In reply to HemantP_8236:
Would $bits( UN_A ) work?
i.e.
localparam SIZE_UN_A = $bits( UN_A )
I don’t know all the rules for unions. I think packed unions should work; tagged unions have other rules (allowing dynamic types) - but then you made UN_B taggged and packed…
I’m actually not sure here, but it should be a quick test.