//=-- ExprEngineObjC.cpp - ExprEngine support for Objective-C ---*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines ExprEngine's support for Objective-C expressions.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/StmtObjC.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h"
using namespace clang;
using namespace ento;
void ExprEngine::VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *Ex,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
SVal baseVal = state->getSVal(Ex->getBase(), LCtx);
SVal location = state->getLValue(Ex->getDecl(), baseVal);
ExplodedNodeSet dstIvar;
StmtNodeBuilder Bldr(Pred, dstIvar, *currentBuilderContext);
Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, location));
// Perform the post-condition check of the ObjCIvarRefExpr and store
// the created nodes in 'Dst'.
getCheckerManager().runCheckersForPostStmt(Dst, dstIvar, Ex, *this);
}
void ExprEngine::VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this);
}
void ExprEngine::VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
// ObjCForCollectionStmts are processed in two places. This method
// handles the case where an ObjCForCollectionStmt* occurs as one of the
// statements within a basic block. This transfer function does two things:
//
// (1) binds the next container value to 'element'. This creates a new
// node in the ExplodedGraph.
//
// (2) binds the value 0/1 to the ObjCForCollectionStmt* itself, indicating
// whether or not the container has any more elements. This value
// will be tested in ProcessBranch. We need to explicitly bind
// this value because a container can contain nil elements.
//
// FIXME: Eventually this logic should actually do dispatches to
// 'countByEnumeratingWithState:objects:count:' (NSFastEnumeration).
// This will require simulating a temporary NSFastEnumerationState, either
// through an SVal or through the use of MemRegions. This value can
// be affixed to the ObjCForCollectionStmt* instead of 0/1; when the loop
// terminates we reclaim the temporary (it goes out of scope) and we
// we can test if the SVal is 0 or if the MemRegion is null (depending
// on what approach we take).
//
// For now: simulate (1) by assigning either a symbol or nil if the
// container is empty. Thus this transfer function will by default
// result in state splitting.
const Stmt *elem = S->getElement();
ProgramStateRef state = Pred->getState();
SVal elementV;
StmtNodeBuilder Bldr(Pred, Dst, *currentBuilderContext);
if (const DeclStmt *DS = dyn_cast<DeclStmt>(elem)) {
const VarDecl *elemD = cast<VarDecl>(DS->getSingleDecl());
assert(elemD->getInit() == 0);
elementV = state->getLValue(elemD, Pred->getLocationContext());
}
else {
elementV = state->getSVal(elem, Pred->getLocationContext());
}
ExplodedNodeSet dstLocation;
Bldr.takeNodes(Pred);
evalLocation(dstLocation, S, elem, Pred, state, elementV, NULL, false);
Bldr.addNodes(dstLocation);
for (ExplodedNodeSet::iterator NI = dstLocation.begin(),
NE = dstLocation.end(); NI!=NE; ++NI) {
Pred = *NI;
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
// Handle the case where the container still has elements.
SVal TrueV = svalBuilder.makeTruthVal(1);
ProgramStateRef hasElems = state->BindExpr(S, LCtx, TrueV);
// Handle the case where the container has no elements.
SVal FalseV = svalBuilder.makeTruthVal(0);
ProgramStateRef noElems = state->BindExpr(S, LCtx, FalseV);
if (loc::MemRegionVal *MV = dyn_cast<loc::MemRegionVal>(&elementV))
if (const TypedValueRegion *R =
dyn_cast<TypedValueRegion>(MV->getRegion())) {
// FIXME: The proper thing to do is to really iterate over the
// container. We will do this with dispatch logic to the store.
// For now, just 'conjure' up a symbolic value.
QualType T = R->getValueType();
assert(Loc::isLocType(T));
unsigned Count = currentBuilderContext->getCurrentBlockCount();
SymbolRef Sym = SymMgr.getConjuredSymbol(elem, LCtx, T, Count);
SVal V = svalBuilder.makeLoc(Sym);
hasElems = hasElems->bindLoc(elementV, V);
// Bind the location to 'nil' on the false branch.
SVal nilV = svalBuilder.makeIntVal(0, T);
noElems = noElems->bindLoc(elementV, nilV);
}
// Create the new nodes.
Bldr.generateNode(S, Pred, hasElems);
Bldr.generateNode(S, Pred, noElems);
}
}
void ExprEngine::VisitObjCMessage(const ObjCMessage &msg,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
// Handle the previsits checks.
ExplodedNodeSet dstPrevisit;
getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred,
msg, *this);
// Proceed with evaluate the message expression.
ExplodedNodeSet dstEval;
StmtNodeBuilder Bldr(dstPrevisit, dstEval, *currentBuilderContext);
for (ExplodedNodeSet::iterator DI = dstPrevisit.begin(),
DE = dstPrevisit.end(); DI != DE; ++DI) {
ExplodedNode *Pred = *DI;
bool RaisesException = false;
if (const Expr *Receiver = msg.getInstanceReceiver()) {
ProgramStateRef state = Pred->getState();
SVal recVal = state->getSVal(Receiver, Pred->getLocationContext());
if (!recVal.isUndef()) {
// Bifurcate the state into nil and non-nil ones.
DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal);
ProgramStateRef notNilState, nilState;
llvm::tie(notNilState, nilState) = state->assume(receiverVal);
// There are three cases: can be nil or non-nil, must be nil, must be
// non-nil. We ignore must be nil, and merge the rest two into non-nil.
if (nilState && !notNilState) {
continue;
}
// Check if the "raise" message was sent.
assert(notNilState);
if (msg.getSelector() == RaiseSel)
RaisesException = true;
// If we raise an exception, for now treat it as a sink.
// Eventually we will want to handle exceptions properly.
// Dispatch to plug-in transfer function.
evalObjCMessage(Bldr, msg, Pred, notNilState, RaisesException);
}
}
else if (const ObjCInterfaceDecl *Iface = msg.getReceiverInterface()) {
IdentifierInfo* ClsName = Iface->getIdentifier();
Selector S = msg.getSelector();
// Check for special instance methods.
if (!NSExceptionII) {
ASTContext &Ctx = getContext();
NSExceptionII = &Ctx.Idents.get("NSException");
}
if (ClsName == NSExceptionII) {
enum { NUM_RAISE_SELECTORS = 2 };
// Lazily create a cache of the selectors.
if (!NSExceptionInstanceRaiseSelectors) {
ASTContext &Ctx = getContext();
NSExceptionInstanceRaiseSelectors =
new Selector[NUM_RAISE_SELECTORS];
SmallVector<IdentifierInfo*, NUM_RAISE_SELECTORS> II;
unsigned idx = 0;
// raise:format:
II.push_back(&Ctx.Idents.get("raise"));
II.push_back(&Ctx.Idents.get("format"));
NSExceptionInstanceRaiseSelectors[idx++] =
Ctx.Selectors.getSelector(II.size(), &II[0]);
// raise:format::arguments:
II.push_back(&Ctx.Idents.get("arguments"));
NSExceptionInstanceRaiseSelectors[idx++] =
Ctx.Selectors.getSelector(II.size(), &II[0]);
}
for (unsigned i = 0; i < NUM_RAISE_SELECTORS; ++i)
if (S == NSExceptionInstanceRaiseSelectors[i]) {
RaisesException = true;
break;
}
}
// If we raise an exception, for now treat it as a sink.
// Eventually we will want to handle exceptions properly.
// Dispatch to plug-in transfer function.
evalObjCMessage(Bldr, msg, Pred, Pred->getState(), RaisesException);
}
}
// Finally, perform the post-condition check of the ObjCMessageExpr and store
// the created nodes in 'Dst'.
getCheckerManager().runCheckersForPostObjCMessage(Dst, dstEval, msg, *this);
}
void ExprEngine::evalObjCMessage(StmtNodeBuilder &Bldr,
const ObjCMessage &msg,
ExplodedNode *Pred,
ProgramStateRef state,
bool GenSink) {
// First handle the return value.
SVal ReturnValue = UnknownVal();
// Some method families have known return values.
switch (msg.getMethodFamily()) {
default:
break;
case OMF_autorelease:
case OMF_retain:
case OMF_self: {
// These methods return their receivers.
const Expr *ReceiverE = msg.getInstanceReceiver();
if (ReceiverE)
ReturnValue = state->getSVal(ReceiverE, Pred->getLocationContext());
break;
}
}
// If we failed to figure out the return value, use a conjured value instead.
if (ReturnValue.isUnknown()) {
SValBuilder &SVB = getSValBuilder();
QualType ResultTy = msg.getResultType(getContext());
unsigned Count = currentBuilderContext->getCurrentBlockCount();
const Expr *CurrentE = cast<Expr>(currentStmt);
const LocationContext *LCtx = Pred->getLocationContext();
ReturnValue = SVB.getConjuredSymbolVal(NULL, CurrentE, LCtx, ResultTy, Count);
}
// Bind the return value.
const LocationContext *LCtx = Pred->getLocationContext();
state = state->BindExpr(currentStmt, LCtx, ReturnValue);
// Invalidate the arguments (and the receiver)
state = invalidateArguments(state, CallOrObjCMessage(msg, state, LCtx), LCtx);
// And create the new node.
Bldr.generateNode(msg.getMessageExpr(), Pred, state, GenSink);
assert(Bldr.hasGeneratedNodes());
}