Re: [Simulavr-devel] patch #6776: No segfault on access to notimplemented I/O registers

[Dave N6NZ]

Joerg Wunsch wrote:
> > Seems reasonable to me, as doing that (accessing a non-existent
> > address or IO location) would be an error condition in the simulated
> > program. The user should be notified in an unambiguous way.
>
> OTOH, I think there's also a point for having an option where the
> simulator behaves as best as possible like real silicon, i.e. unknown
> opcodes are executed as a NOP rather than triggering an exception, and
> access to unknown storage yields unpredictable results.
Well, yes, but the point of running a simulator is to execute the 
program in an environment that provides more/richer information than the 
real hardware.  Simulators are a debug environment, and the default 
choice in case of ambiguity should always be the conservative choice, 
since that will expose the most potential bugs.  Some of those bugs can 
go unnoticed in real hardware or with "accurate" simulators.

The decision (in another mail not quoted here) to print a message that 
can be optionally silenced seems reasonable.

-dave

(Who spent way too many years developing event driven logic simulators, 
fault simulators, IDDQ-fault simulators, switch level simulators, 
behavioral simulators, RTL simulators....)