Mono.Cecil does not set the HasFieldRVA field on a FieldDefinition when the InitialData property is set to non-null

[jkoritzinsky]

I'm trying to use the FieldDefinition.InitialData property to emit a static array into an image using the .data declaration feature in ECMA-335.

However, it seems that any data assigned to this field is dropped and not emitted as a .data declaration in the image.

I know that Mono.Cecil supports round-tripping the InitialData field from a loaded assembly back to disk if it hasn't been modified, but it seems that modifying it or assigning it on a new field is unsupported.

[jbevain]

Hi @jkoritzinsky,

Thank you for filing this. That definitely sounds like a bug, which might be annoying because from a quick look that should not happen:

https://github.com/jbevain/cecil/blob/master/Mono.Cecil/FieldDefinition.cs#L114
https://github.com/jbevain/cecil/blob/master/Mono.Cecil/AssemblyWriter.cs#L1595

Any chance you could start a PR with a failing test?

[jkoritzinsky]

I'll work on putting together a failing unit test for this.

[jkoritzinsky]

While putting together a unit test, I found the issue.

When a new field is created in Mono.Cecil and an array is assigned to the InitialValue field, Mono.Cecil correctly emits the value and will read it back in. However, Mono.Cecil does not set the HasFieldRVA flag, so other tools like ILDasm and ILSpy do not correctly recognize that an RVA has been assigned.

When I manually set the HasFieldRVA flag, the other tools recognize the RVA. So thankfully I have a workaround.

It would be nice if the FieldDefinition class would add that flag when the InitialData property is set. I'll update the issue title.

[jbevain]

Hah! That makes sense. Yes we should do that, should be has simple as:

		public byte [] InitialValue {
			// get
			set {
				initial_value = value;
				rva = 0;
				HasFieldRVA = !value.IsNullOrEmpty();
			}
		}

@jkoritzinsky want to send a PR with the test & the fix?

[jkoritzinsky]

Yes, I'll send a PR with a targeted test and fix.