void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
ProgramStateRef state,
const ObjCMethodCall &Msg) const {
ASTContext &Ctx = C.getASTContext();
static CheckerProgramPointTag Tag(this, "NilReceiver");
// Check the return type of the message expression. A message to nil will
// return different values depending on the return type and the architecture.
QualType RetTy = Msg.getResultType();
CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
const LocationContext *LCtx = C.getLocationContext();
if (CanRetTy->isStructureOrClassType()) {
// Structure returns are safe since the compiler zeroes them out.
SVal V = C.getSValBuilder().makeZeroVal(RetTy);
C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
return;
}
// Other cases: check if sizeof(return type) > sizeof(void*)
if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
.isConsumedExpr(Msg.getOriginExpr())) {
// Compute: sizeof(void *) and sizeof(return type)
const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
if (CanRetTy.getTypePtr()->isReferenceType()||
(voidPtrSize < returnTypeSize &&
!(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
(Ctx.FloatTy == CanRetTy ||
Ctx.DoubleTy == CanRetTy ||
Ctx.LongDoubleTy == CanRetTy ||
Ctx.LongLongTy == CanRetTy ||
Ctx.UnsignedLongLongTy == CanRetTy)))) {
if (ExplodedNode *N = C.generateSink(state, nullptr, &Tag))
emitNilReceiverBug(C, Msg, N);
return;
}
// Handle the safe cases where the return value is 0 if the
// receiver is nil.
//
// FIXME: For now take the conservative approach that we only
// return null values if we *know* that the receiver is nil.
// This is because we can have surprises like:
//
// ... = [[NSScreens screens] objectAtIndex:0];
//
// What can happen is that [... screens] could return nil, but
// it most likely isn't nil. We should assume the semantics
// of this case unless we have *a lot* more knowledge.
//
SVal V = C.getSValBuilder().makeZeroVal(RetTy);
C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
return;
}
C.addTransition(state);
}
void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
const ProgramState *state,
ObjCMessage msg) const {
ASTContext &Ctx = C.getASTContext();
// Check the return type of the message expression. A message to nil will
// return different values depending on the return type and the architecture.
QualType RetTy = msg.getType(Ctx);
CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
if (CanRetTy->isStructureOrClassType()) {
// FIXME: At some point we shouldn't rely on isConsumedExpr(), but instead
// have the "use of undefined value" be smarter about where the
// undefined value came from.
if (C.getPredecessor()->getParentMap().isConsumedExpr(msg.getOriginExpr())){
if (ExplodedNode *N = C.generateSink(state))
emitNilReceiverBug(C, msg, N);
return;
}
// The result is not consumed by a surrounding expression. Just propagate
// the current state.
C.addTransition(state);
return;
}
// Other cases: check if the return type is smaller than void*.
if (CanRetTy != Ctx.VoidTy &&
C.getPredecessor()->getParentMap().isConsumedExpr(msg.getOriginExpr())) {
// Compute: sizeof(void *) and sizeof(return type)
const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
if (voidPtrSize < returnTypeSize &&
!(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
(Ctx.FloatTy == CanRetTy ||
Ctx.DoubleTy == CanRetTy ||
Ctx.LongDoubleTy == CanRetTy ||
Ctx.LongLongTy == CanRetTy ||
Ctx.UnsignedLongLongTy == CanRetTy))) {
if (ExplodedNode *N = C.generateSink(state))
emitNilReceiverBug(C, msg, N);
return;
}
// Handle the safe cases where the return value is 0 if the
// receiver is nil.
//
// FIXME: For now take the conservative approach that we only
// return null values if we *know* that the receiver is nil.
// This is because we can have surprises like:
//
// ... = [[NSScreens screens] objectAtIndex:0];
//
// What can happen is that [... screens] could return nil, but
// it most likely isn't nil. We should assume the semantics
// of this case unless we have *a lot* more knowledge.
//
SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
C.generateNode(state->BindExpr(msg.getOriginExpr(), V));
return;
}
C.addTransition(state);
}