1 //=-- ExprEngineObjC.cpp - ExprEngine support for Objective-C ---*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines ExprEngine's support for Objective-C expressions.
12 //===----------------------------------------------------------------------===//
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"
19 using namespace clang;
22 void ExprEngine::VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *Ex,
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);
30 ExplodedNodeSet dstIvar;
31 StmtNodeBuilder Bldr(Pred, dstIvar, *currBldrCtx);
32 Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, location));
34 // Perform the post-condition check of the ObjCIvarRefExpr and store
35 // the created nodes in 'Dst'.
36 getCheckerManager().runCheckersForPostStmt(Dst, dstIvar, Ex, *this);
39 void ExprEngine::VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S,
41 ExplodedNodeSet &Dst) {
42 getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this);
45 void ExprEngine::VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S,
47 ExplodedNodeSet &Dst) {
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:
53 // (1) binds the next container value to 'element'. This creates a new
54 // node in the ExplodedGraph.
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.
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).
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.
74 const Stmt *elem = S->getElement();
75 ProgramStateRef state = Pred->getState();
78 if (const DeclStmt *DS = dyn_cast<DeclStmt>(elem)) {
79 const VarDecl *elemD = cast<VarDecl>(DS->getSingleDecl());
80 assert(elemD->getInit() == nullptr);
81 elementV = state->getLValue(elemD, Pred->getLocationContext());
84 elementV = state->getSVal(elem, Pred->getLocationContext());
87 ExplodedNodeSet dstLocation;
88 evalLocation(dstLocation, S, elem, Pred, state, elementV, nullptr, false);
91 StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx);
93 for (ExplodedNodeSet::iterator NI = dstLocation.begin(),
94 NE = dstLocation.end(); NI!=NE; ++NI) {
96 ProgramStateRef state = Pred->getState();
97 const LocationContext *LCtx = Pred->getLocationContext();
99 // Handle the case where the container still has elements.
100 SVal TrueV = svalBuilder.makeTruthVal(1);
101 ProgramStateRef hasElems = state->BindExpr(S, LCtx, TrueV);
103 // Handle the case where the container has no elements.
104 SVal FalseV = svalBuilder.makeTruthVal(0);
105 ProgramStateRef noElems = state->BindExpr(S, LCtx, FalseV);
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);
120 // Bind the location to 'nil' on the false branch.
121 SVal nilV = svalBuilder.makeIntVal(0, T);
122 noElems = noElems->bindLoc(elementV, nilV);
125 // Create the new nodes.
126 Bldr.generateNode(S, Pred, hasElems);
127 Bldr.generateNode(S, Pred, noElems);
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);
135 void ExprEngine::VisitObjCMessage(const ObjCMessageExpr *ME,
137 ExplodedNodeSet &Dst) {
138 CallEventManager &CEMgr = getStateManager().getCallEventManager();
139 CallEventRef<ObjCMethodCall> Msg =
140 CEMgr.getObjCMethodCall(ME, Pred->getState(), Pred->getLocationContext());
142 // There are three cases for the receiver:
143 // (1) it is definitely nil,
144 // (2) it is definitely non-nil, and
145 // (3) we don't know.
147 // If the receiver is definitely nil, we skip the pre/post callbacks and
148 // instead call the ObjCMessageNil callbacks and return.
150 // If the receiver is definitely non-nil, we call the pre- callbacks,
151 // evaluate the call, and call the post- callbacks.
153 // If we don't know, we drop the potential nil flow and instead
154 // continue from the assumed non-nil state as in (2). This approach
155 // intentionally drops coverage in order to prevent false alarms
156 // in the following scenario:
158 // id result = [o someMethod]
161 // // <-- This program point should be unreachable because if o is nil
162 // // it must the case that result is nil as well.
166 // We could avoid dropping coverage by performing an explicit case split
167 // on each method call -- but this would get very expensive. An alternative
168 // would be to introduce lazy constraints.
169 // FIXME: This ignores many potential bugs (<rdar://problem/11733396>).
170 // Revisit once we have lazier constraints.
171 if (Msg->isInstanceMessage()) {
172 SVal recVal = Msg->getReceiverSVal();
173 if (!recVal.isUndef()) {
174 // Bifurcate the state into nil and non-nil ones.
175 DefinedOrUnknownSVal receiverVal =
176 recVal.castAs<DefinedOrUnknownSVal>();
177 ProgramStateRef State = Pred->getState();
179 ProgramStateRef notNilState, nilState;
180 std::tie(notNilState, nilState) = State->assume(receiverVal);
182 // Receiver is definitely nil, so run ObjCMessageNil callbacks and return.
183 if (nilState && !notNilState) {
184 StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
185 bool HasTag = Pred->getLocation().getTag();
186 Pred = Bldr.generateNode(ME, Pred, nilState, nullptr,
187 ProgramPoint::PreStmtKind);
188 assert((Pred || HasTag) && "Should have cached out already!");
192 getCheckerManager().runCheckersForObjCMessageNil(Dst, Pred,
197 ExplodedNodeSet dstNonNil;
198 StmtNodeBuilder Bldr(Pred, dstNonNil, *currBldrCtx);
199 // Generate a transition to the non-nil state, dropping any potential
201 if (notNilState != State) {
202 bool HasTag = Pred->getLocation().getTag();
203 Pred = Bldr.generateNode(ME, Pred, notNilState);
204 assert((Pred || HasTag) && "Should have cached out already!");
212 // Handle the previsits checks.
213 ExplodedNodeSet dstPrevisit;
214 getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred,
216 ExplodedNodeSet dstGenericPrevisit;
217 getCheckerManager().runCheckersForPreCall(dstGenericPrevisit, dstPrevisit,
220 // Proceed with evaluate the message expression.
221 ExplodedNodeSet dstEval;
222 StmtNodeBuilder Bldr(dstGenericPrevisit, dstEval, *currBldrCtx);
224 for (ExplodedNodeSet::iterator DI = dstGenericPrevisit.begin(),
225 DE = dstGenericPrevisit.end(); DI != DE; ++DI) {
226 ExplodedNode *Pred = *DI;
227 ProgramStateRef State = Pred->getState();
228 CallEventRef<ObjCMethodCall> UpdatedMsg = Msg.cloneWithState(State);
230 if (UpdatedMsg->isInstanceMessage()) {
231 SVal recVal = UpdatedMsg->getReceiverSVal();
232 if (!recVal.isUndef()) {
233 if (ObjCNoRet.isImplicitNoReturn(ME)) {
234 // If we raise an exception, for now treat it as a sink.
235 // Eventually we will want to handle exceptions properly.
236 Bldr.generateSink(ME, Pred, State);
241 // Check for special class methods that are known to not return
242 // and that we should treat as a sink.
243 if (ObjCNoRet.isImplicitNoReturn(ME)) {
244 // If we raise an exception, for now treat it as a sink.
245 // Eventually we will want to handle exceptions properly.
246 Bldr.generateSink(ME, Pred, Pred->getState());
251 defaultEvalCall(Bldr, Pred, *UpdatedMsg);
254 ExplodedNodeSet dstPostvisit;
255 getCheckerManager().runCheckersForPostCall(dstPostvisit, dstEval,
258 // Finally, perform the post-condition check of the ObjCMessageExpr and store
259 // the created nodes in 'Dst'.
260 getCheckerManager().runCheckersForPostObjCMessage(Dst, dstPostvisit,