic to the store.
112        //  For now, just 'conjure' up a symbolic value.
113        QualType T = R->getValueType();
114        assert(Loc::isLocType(T));
115        SymbolRef Sym = SymMgr.conjureSymbol(elem, LCtx, T,
116                                             currBldrCtx->blockCount());
117        SVal V = svalBuilder.makeLoc(Sym);
118        hasElems = hasElems->bindLoc(elementV, V);
119
120        // Bind the location to 'nil' on the false branch.
121        SVal nilV = svalBuilder.makeIntVal(0, T);
122        noElems = noElems->bindLoc(elementV, nilV);
123      }
124
125    // Create the new nodes.
126    Bldr.generateNode(S, Pred, hasElems);
127    Bldr.generateNode(S, Pred, noElems);
128  }
129
130  // Finally, run any custom checkers.
131  // FIXME: Eventually all pre- and post-checks should live in VisitStmt.
132  getCheckerManager().runCheckersForPostStmt(Dst, Tmp, S, *this);
133}
134
135void ExprEngine::VisitObjCMessage(const ObjCMessageExpr *ME,
136                                  ExplodedNode *Pred,
137                                  ExplodedNodeSet &Dst) {
138  CallEventManager &CEMgr = getStateManager().getCallEventManager();
139  CallEventRef<ObjCMethodCall> Msg =
140    CEMgr.getObjCMethodCall(ME, Pred->getState(), Pred->getLocationContext());
141
142  // Handle the previsits checks.
143  ExplodedNodeSet dstPrevisit;
144  getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred,
145                                                   *Msg, *this);
146  ExplodedNodeSet dstGenericPrevisit;
147  getCheckerManager().runCheckersForPreCall(dstGenericPrevisit, dstPrevisit,
148                                            *Msg, *this);
149
150  // Proceed with evaluate the message expression.
151  ExplodedNodeSet dstEval;
152  StmtNodeBuilder Bldr(dstGenericPrevisit, dstEval, *currBldrCtx);
153
154  for (ExplodedNodeSet::iterator DI = dstGenericPrevisit.begin(),
155       DE = dstGenericPrevisit.end(); DI != DE; ++DI) {
156    ExplodedNode *Pred = *DI;
157    ProgramStateRef State = Pred->getState();
158    CallEventRef<ObjCMethodCall> UpdatedMsg = Msg.cloneWithState(State);
159
160    if (UpdatedMsg->isInstanceMessage()) {
161      SVal recVal = UpdatedMsg->getReceiverSVal();
162      if (!recVal.isUndef()) {
163        // Bifurcate the state into nil and non-nil ones.
164        DefinedOrUnknownSVal receiverVal =
165            recVal.castAs<DefinedOrUnknownSVal>();
166
167        ProgramStateRef notNilState, nilState;
168        llvm::tie(notNilState, nilState) = State->assume(receiverVal);
169
170        // There are three cases: can be nil or non-nil, must be nil, must be
171        // non-nil. We ignore must be nil, and merge the rest two into non-nil.
172        // FIXME: This ignores many potential bugs (<rdar://problem/11733396>).
173        // Revisit once we have lazier constraints.
174        if (nilState && !notNilState) {
175          continue;
176        }
177
178        // Check if the "raise" message was sent.
179        assert(notNilState);
180        if (ObjCNoRet.isImplicitNoReturn(ME)) {
181          // If we raise an exception, for now treat it as a sink.
182          // Eventually we will want to handle exceptions properly.
183          Bldr.generateSink(ME, Pred, State);
184          continue;
185        }
186
187        // Generate a transition to non-Nil state.
188        if (notNilState != State) {
189          Pred = Bldr.generateNode(ME, Pred, notNilState);
190          assert(Pred && "Should have cached out already!");
191        }
192      }
193    } else {
194      // Check for special class methods that are known to not return
195      // and that we should treat as a sink.
196      if (ObjCNoRet.isImplicitNoReturn(ME)) {
197        // If we raise an exception, for now treat it as a sink.
198        // Eventually we will want to handle exceptions properly.
199        Bldr.generateSink(ME, Pred, Pred->getState());
200        continue;
201      }
202    }
203
204    defaultEvalCall(Bldr, Pred, *UpdatedMsg);
205  }
206
207  ExplodedNodeSet dstPostvisit;
208  getCheckerManager().runCheckersForPostCall(dstPostvisit, dstEval,
209                                             *Msg, *this);
210
211  // Finally, perform the post-condition check of the ObjCMessageExpr and store
212  // the created nodes in 'Dst'.
213  getCheckerManager().runCheckersForPostObjCMessage(Dst, dstPostvisit,
214                                                    *Msg, *this);
215}
216