// FIXME: could probably rewrite this to be more reliable using
// OpCode.StackBehaviourPop and StackBehaviourPush
//
// FIXME: This code is simply too naive to work well in the real world.
// For example, code that compares a local to null will not work
// correctly (we want the local to be null along one branch and non-
// null along the other). But this is tricky to do with the textbook
// algorithm (note that meet must be commutative). One fix is to
// splice in synthetic blocks and fix the code so that it can handle
// zero length blocks.
public void Transfer([NonNull] Node node, [NonNull] object inFact,
[NonNull] object outFact, bool warn)
{
BasicBlock bb = (BasicBlock)node;
/* Exit and exception nodes don't cover any real instructions. */
if (bb.isExit || bb.isException)
{
return;
}
//NullDerefFrame inFrame = (NullDerefFrame)inFact;
NullDerefFrame outFrame = (NullDerefFrame)outFact;
VariableDefinitionCollection vars = method.Body.Variables;
if (Verbose)
{
Trace.WriteLine(string.Empty);
Trace.WriteLine(string.Format("Basic block {0}", bb.ToString()));
Trace.WriteLine("Input frame:");
Trace.Write(outFrame.ToString());
}
for (int i = bb.first; i <= bb.last; i++)
{
Instruction insn = bb.Instructions[i];
OpCode opcode = insn.OpCode;
if (Verbose)
{
Trace.Write(string.Format(" {0}", opcode.Name));
if (insn.Operand != null && !(insn.Operand is Instruction))
{
Trace.WriteLine(string.Format(" {0}", insn.Operand.ToString()));
}
else if (insn.Operand is Instruction)
{
Trace.WriteLine(string.Format(" {0}",
((Instruction)insn.Operand).Offset.ToString("X4")));
}
else
{
Trace.WriteLine(string.Empty);
}
}
switch (opcode.Code)
{
/* Load argument */
/* Stored nullities are set to declared values on method
* entry. Starg and kin can change this over time. */
case Code.Ldarg_0:
outFrame.PushStack(outFrame.GetArgNullity(0));
break;
case Code.Ldarg_1:
outFrame.PushStack(outFrame.GetArgNullity(1));
break;
case Code.Ldarg_2:
outFrame.PushStack(outFrame.GetArgNullity(2));
break;
case Code.Ldarg_3:
outFrame.PushStack(outFrame.GetArgNullity(3));
break;
case Code.Ldarg:
if (insn.Operand is int)
{
outFrame.PushStack(outFrame.GetArgNullity((int)insn.Operand));
}
else if (insn.Operand is ParameterDefinition)
{
ParameterDefinition pd = (insn.Operand as ParameterDefinition);
outFrame.PushStack((pd.HasConstant && pd.Constant == null) ?
Nullity.Null : Nullity.NonNull);
}
else
{
outFrame.PushStack(Nullity.NonNull);
}
break;
case Code.Ldarg_S: {
ParameterDefinition param =
(ParameterDefinition)insn.Operand;
outFrame.PushStack(
outFrame.GetArgNullity(param.GetSequence() - 1));
break;
}
case Code.Ldarga:
case Code.Ldarga_S:
outFrame.PushStack(Nullity.NonNull);
break;
/* Store argument */
case Code.Starg:
outFrame.SetArgNullity((int)insn.Operand,
outFrame.PopStack());
break;
case Code.Starg_S: {
ParameterDefinition param =
(ParameterDefinition)insn.Operand;
outFrame.SetArgNullity(param.GetSequence() - 1,
outFrame.PopStack());
break;
}
/* Load local */
case Code.Ldloc_0:
outFrame.PushStack(outFrame.GetLocNullity(0));
break;
case Code.Ldloc_1:
outFrame.PushStack(outFrame.GetLocNullity(1));
break;
case Code.Ldloc_2:
outFrame.PushStack(outFrame.GetLocNullity(2));
break;
case Code.Ldloc_3:
outFrame.PushStack(outFrame.GetLocNullity(3));
break;
case Code.Ldloc:
case Code.Ldloc_S:
outFrame.PushStack(outFrame.GetLocNullity(
vars.IndexOf((VariableDefinition)insn.Operand)));
break;
case Code.Ldloca:
case Code.Ldloca_S:
outFrame.SetLocNullity(
vars.IndexOf((VariableDefinition)insn.Operand),
Nullity.Unknown);
outFrame.PushStack(Nullity.NonNull);
break;
/* Store local */
case Code.Stloc_0:
outFrame.SetLocNullity(0, outFrame.PopStack());
break;
case Code.Stloc_1:
outFrame.SetLocNullity(1, outFrame.PopStack());
break;
case Code.Stloc_2:
outFrame.SetLocNullity(2, outFrame.PopStack());
break;
case Code.Stloc_3:
outFrame.SetLocNullity(3, outFrame.PopStack());
break;
case Code.Stloc:
case Code.Stloc_S:
outFrame.SetLocNullity(
vars.IndexOf((VariableDefinition)insn.Operand),
outFrame.PopStack());
break;
/* Load other things */
case Code.Ldftn:
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Ldvirtftn:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Ldstr:
case Code.Ldnull:
outFrame.PushStack(Nullity.Null);
break;
case Code.Ldlen:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Ldtoken:
outFrame.PushStack(Nullity.NonNull);
break;
/* Object operations */
case Code.Cpobj:
outFrame.PopStack(2);
break;
case Code.Newobj:
outFrame.PopStack(
((MethodReference)insn.Operand).Parameters.Count);
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Ldobj:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Stobj:
outFrame.PopStack(2);
break;
case Code.Initobj:
outFrame.PopStack();
break;
/* Load field */
case Code.Ldfld: {
Check(insn, warn, outFrame.PopStack(), "field");
FieldReference field = (FieldReference)insn.Operand;
if (nnaCollector.HasNonNullAttribute(field))
{
outFrame.PushStack(Nullity.NonNull);
}
else
{
outFrame.PushStack(Nullity.Unknown);
}
break;
}
case Code.Ldflda:
Check(insn, warn, outFrame.PopStack(), "field");
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Ldsfld: {
FieldReference field = (FieldReference)insn.Operand;
if (nnaCollector.HasNonNullAttribute(field))
{
outFrame.PushStack(Nullity.NonNull);
}
else
{
outFrame.PushStack(Nullity.Unknown);
}
break;
}
case Code.Ldsflda:
outFrame.PushStack(Nullity.NonNull);
break;
/* Store field */
case Code.Stfld: {
/* FIXME: warn if writing null to non-null field */
Nullity n = outFrame.PopStack();
Check(insn, warn, outFrame.PopStack(), "field");
FieldReference field = (FieldReference)insn.Operand;
if (warn && nnaCollector.HasNonNullAttribute(field))
{
if (Verbose)
{
Trace.WriteLine(string.Format("FAILURE1: null deref at {0:X2}", insn.Offset));
}
if (n == Nullity.Unknown)
{
runner.Report(method, insn, Severity.High, Confidence.Low, "storing possibly null value in field declared non-null");
}
else if (n == Nullity.Null)
{
runner.Report(method, insn, Severity.High, Confidence.Low, "storing null value in field declared non-null");
}
}
break;
}
case Code.Stsfld: {
Nullity n = outFrame.PopStack();
FieldReference field = (FieldReference)insn.Operand;
if (warn && nnaCollector.HasNonNullAttribute(field))
{
if (Verbose)
{
Trace.WriteLine(string.Format("FAILURE2: null deref at {0:X2}", insn.Offset));
}
if (n == Nullity.Unknown)
{
runner.Report(method, insn, Severity.High, Confidence.Low, "storing possibly null value in field declared non-null");
}
else if (n == Nullity.Null)
{
runner.Report(method, insn, Severity.High, Confidence.Low, "storing null value in field declared non-null");
}
}
break;
}
/* Stack operations */
case Code.Dup:
outFrame.PushStack(outFrame.PeekStack());
break;
case Code.Pop:
outFrame.PopStack();
break;
/* Method call and return */
case Code.Calli:
ProcessCall(insn, warn, true, outFrame);
break;
case Code.Call:
case Code.Callvirt:
ProcessCall(insn, warn, false, outFrame);
break;
case Code.Ret:
if (!IsVoid(method.ReturnType))
{
Nullity n = outFrame.PopStack();
if (nnaCollector.HasNonNullAttribute(method) && warn)
{
if (Verbose)
{
Trace.WriteLine(string.Format("FAILURE3: null deref at {0:X2}", insn.Offset));
}
if (n == Nullity.Null)
{
runner.Report(method, insn, Severity.High, Confidence.Low, "returning null value from method declared non-null");
}
else
{
runner.Report(method, insn, Severity.High, Confidence.Low, "returning possibly null value from method declared non-null");
}
}
}
break;
/* Indirect load */
case Code.Ldind_I1:
case Code.Ldind_U1:
case Code.Ldind_I2:
case Code.Ldind_U2:
case Code.Ldind_I4:
case Code.Ldind_U4:
case Code.Ldind_I8:
case Code.Ldind_I:
case Code.Ldind_R4:
case Code.Ldind_R8:
case Code.Ldind_Ref:
outFrame.PopStack();
outFrame.PushStack(Nullity.Unknown);
break;
/* Indirect store */
case Code.Stind_Ref:
case Code.Stind_I:
case Code.Stind_I1:
case Code.Stind_I2:
case Code.Stind_I4:
case Code.Stind_I8:
case Code.Stind_R4:
case Code.Stind_R8:
outFrame.PopStack(2);
break;
/* Class-related operations */
case Code.Box:
case Code.Unbox:
case Code.Unbox_Any:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Castclass:
case Code.Isinst:
break;
/* Exception handling */
case Code.Rethrow:
case Code.Endfinally:
break;
case Code.Throw:
case Code.Endfilter:
outFrame.PopStack();
break;
case Code.Leave:
case Code.Leave_S:
outFrame.EmptyStack();
break;
/* Array operations */
case Code.Newarr:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
/* Load element */
case Code.Ldelema:
case Code.Ldelem_I1:
case Code.Ldelem_U1:
case Code.Ldelem_I2:
case Code.Ldelem_U2:
case Code.Ldelem_I4:
case Code.Ldelem_U4:
case Code.Ldelem_I8:
case Code.Ldelem_I:
case Code.Ldelem_R4:
case Code.Ldelem_R8:
outFrame.PopStack(2);
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Ldelem_Ref:
case Code.Ldelem_Any: /* This may or may not be a reference. */
outFrame.PopStack(2);
outFrame.PushStack(Nullity.Unknown);
break;
/* Store element */
/* Pop 3 */
case Code.Stelem_I:
case Code.Stelem_I1:
case Code.Stelem_I2:
case Code.Stelem_I4:
case Code.Stelem_I8:
case Code.Stelem_R4:
case Code.Stelem_R8:
case Code.Stelem_Ref:
case Code.Stelem_Any:
outFrame.PopStack(3);
break;
case Code.Arglist:
case Code.Sizeof:
outFrame.PushStack(Nullity.NonNull);
break;
case Code.Mkrefany:
case Code.Refanyval:
case Code.Refanytype:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
/* Prefixes */
case Code.Unaligned:
case Code.Volatile:
case Code.Tail:
break;
/* Effect-free instructions */
case Code.Nop:
case Code.Break:
break;
/* Load constant */
/* Push non-ref. */
case Code.Ldc_I4_M1:
case Code.Ldc_I4_0:
case Code.Ldc_I4_1:
case Code.Ldc_I4_2:
case Code.Ldc_I4_3:
case Code.Ldc_I4_4:
case Code.Ldc_I4_5:
case Code.Ldc_I4_6:
case Code.Ldc_I4_7:
case Code.Ldc_I4_8:
case Code.Ldc_I4_S:
case Code.Ldc_I4:
case Code.Ldc_I8:
case Code.Ldc_R4:
case Code.Ldc_R8:
outFrame.PushStack(Nullity.NonNull);
break;
/* Unconditional control flow */
/* Do nothing */
case Code.Br:
case Code.Br_S:
break;
/* Conditional branches */
/* Pop 1 */
case Code.Brfalse:
case Code.Brtrue:
case Code.Brfalse_S:
case Code.Brtrue_S:
outFrame.PopStack();
break;
/* Comparison branches */
/* Pop 2. */
case Code.Beq:
case Code.Bge:
case Code.Bgt:
case Code.Ble:
case Code.Blt:
case Code.Bne_Un:
case Code.Bge_Un:
case Code.Bgt_Un:
case Code.Ble_Un:
case Code.Blt_Un:
case Code.Beq_S:
case Code.Bge_S:
case Code.Bgt_S:
case Code.Ble_S:
case Code.Blt_S:
case Code.Bne_Un_S:
case Code.Bge_Un_S:
case Code.Bgt_Un_S:
case Code.Ble_Un_S:
case Code.Blt_Un_S:
outFrame.PopStack(2);
break;
case Code.Switch:
outFrame.PopStack();
break;
/* Comparisons */
/* Pop 2, push non-ref */
case Code.Ceq:
case Code.Cgt:
case Code.Cgt_Un:
case Code.Clt:
case Code.Clt_Un:
outFrame.PopStack(2);
outFrame.PushStack(Nullity.NonNull);
break;
/* Arithmetic and logical binary operators */
/* Pop 2, push non-ref */
case Code.Add:
case Code.Sub:
case Code.Mul:
case Code.Div:
case Code.Div_Un:
case Code.Rem:
case Code.Rem_Un:
case Code.And:
case Code.Or:
case Code.Xor:
case Code.Shl:
case Code.Shr:
case Code.Shr_Un:
case Code.Add_Ovf:
case Code.Add_Ovf_Un:
case Code.Mul_Ovf:
case Code.Mul_Ovf_Un:
case Code.Sub_Ovf:
case Code.Sub_Ovf_Un:
outFrame.PopStack(2);
outFrame.PushStack(Nullity.NonNull);
break;
/* Arithmetic and logical unary operators */
/* Pop 1, push non-ref */
case Code.Neg:
case Code.Not:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
/* Conversions. */
/* Do nothing. */
case Code.Conv_I1:
case Code.Conv_I2:
case Code.Conv_I4:
case Code.Conv_I8:
case Code.Conv_R4:
case Code.Conv_R8:
case Code.Conv_U4:
case Code.Conv_U8:
case Code.Conv_U:
case Code.Conv_R_Un:
case Code.Conv_Ovf_I1_Un:
case Code.Conv_Ovf_I2_Un:
case Code.Conv_Ovf_I4_Un:
case Code.Conv_Ovf_I8_Un:
case Code.Conv_Ovf_U1_Un:
case Code.Conv_Ovf_U2_Un:
case Code.Conv_Ovf_U4_Un:
case Code.Conv_Ovf_U8_Un:
case Code.Conv_Ovf_I_Un:
case Code.Conv_Ovf_U_Un:
case Code.Conv_Ovf_I1:
case Code.Conv_Ovf_U1:
case Code.Conv_Ovf_I2:
case Code.Conv_Ovf_U2:
case Code.Conv_Ovf_I4:
case Code.Conv_Ovf_U4:
case Code.Conv_Ovf_I8:
case Code.Conv_Ovf_U8:
case Code.Conv_U2:
case Code.Conv_U1:
case Code.Conv_I:
case Code.Conv_Ovf_I:
case Code.Conv_Ovf_U:
case Code.Ckfinite:
break;
/* Unverifiable instructions. */
case Code.Jmp:
break;
case Code.Cpblk:
outFrame.PopStack(3);
break;
case Code.Initblk:
outFrame.PopStack(3);
break;
case Code.Localloc:
outFrame.PopStack();
outFrame.PushStack(Nullity.NonNull);
break;
default:
Trace.WriteLine(string.Format("Unknown instruction: {0} {1}",
opcode.Name, opcode.Value.ToString("X4")));
break;
} /* switch */
} /* for */
if (Verbose)
{
Trace.WriteLine("Output frame:");
Trace.Write(outFrame.ToString());
}
} /* Transfer */
