bool OSAtomicChecker::evalOSAtomicCompareAndSwap(const CallExpr *CE,
ExprEngine &Eng,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) const {
// Not enough arguments to match OSAtomicCompareAndSwap?
if (CE->getNumArgs() != 3)
return false;
ASTContext &Ctx = Eng.getContext();
const Expr *oldValueExpr = CE->getArg(0);
QualType oldValueType = Ctx.getCanonicalType(oldValueExpr->getType());
const Expr *newValueExpr = CE->getArg(1);
QualType newValueType = Ctx.getCanonicalType(newValueExpr->getType());
// Do the types of 'oldValue' and 'newValue' match?
if (oldValueType != newValueType)
return false;
const Expr *theValueExpr = CE->getArg(2);
const PointerType *theValueType=theValueExpr->getType()->getAs<PointerType>();
// theValueType not a pointer?
if (!theValueType)
return false;
QualType theValueTypePointee =
Ctx.getCanonicalType(theValueType->getPointeeType()).getUnqualifiedType();
// The pointee must match newValueType and oldValueType.
if (theValueTypePointee != newValueType)
return false;
static SimpleProgramPointTag OSAtomicLoadTag("OSAtomicChecker : Load");
static SimpleProgramPointTag OSAtomicStoreTag("OSAtomicChecker : Store");
// Load 'theValue'.
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
ExplodedNodeSet Tmp;
SVal location = state->getSVal(theValueExpr, LCtx);
// Here we should use the value type of the region as the load type, because
// we are simulating the semantics of the function, not the semantics of
// passing argument. So the type of theValue expr is not we are loading.
// But usually the type of the varregion is not the type we want either,
// we still need to do a CastRetrievedVal in store manager. So actually this
// LoadTy specifying can be omitted. But we put it here to emphasize the
// semantics.
QualType LoadTy;
if (const TypedValueRegion *TR =
dyn_cast_or_null<TypedValueRegion>(location.getAsRegion())) {
LoadTy = TR->getValueType();
}
Eng.evalLoad(Tmp, CE, theValueExpr, Pred,
state, location, &OSAtomicLoadTag, LoadTy);
if (Tmp.empty()) {
// If no nodes were generated, other checkers must have generated sinks.
// We return an empty Dst.
return true;
}
for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end();
I != E; ++I) {
ExplodedNode *N = *I;
ProgramStateRef stateLoad = N->getState();
// Use direct bindings from the environment since we are forcing a load
// from a location that the Environment would typically not be used
// to bind a value.
SVal theValueVal_untested = stateLoad->getSVal(theValueExpr, LCtx, true);
SVal oldValueVal_untested = stateLoad->getSVal(oldValueExpr, LCtx);
// FIXME: Issue an error.
if (theValueVal_untested.isUndef() || oldValueVal_untested.isUndef()) {
return false;
}
DefinedOrUnknownSVal theValueVal =
cast<DefinedOrUnknownSVal>(theValueVal_untested);
DefinedOrUnknownSVal oldValueVal =
cast<DefinedOrUnknownSVal>(oldValueVal_untested);
SValBuilder &svalBuilder = Eng.getSValBuilder();
// Perform the comparison.
DefinedOrUnknownSVal Cmp =
svalBuilder.evalEQ(stateLoad,theValueVal,oldValueVal);
ProgramStateRef stateEqual = stateLoad->assume(Cmp, true);
// Were they equal?
if (stateEqual) {
// Perform the store.
ExplodedNodeSet TmpStore;
SVal val = stateEqual->getSVal(newValueExpr, LCtx);
// Handle implicit value casts.
if (const TypedValueRegion *R =
dyn_cast_or_null<TypedValueRegion>(location.getAsRegion())) {
val = svalBuilder.evalCast(val,R->getValueType(), newValueExpr->getType());
}
Eng.evalStore(TmpStore, CE, theValueExpr, N,
stateEqual, location, val, &OSAtomicStoreTag);
if (TmpStore.empty()) {
// If no nodes were generated, other checkers must have generated sinks.
// We return an empty Dst.
return true;
}
StmtNodeBuilder B(TmpStore, Dst, Eng.getBuilderContext());
// Now bind the result of the comparison.
for (ExplodedNodeSet::iterator I2 = TmpStore.begin(),
E2 = TmpStore.end(); I2 != E2; ++I2) {
ExplodedNode *predNew = *I2;
ProgramStateRef stateNew = predNew->getState();
// Check for 'void' return type if we have a bogus function prototype.
SVal Res = UnknownVal();
QualType T = CE->getType();
if (!T->isVoidType())
Res = Eng.getSValBuilder().makeTruthVal(true, T);
B.generateNode(CE, predNew, stateNew->BindExpr(CE, LCtx, Res), this);
}
}
// Were they not equal?
if (ProgramStateRef stateNotEqual = stateLoad->assume(Cmp, false)) {
// Check for 'void' return type if we have a bogus function prototype.
SVal Res = UnknownVal();
QualType T = CE->getType();
if (!T->isVoidType())
Res = Eng.getSValBuilder().makeTruthVal(false, CE->getType());
StmtNodeBuilder B(N, Dst, Eng.getBuilderContext());
B.generateNode(CE, N, stateNotEqual->BindExpr(CE, LCtx, Res), this);
}
}
return true;
}
void UnreachableCodeChecker::checkEndAnalysis(ExplodedGraph &G,
BugReporter &B,
ExprEngine &Eng) const {
CFGBlocksSet reachable, visited;
if (Eng.hasWorkRemaining())
return;
const Decl *D = nullptr;
CFG *C = nullptr;
ParentMap *PM = nullptr;
const LocationContext *LC = nullptr;
// Iterate over ExplodedGraph
for (ExplodedGraph::node_iterator I = G.nodes_begin(), E = G.nodes_end();
I != E; ++I) {
const ProgramPoint &P = I->getLocation();
LC = P.getLocationContext();
if (!LC->inTopFrame())
continue;
if (!D)
D = LC->getAnalysisDeclContext()->getDecl();
// Save the CFG if we don't have it already
if (!C)
C = LC->getAnalysisDeclContext()->getUnoptimizedCFG();
if (!PM)
PM = &LC->getParentMap();
if (Optional<BlockEntrance> BE = P.getAs<BlockEntrance>()) {
const CFGBlock *CB = BE->getBlock();
reachable.insert(CB->getBlockID());
}
}
// Bail out if we didn't get the CFG or the ParentMap.
if (!D || !C || !PM)
return;
// Don't do anything for template instantiations. Proving that code
// in a template instantiation is unreachable means proving that it is
// unreachable in all instantiations.
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
if (FD->isTemplateInstantiation())
return;
// Find CFGBlocks that were not covered by any node
for (CFG::const_iterator I = C->begin(), E = C->end(); I != E; ++I) {
const CFGBlock *CB = *I;
// Check if the block is unreachable
if (reachable.count(CB->getBlockID()))
continue;
// Check if the block is empty (an artificial block)
if (isEmptyCFGBlock(CB))
continue;
// Find the entry points for this block
if (!visited.count(CB->getBlockID()))
FindUnreachableEntryPoints(CB, reachable, visited);
// This block may have been pruned; check if we still want to report it
if (reachable.count(CB->getBlockID()))
continue;
// Check for false positives
if (isInvalidPath(CB, *PM))
continue;
// It is good practice to always have a "default" label in a "switch", even
// if we should never get there. It can be used to detect errors, for
// instance. Unreachable code directly under a "default" label is therefore
// likely to be a false positive.
if (const Stmt *label = CB->getLabel())
if (label->getStmtClass() == Stmt::DefaultStmtClass)
continue;
// Special case for __builtin_unreachable.
// FIXME: This should be extended to include other unreachable markers,
// such as llvm_unreachable.
if (!CB->empty()) {
bool foundUnreachable = false;
for (CFGBlock::const_iterator ci = CB->begin(), ce = CB->end();
ci != ce; ++ci) {
if (Optional<CFGStmt> S = (*ci).getAs<CFGStmt>())
if (const CallExpr *CE = dyn_cast<CallExpr>(S->getStmt())) {
if (CE->getBuiltinCallee() == Builtin::BI__builtin_unreachable ||
CE->isBuiltinAssumeFalse(Eng.getContext())) {
foundUnreachable = true;
break;
}
}
}
if (foundUnreachable)
continue;
}
// We found a block that wasn't covered - find the statement to report
SourceRange SR;
PathDiagnosticLocation DL;
SourceLocation SL;
if (const Stmt *S = getUnreachableStmt(CB)) {
// In macros, 'do {...} while (0)' is often used. Don't warn about the
// condition 0 when it is unreachable.
if (S->getBeginLoc().isMacroID())
if (const auto *I = dyn_cast<IntegerLiteral>(S))
if (I->getValue() == 0ULL)
if (const Stmt *Parent = PM->getParent(S))
if (isa<DoStmt>(Parent))
continue;
SR = S->getSourceRange();
DL = PathDiagnosticLocation::createBegin(S, B.getSourceManager(), LC);
SL = DL.asLocation();
if (SR.isInvalid() || !SL.isValid())
continue;
}
else
continue;
// Check if the SourceLocation is in a system header
const SourceManager &SM = B.getSourceManager();
if (SM.isInSystemHeader(SL) || SM.isInExternCSystemHeader(SL))
continue;
B.EmitBasicReport(D, this, "Unreachable code", "Dead code",
"This statement is never executed", DL, SR);
}
}
void ento::RegisterObjCAtSyncChecker(ExprEngine &Eng) {
// @synchronized is an Objective-C 2 feature.
if (Eng.getContext().getLangOptions().ObjC2)
Eng.registerCheck(new ObjCAtSyncChecker());
}
