[vhdl-200x] VHDL-2008: Records and aggregates

Hi,
I just ran into an interesting issue with VHDL-2008 aggregates.  In VHDL-2008, we allowed aggregates to effectively do concatenation when the target is an array.

Unfortunately this means you have a to_string function that is overloaded to handle records, it is now ambiguous since the record aggregate can also be interpreted as std_logic_vector.

       write (buf,  to_string( (UartRxRec.Data, UartRxRec.ErrorMode) )) ;

If you use named aggregates, this is not an impact.  However, if you do not, it may be a significant impact.

Hence, now you have to add a type qualifier.  This is an unfortunate side-effect.
       write (buf,  to_string( UartStimType'(UartRxRec.Data, UartRxRec.ErrorMode) )) ;

The original change was targeted at handling situations like:
   (CarryOut, Sum_unsigned) <= ('0' & A_unsigned) + B_unsigned ;

And also handles situations like:
   (ExtraBit, Accumulate_ufixed) <= Accumulate_ufixed + A_ufixed ;

Really wish we had allowed concatenation on the LHS instead.

We may need to look into how big of an impact this causes.

Jim

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Jim Lewis
VHDL Training Expert, SynthWorks
IEEE 1076 VHDL Working Group Chair
Open Source VHDL Verification Methodology (OSVVM), Chief Architect and Co-founder

1-503-590-4787
Jim@SynthWorks.com
http://www.SynthWorks.com

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