Protobuf-net deserialization exception with enum

Question

I have an enum with flags that I decorate with the [ProtoMember] attribute that serializes and deserializes fine on my local box running Win7 x64.

However my use case involves serializing on a server running Windows Server 2008 R2 Enterprise 64-bit and deserializing on my local box. When I deserialize, I get the exception:"Overflow Exception was unhandled; Arithmetic operation resulted in an overflow". It seems to be thrown from ProtoBuf.Serializers.CompiledSerializer.ProtoBuf.Serializers.IProtoSerializer.Read(Object value, ProtoReader source).

I tried changing the enum to an int and serializing on server/deserializing locally works. I would like to use the enum instead of an int. What am I doing wrong?

Not sure if this is pertinent information but the executable I run on the server is built on my local box.

The enum is from a referenced external dll. When I duplicate the enum code in my solution, deserializing works. The exception is only thrown when I am using an enum from an external dll (where I suspect the source code isn't known) and the enum value is larger than (it seems) 128. In my case, Status.Zeta and Status.All threw the exception; other enum values deserialized properly. The enum is defined as such:

[Flags]
public enum Status
{
    None = 0,
    Alpha = 1,
    Beta = 8,
    Gamma = 16,
    Delta = 32,
    Epsilon = 64,
    Zeta = 132,
    All = 255,
}

I cannot change the code in the dll. How can I make this work? Do I need a .proto file? I am trying to avoid this if possible.

Answer 1

This only impacts enums that are : byte

D'oh! Spot the brain-dead error:

case ProtoTypeCode.SByte: Emit(OpCodes.Conv_Ovf_U1); break;
case ProtoTypeCode.Byte: Emit(OpCodes.Conv_Ovf_I1); break;

This will be reversed and deployed later today. Thanks.

To explain properly: byte is unsigned (0 to 255), sbyte is signed (-128 to 127); Conv_Ovf_U1 is basically IL for "convert to byte, checking for overflow" (like how the checked keyword in C# works), and Conv_Ovf_I1 is "convert to sbyte, checking for overflow". Hence any value over 127 was triggering the overflow flag, causing an exception. This is fixed in r614, now deployed.

Answer 2

That is indeed a bit strange. There could be differences in the CLR that affect ProtoBuf (for instance, the CLR ships with a number of different GCs). Comparing the Machine.config files from the two machines might expose some differences.

As for solving the problem, you could try marking the enum itself with ProtoContract and each enum member with ProtoMember. The latter allows you to set a Value property for ProtoBuf to use. You can also set the DataFormat to Fixed and see if that works better than the default.

You can find some examples here.