Basic type: unknown & void

BT_UNK and BT_VOID with non-zero type flags can be used in function (and struct) declarations to describe the function arguments or structure fields if only their size is known. They may be used in ida to describe the user input.

In general BT_... bits should not be used alone to describe types. Use BTF_... constants instead.

For struct used also as 'single-field-alignment-suffix' [__declspec(align(x))] with TYPE_MODIF_MASK == TYPE_FULL_MASK.