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Make packages easier to test

Is your capability/feature request related to a problem?

When writing tests for the standard VHDL packages things are very much complicated by two things:

  1. The packages are assumed to be compiled into a library named ieee. For example, numeric_std.vhdl is doing
use IEEE.STD_LOGIC_1164.all;

No simulator I've tested allow that you recompile the libraries in ieee so in order to verify a new feature the current VUnit script uses a preprocessor to replace all references to ieee with new_ieee such that the code can be verified in another namespace. It works but it's an extra complicating step and I think idiomatic use of VHDL is to use work.

  1. The standard packages are not self-contained. Here's an example from std_logic_1164.vhd 
  -- the following operations are predefined

  --  function "?=" (l, r : STD_ULOGIC) return STD_ULOGIC;
  --  function "?=" (l, r : STD_ULOGIC_VECTOR) return STD_ULOGIC;

  --  function "?/=" (l, r : STD_ULOGIC) return STD_ULOGIC;
  --  function "?/=" (l, r : STD_ULOGIC_VECTOR) return STD_ULOGIC;

  --  function "?<" (l, r  : STD_ULOGIC) return STD_ULOGIC;
  --  function "?<=" (l, r : STD_ULOGIC) return STD_ULOGIC;
  --  function "?>" (l, r  : STD_ULOGIC) return STD_ULOGIC;
  --  function "?>=" (l, r : STD_ULOGIC) return STD_ULOGIC;

The VUnit preprocessor cannot replace references to ieee.std_logic_1164 with new_ieee.std_logic_1164 because if std_logic_1164 is compiled into new_ieee some function definitions will be missing. For that reason the original std_logic_1164 must be used. That works today but what if we want to test updates to std_logic_1164?

Describe the solution you'd like

  1. Replace all references to ieee with work. In that way the tested code can be compiled into any namespace without being modified
  2. Make packages self-contained such that they can be fully tested. Note that this means that anyone can start using release candidates of these packages before they have been released or start using new releases before supported by the vendors.

Describe alternatives you've considered

The only alternative I considered is the existing work-around for our tests

Additional context

I can understand why ieee was used over work but it would be interesting to know the background for the predefined functions.