Support for writing StandAloneSig custom attributes and custom debug info.

[ElektroKill]

Currently when reading an assembly dnlib reads a StandAloneSig into its respective class which implements IHasCustomAttribute and IHasCustomDebugInformation. However, when dnlib creates a CallingConventionSig from the StandAloneSig the custom attribute and custom debug info information is not passed over and therefore not available in the highest level model. dnlib is also unable to write custom attributes and custom debug info of StandAloneSig as seen here:

dnlib/src/DotNet/Writer/Metadata.cs

Lines 2144 to 2152 in 086cda2

	public virtual MDToken GetToken(IList<TypeSig> locals, uint origToken) {
	if (locals is null || locals.Count == 0)
	return new MDToken((Table)0, 0);
	var row = new RawStandAloneSigRow(GetSignature(new LocalSig(locals, false)));
	uint rid = tablesHeap.StandAloneSigTable.Add(row);
	//TODO: Add custom attributes
	//TODO: Add custom debug infos
	return new MDToken(Table.StandAloneSig, rid);

dnlib/src/DotNet/Writer/Metadata.cs

Lines 2161 to 2172 in 086cda2

	protected virtual uint AddStandAloneSig(MethodSig methodSig, uint origToken) {
	if (methodSig is null) {
	Error("StandAloneSig: MethodSig is null");
	return 0;
	}
	var row = new RawStandAloneSigRow(GetSignature(methodSig));
	uint rid = tablesHeap.StandAloneSigTable.Add(row);
	//TODO: Add custom attributes
	//TODO: Add custom debug infos
	return rid;
	}

dnlib/src/DotNet/Writer/Metadata.cs

Lines 2180 to 2191 in 086cda2

	protected virtual uint AddStandAloneSig(FieldSig fieldSig, uint origToken) {
	if (fieldSig is null) {
	Error("StandAloneSig: FieldSig is null");
	return 0;
	}
	var row = new RawStandAloneSigRow(GetSignature(fieldSig));
	uint rid = tablesHeap.StandAloneSigTable.Add(row);
	//TODO: Add custom attributes
	//TODO: Add custom debug infos
	return rid;
	}

[wtfsck]

Does any compiler (or other tool) attach CAs or CDIs to StandAloneSig rows?

[ElektroKill]

Hi,
To my knowledge Roslyn or other compilers do not emit custom attributes on StandAloneSig (I don’t know about custom debug infos but most likely they aren’t emitted for this table too).
However, in theory these attributes could be used to detect tampering of a file by a obfuscator since dnlib would not rewrite them but this is purely hypothetical and I’m yet to see something like this in practice.
I haven’t looked much at the signature code but I think this could be achieved in a similar way to how I handled custom attributes and custom debug infos in #418 except for LocalSig for which the Metadata class accepts a List<Local> instead of LocalSig.