System-call implementations do not handle format values

We’ve overloaded $error etc to allow us to provide a consistent logging mechanism.

Unfortunately this implementation doesn’t handle format values appropriately.

[eric-wieser]

We might have to port the extremely heavyweight implementation of get_display from iverilog:

https://github.com/steveicarus/iverilog/blob/9d0d1938dc66b715b1ac6693913a9e79d3cb401c/vpi/sys_display.c#L960-L1137

@pgfarley I think your last point is a non-issue, it can be solved with code like:

// this doesn't use C varargs, but VPI iteration
char *str = format_using_verilog_semantics(args_from_vpi);

// no formatting or varargs needed here
gpi_log(..., "%s", str);

free(str);

[pgfarley]

It looks to me like this is unfortunately going to be a more involved fix than handling the arguments over to vasprintf .

Issues:

• verilog $display type functions support verilog specific format characters like %m (hierarchical name) and and %T (simulation time).
• As part of iterating over the vpiArgument we’ll need to do the same Verilog to C type conversion of the arguments that a simulator would have to do.
• It’s not obvious to me how we can get the runtime iterated arguments into va_list to hand off for formatting.

So I think we’ll need to implement the string interpolation/formatting ourselves similar to what a simulator would do if it were handling the call to $info, $error, etc.

I can work on this but, as it’s a non trivial amount of new code, I wanted to run it by the list to see if anyone had a better idea.