[LLVMdev] Creating global data with [ 0 x ... ] type

[Scott Graham]

Hi

I'm trying to create some global data representing something similar
to a vtable in C++ (that'll be pointed to by the head of objects).
I've called this a "metadata" table below. It includes some
miscellaneous class-level information, as well as a typical vtable
list-of-function-pointers.

I need to have the vtable "inlined" into the metadata, in that I don't
want an extra indirection by storing a pointer to the vtable in the
metadata table. This means that the metadata table ends in a variable
sized array.

i.e.:

%VtableEntryType = type { i32, i32 }
%MetadataTable = type { i32, [0 x %VtableEntryType] }

However, I can't figure out how to initialize it:

; most entries elided for simplicity
@MyMetadataTable = global %MetadataTable {
	i32 0,
	[1 x %VtableEntryType] [ ; <--- problem here!
		%VtableEntryType { i32 1234, i32 1234 }
	]
}


bitcast won't let me cast from [1 x %VtableEntryType] to [0 x
%VtableEntryType] (I guess because the size differs). Is there another
way to accomplish this initialization?

I currently have a different metadata-type per language-type, but when
there's 50k types in the system, it gets overly heavy to declare all
those types when the only thing that ever happens to @MyMetadataTable
is a store into the header of an object during allocation.

thanks,
scott