/// <summary>
/// Refines the given state according to the knowledge stored in the egraph about sv
///
/// In addition, the state can be null when the knowledge is inconsistent.
/// </summary>
/// <param name="cv">symbolic value we assume to be non-null (true)</param>
/// <param name="state">state if sv is non-null (true)</param>
private static void AssumeTrue(ISymValue cv, ref NonNullState state) {
if (state == null) return;
if (state.IsNull(cv)) {
// infeasible
state = null;
return;
}
if (state.IsNonNull(cv)) return;
state.egraph[cv] = Lattice.AVal.NonNull;
foreach(EGraphTerm t in state.egraph.EqTerms(cv)) {
if (t.Function == NonNullState.EqNullId) {
ISymValue op = t.Args[0];
AssumeFalse(op, ref state);
}
if (t.Function == NonNullState.NeNullId) {
ISymValue op = t.Args[0];
AssumeTrue(op, ref state);
}
if (t.Function == NonNullState.LogicalNegId) {
ISymValue op = t.Args[0];
AssumeFalse(op, ref state);
}
if (t.Function == NonNullState.IsInstId) {
ISymValue op = t.Args[0];
AssumeTrue(op, ref state);
}
}
}
private void CheckPointerUse(Statement stat, Variable v, NonNullState nn, string purpose)
{
if (v == null) return;
if(nn.IsNull(v))
{
HandleError(stat, v, Error.UseOfNullPointer, purpose);
nn.AssignNonNull(v);
}
else if(!nn.IsNonNull(v))
{
HandleError(stat, v, Error.UseOfPossiblyNullPointer, purpose);
nn.AssumeNonNull(v);
}
}
/// <summary>
/// Refines the given state according to the knowledge stored in the egraph about sv
///
/// In addition, the state can be null when the knowledge is inconsistent.
/// </summary>
/// <param name="cv">symbolic value we assume to be null (false)</param>
private static void AssumeFalse(ISymValue cv, ref NonNullState state) {
if (state == null) return;
if (state.IsNonNull(cv)) {
// infeasible
// but we still want to go on analyzing this branch.
state = null;
return;
}
if (state.IsNull(cv)) return;
foreach(EGraphTerm t in state.egraph.EqTerms(cv)) {
if (t.Function == NonNullState.EqNullId) {
// EqNull(op) == false, therefore op != null
ISymValue op = t.Args[0];
AssumeTrue(op, ref state);
}
if (t.Function == NonNullState.NeNullId) {
// NeNull(op) == false, therefore op == null
ISymValue op = t.Args[0];
AssumeFalse(op, ref state);
}
if (t.Function == NonNullState.LogicalNegId) {
// Not(op) == false, therefore op == true
ISymValue op = t.Args[0];
AssumeTrue(op, ref state);
}
if (t.Function == NonNullState.IsInstId) {
// IsInst(op) == null, cannot deduce anything about op
}
}
// needs to be after we check EqTerms, as they verify mapping is current.
if (state != null) state.AssumeNull(cv);
}
private void CheckReceiver(Statement stat, Variable v, NonNullState nn, Node node)
{
Node offendingNode = v;
if (v == null) return;
if (v.Type.IsValueType) return;
// Create a better source context for receiver null errors.
offendingNode = new Statement(NodeType.Nop);
offendingNode.SourceContext = v.SourceContext;
// offendingNode.SourceContext.StartPos = offendingNode.SourceContext.EndPos;
// offendingNode.SourceContext.EndPos++;
if(nn.IsNull(v))
{
HandleError(stat, offendingNode, Error.ReceiverCannotBeNull, this.ts.GetTypeName(v.Type));
nn.AssignNonNull(v);
}
else if(!nn.IsNonNull(v))
{
HandleError(stat, offendingNode, Error.ReceiverMightBeNull, this.ts.GetTypeName(v.Type));
nn.AssumeNonNull(v);
}
}