strong typing and SC

From: John Shields <John_Shields_at_.....>
Date: Wed Jun 27 2007 - 11:36:41 PDT
Hi,

There was a statement in the unapproved minutes of 6/13 that suggested that between SV or VHDL and SC, one cannot have the "same type" because the definition has to exist in 2 places, i.e., in HDL as well as a C++ header file.  Of course this is an implementation truth, but the requirement is not weakened and nor is the semantic concept of same type. I can still define the semantic equivalence rules necessary to have a single source for a shared type definition. Again, your implementation mileage may vary, but I can translate that definition to its equivalent definition between HDL and SC automatically and rebuild code and recompile HDL automatically, too. At the other end of the implementation spectrum, I may require the HDL and SC header to be both manually written and declared to be the same and require the user to keep his entire design properly up to date manually. Better tools will make less work for the users, but a good definition of what is correct is what we are aiming at, and not how to build the tools.

Under cover of the implementation, I will eventually have an HDL package and C++ header file and perhaps some mapping information that asserts the correspondence between types within them.  A user can probably always defeat the desired semantics by compiling object code with a header that is inconsistent with the associated VHDL types and still link them together.  The user has to do some work to make those kind of problems happen and ignore some aspects of what (s)he is required to do. The key point is that those actions lead to erroneous conditions and we should call them that.  The desire to achieve transparency and strong typing across SC and the HDLs must remain an important goal.

Regards, John

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