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//=-- ExprEngineCallAndReturn.cpp - Support for call/return -----*- 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 calls and returns.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h"
#include "clang/AST/DeclCXX.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Support/SaveAndRestore.h"
using namespace clang;
using namespace ento;
void ExprEngine::processCallEnter(CallEnter CE, ExplodedNode *Pred) {
// Get the entry block in the CFG of the callee.
const StackFrameContext *calleeCtx = CE.getCalleeContext();
const CFG *CalleeCFG = calleeCtx->getCFG();
const CFGBlock *Entry = &(CalleeCFG->getEntry());
// Validate the CFG.
assert(Entry->empty());
assert(Entry->succ_size() == 1);
// Get the solitary sucessor.
const CFGBlock *Succ = *(Entry->succ_begin());
// Construct an edge representing the starting location in the callee.
BlockEdge Loc(Entry, Succ, calleeCtx);
// Construct a new state which contains the mapping from actual to
// formal arguments.
const LocationContext *callerCtx = Pred->getLocationContext();
ProgramStateRef state = Pred->getState()->enterStackFrame(callerCtx,
calleeCtx);
// Construct a new node and add it to the worklist.
bool isNew;
ExplodedNode *Node = G.getNode(Loc, state, false, &isNew);
Node->addPredecessor(Pred, G);
if (isNew)
Engine.getWorkList()->enqueue(Node);
}
static const ReturnStmt *getReturnStmt(const ExplodedNode *Node) {
while (Node) {
const ProgramPoint &PP = Node->getLocation();
// Skip any BlockEdges.
if (isa<BlockEdge>(PP) || isa<CallExit>(PP)) {
assert(Node->pred_size() == 1);
Node = *Node->pred_begin();
continue;
}
if (const StmtPoint *SP = dyn_cast<StmtPoint>(&PP)) {
const Stmt *S = SP->getStmt();
return dyn_cast<ReturnStmt>(S);
}
break;
}
return 0;
}
void ExprEngine::processCallExit(ExplodedNode *Pred) {
ProgramStateRef state = Pred->getState();
const StackFrameContext *calleeCtx =
Pred->getLocationContext()->getCurrentStackFrame();
const LocationContext *callerCtx = calleeCtx->getParent();
const Stmt *CE = calleeCtx->getCallSite();
// If the callee returns an expression, bind its value to CallExpr.
if (const ReturnStmt *RS = getReturnStmt(Pred)) {
const LocationContext *LCtx = Pred->getLocationContext();
SVal V = state->getSVal(RS, LCtx);
state = state->BindExpr(CE, callerCtx, V);
}
// Bind the constructed object value to CXXConstructExpr.
if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(CE)) {
const CXXThisRegion *ThisR =
getCXXThisRegion(CCE->getConstructor()->getParent(), calleeCtx);
SVal ThisV = state->getSVal(ThisR);
// Always bind the region to the CXXConstructExpr.
state = state->BindExpr(CCE, Pred->getLocationContext(), ThisV);
}
static SimpleProgramPointTag returnTag("ExprEngine : Call Return");
PostStmt Loc(CE, callerCtx, &returnTag);
bool isNew;
ExplodedNode *N = G.getNode(Loc, state, false, &isNew);
N->addPredecessor(Pred, G);
if (!isNew)
return;
// Perform the post-condition check of the CallExpr.
ExplodedNodeSet Dst;
NodeBuilderContext Ctx(Engine, calleeCtx->getCallSiteBlock(), N);
SaveAndRestore<const NodeBuilderContext*> NBCSave(currentBuilderContext,
&Ctx);
SaveAndRestore<unsigned> CBISave(currentStmtIdx, calleeCtx->getIndex());
getCheckerManager().runCheckersForPostStmt(Dst, N, CE, *this,
/* wasInlined */ true);
// Enqueue the next element in the block.
for (ExplodedNodeSet::iterator I = Dst.begin(), E = Dst.end(); I != E; ++I) {
Engine.getWorkList()->enqueue(*I,
calleeCtx->getCallSiteBlock(),
calleeCtx->getIndex()+1);
}
}
static unsigned getNumberStackFrames(const LocationContext *LCtx) {
unsigned count = 0;
while (LCtx) {
if (isa<StackFrameContext>(LCtx))
++count;
LCtx = LCtx->getParent();
}
return count;
}
// Determine if we should inline the call.
bool ExprEngine::shouldInlineDecl(const FunctionDecl *FD, ExplodedNode *Pred) {
AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(FD);
const CFG *CalleeCFG = CalleeADC->getCFG();
if (getNumberStackFrames(Pred->getLocationContext())
== AMgr.InlineMaxStackDepth)
return false;
if (Engine.FunctionSummaries->hasReachedMaxBlockCount(FD))
return false;
if (CalleeCFG->getNumBlockIDs() > AMgr.InlineMaxFunctionSize)
return false;
return true;
}
// For now, skip inlining variadic functions.
// We also don't inline blocks.
static bool shouldInlineCallExpr(const CallExpr *CE, ExprEngine *E) {
if (!E->getAnalysisManager().shouldInlineCall())
return false;
QualType callee = CE->getCallee()->getType();
const FunctionProtoType *FT = 0;
if (const PointerType *PT = callee->getAs<PointerType>())
FT = dyn_cast<FunctionProtoType>(PT->getPointeeType());
else if (const BlockPointerType *BT = callee->getAs<BlockPointerType>()) {
// FIXME: inline blocks.
// FT = dyn_cast<FunctionProtoType>(BT->getPointeeType());
(void) BT;
return false;
}
// If we have no prototype, assume the function is okay.
if (!FT)
return true;
// Skip inlining of variadic functions.
return !FT->isVariadic();
}
bool ExprEngine::InlineCall(ExplodedNodeSet &Dst,
const CallExpr *CE,
ExplodedNode *Pred) {
if (!shouldInlineCallExpr(CE, this))
return false;
ProgramStateRef state = Pred->getState();
const Expr *Callee = CE->getCallee();
const FunctionDecl *FD =
state->getSVal(Callee, Pred->getLocationContext()).getAsFunctionDecl();
if (!FD || !FD->hasBody(FD))
return false;
switch (CE->getStmtClass()) {
default:
// FIXME: Handle C++.
break;
case Stmt::CallExprClass: {
if (!shouldInlineDecl(FD, Pred))
return false;
// Construct a new stack frame for the callee.
AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(FD);
const StackFrameContext *CallerSFC =
Pred->getLocationContext()->getCurrentStackFrame();
const StackFrameContext *CalleeSFC =
CalleeADC->getStackFrame(CallerSFC, CE,
currentBuilderContext->getBlock(),
currentStmtIdx);
CallEnter Loc(CE, CalleeSFC, Pred->getLocationContext());
bool isNew;
if (ExplodedNode *N = G.getNode(Loc, state, false, &isNew)) {
N->addPredecessor(Pred, G);
if (isNew)
Engine.getWorkList()->enqueue(N);
}
return true;
}
}
return false;
}
static bool isPointerToConst(const ParmVarDecl *ParamDecl) {
QualType PointeeTy = ParamDecl->getOriginalType()->getPointeeType();
if (PointeeTy != QualType() && PointeeTy.isConstQualified() &&
!PointeeTy->isAnyPointerType() && !PointeeTy->isReferenceType()) {
return true;
}
return false;
}
// Try to retrieve the function declaration and find the function parameter
// types which are pointers/references to a non-pointer const.
// We do not invalidate the corresponding argument regions.
static void findPtrToConstParams(llvm::SmallSet<unsigned, 1> &PreserveArgs,
const CallOrObjCMessage &Call) {
const Decl *CallDecl = Call.getDecl();
if (!CallDecl)
return;
if (const FunctionDecl *FDecl = dyn_cast<FunctionDecl>(CallDecl)) {
const IdentifierInfo *II = FDecl->getIdentifier();
// List the cases, where the region should be invalidated even if the
// argument is const.
if (II) {
StringRef FName = II->getName();
// - 'int pthread_setspecific(ptheread_key k, const void *)' stores a
// value into thread local storage. The value can later be retrieved with
// 'void *ptheread_getspecific(pthread_key)'. So even thought the
// parameter is 'const void *', the region escapes through the call.
// - funopen - sets a buffer for future IO calls.
// - ObjC functions that end with "NoCopy" can free memory, of the passed
// in buffer.
// - Many CF containers allow objects to escape through custom
// allocators/deallocators upon container construction.
// - NSXXInsertXX, for example NSMapInsertIfAbsent, since they can
// be deallocated by NSMapRemove.
if (FName == "pthread_setspecific" ||
FName == "funopen" ||
FName.endswith("NoCopy") ||
(FName.startswith("NS") &&
(FName.find("Insert") != StringRef::npos)) ||
Call.isCFCGAllowingEscape(FName))
return;
}
for (unsigned Idx = 0, E = Call.getNumArgs(); Idx != E; ++Idx) {
if (FDecl && Idx < FDecl->getNumParams()) {
if (isPointerToConst(FDecl->getParamDecl(Idx)))
PreserveArgs.insert(Idx);
}
}
return;
}
if (const ObjCMethodDecl *MDecl = dyn_cast<ObjCMethodDecl>(CallDecl)) {
assert(MDecl->param_size() <= Call.getNumArgs());
unsigned Idx = 0;
for (clang::ObjCMethodDecl::param_const_iterator
I = MDecl->param_begin(), E = MDecl->param_end(); I != E; ++I, ++Idx) {
if (isPointerToConst(*I))
PreserveArgs.insert(Idx);
}
return;
}
}
ProgramStateRef
ExprEngine::invalidateArguments(ProgramStateRef State,
const CallOrObjCMessage &Call,
const LocationContext *LC) {
SmallVector<const MemRegion *, 8> RegionsToInvalidate;
if (Call.isObjCMessage()) {
// Invalidate all instance variables of the receiver of an ObjC message.
// FIXME: We should be able to do better with inter-procedural analysis.
if (const MemRegion *MR = Call.getInstanceMessageReceiver(LC).getAsRegion())
RegionsToInvalidate.push_back(MR);
} else if (Call.isCXXCall()) {
// Invalidate all instance variables for the callee of a C++ method call.
// FIXME: We should be able to do better with inter-procedural analysis.
// FIXME: We can probably do better for const versus non-const methods.
if (const MemRegion *Callee = Call.getCXXCallee().getAsRegion())
RegionsToInvalidate.push_back(Callee);
} else if (Call.isFunctionCall()) {
// Block calls invalidate all captured-by-reference values.
SVal CalleeVal = Call.getFunctionCallee();
if (const MemRegion *Callee = CalleeVal.getAsRegion()) {
if (isa<BlockDataRegion>(Callee))
RegionsToInvalidate.push_back(Callee);
}
}
// Indexes of arguments whose values will be preserved by the call.
llvm::SmallSet<unsigned, 1> PreserveArgs;
findPtrToConstParams(PreserveArgs, Call);
for (unsigned idx = 0, e = Call.getNumArgs(); idx != e; ++idx) {
if (PreserveArgs.count(idx))
continue;
SVal V = Call.getArgSVal(idx);
// If we are passing a location wrapped as an integer, unwrap it and
// invalidate the values referred by the location.
if (nonloc::LocAsInteger *Wrapped = dyn_cast<nonloc::LocAsInteger>(&V))
V = Wrapped->getLoc();
else if (!isa<Loc>(V))
continue;
if (const MemRegion *R = V.getAsRegion()) {
// Invalidate the value of the variable passed by reference.
// Are we dealing with an ElementRegion? If the element type is
// a basic integer type (e.g., char, int) and the underlying region
// is a variable region then strip off the ElementRegion.
// FIXME: We really need to think about this for the general case
// as sometimes we are reasoning about arrays and other times
// about (char*), etc., is just a form of passing raw bytes.
// e.g., void *p = alloca(); foo((char*)p);
if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) {
// Checking for 'integral type' is probably too promiscuous, but
// we'll leave it in for now until we have a systematic way of
// handling all of these cases. Eventually we need to come up
// with an interface to StoreManager so that this logic can be
// appropriately delegated to the respective StoreManagers while
// still allowing us to do checker-specific logic (e.g.,
// invalidating reference counts), probably via callbacks.
if (ER->getElementType()->isIntegralOrEnumerationType()) {
const MemRegion *superReg = ER->getSuperRegion();
if (isa<VarRegion>(superReg) || isa<FieldRegion>(superReg) ||
isa<ObjCIvarRegion>(superReg))
R = cast<TypedRegion>(superReg);
}
// FIXME: What about layers of ElementRegions?
}
// Mark this region for invalidation. We batch invalidate regions
// below for efficiency.
RegionsToInvalidate.push_back(R);
} else {
// Nuke all other arguments passed by reference.
// FIXME: is this necessary or correct? This handles the non-Region
// cases. Is it ever valid to store to these?
State = State->unbindLoc(cast<Loc>(V));
}
}
// Invalidate designated regions using the batch invalidation API.
// FIXME: We can have collisions on the conjured symbol if the
// expression *I also creates conjured symbols. We probably want
// to identify conjured symbols by an expression pair: the enclosing
// expression (the context) and the expression itself. This should
// disambiguate conjured symbols.
unsigned Count = currentBuilderContext->getCurrentBlockCount();
StoreManager::InvalidatedSymbols IS;
// NOTE: Even if RegionsToInvalidate is empty, we may still invalidate
// global variables.
return State->invalidateRegions(RegionsToInvalidate,
Call.getOriginExpr(), Count, LC,
&IS, &Call);
}
static ProgramStateRef getReplayWithoutInliningState(ExplodedNode *&N,
const CallExpr *CE) {
void *ReplayState = N->getState()->get<ReplayWithoutInlining>();
if (!ReplayState)
return 0;
const CallExpr *ReplayCE = reinterpret_cast<const CallExpr*>(ReplayState);
if (CE == ReplayCE) {
return N->getState()->remove<ReplayWithoutInlining>();
}
return 0;
}
void ExprEngine::VisitCallExpr(const CallExpr *CE, ExplodedNode *Pred,
ExplodedNodeSet &dst) {
// Perform the previsit of the CallExpr.
ExplodedNodeSet dstPreVisit;
getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, CE, *this);
// Now evaluate the call itself.
class DefaultEval : public GraphExpander {
ExprEngine &Eng;
const CallExpr *CE;
public:
DefaultEval(ExprEngine &eng, const CallExpr *ce)
: Eng(eng), CE(ce) {}
virtual void expandGraph(ExplodedNodeSet &Dst, ExplodedNode *Pred) {
ProgramStateRef state = getReplayWithoutInliningState(Pred, CE);
// First, try to inline the call.
if (state == 0 && Eng.InlineCall(Dst, CE, Pred))
return;
// First handle the return value.
StmtNodeBuilder Bldr(Pred, Dst, *Eng.currentBuilderContext);
// Get the callee.
const Expr *Callee = CE->getCallee()->IgnoreParens();
if (state == 0)
state = Pred->getState();
SVal L = state->getSVal(Callee, Pred->getLocationContext());
// Figure out the result type. We do this dance to handle references.
QualType ResultTy;
if (const FunctionDecl *FD = L.getAsFunctionDecl())
ResultTy = FD->getResultType();
else
ResultTy = CE->getType();
if (CE->isLValue())
ResultTy = Eng.getContext().getPointerType(ResultTy);
// Conjure a symbol value to use as the result.
SValBuilder &SVB = Eng.getSValBuilder();
unsigned Count = Eng.currentBuilderContext->getCurrentBlockCount();
const LocationContext *LCtx = Pred->getLocationContext();
SVal RetVal = SVB.getConjuredSymbolVal(0, CE, LCtx, ResultTy, Count);
// Generate a new state with the return value set.
state = state->BindExpr(CE, LCtx, RetVal);
// Invalidate the arguments.
state = Eng.invalidateArguments(state, CallOrObjCMessage(CE, state, LCtx),
LCtx);
// And make the result node.
Bldr.generateNode(CE, Pred, state);
}
};
// Finally, evaluate the function call. We try each of the checkers
// to see if the can evaluate the function call.
ExplodedNodeSet dstCallEvaluated;
DefaultEval defEval(*this, CE);
getCheckerManager().runCheckersForEvalCall(dstCallEvaluated,
dstPreVisit,
CE, *this, &defEval);
// Finally, perform the post-condition check of the CallExpr and store
// the created nodes in 'Dst'.
getCheckerManager().runCheckersForPostStmt(dst, dstCallEvaluated, CE,
*this);
}
void ExprEngine::VisitReturnStmt(const ReturnStmt *RS, ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
ExplodedNodeSet dstPreVisit;
getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, RS, *this);
StmtNodeBuilder B(dstPreVisit, Dst, *currentBuilderContext);
if (RS->getRetValue()) {
for (ExplodedNodeSet::iterator it = dstPreVisit.begin(),
ei = dstPreVisit.end(); it != ei; ++it) {
B.generateNode(RS, *it, (*it)->getState());
}
}
}
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