RE: [sv-bc] void casting on void function call

> "function_subroutine_call" isn't a system_tf_call

According to A.8.2 --

   function_subroutine_call --> subroutine_call --> system_tf_call

-- Brad

-----Original Message-----
From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
Gordon Vreugdenhil
Sent: Thursday, August 30, 2007 8:28 AM
To: Surya Pratik Saha
Cc: sv-bc@eda-stds.org
Subject: Re: [sv-bc] void casting on void function call


The question is whether the intent of "function_subroutine_call"
is restricted to "function's that are expressions".  There is no real
reason to make that restriction; C for example allows void casts of void
functions as well.

If you want to argue this too narrowly, you'll argue yourself into a
bigger problem -- grammatically "function_subroutine_call"
is any call (including a task).  The semantic intent is in the
"function" prefix.  But "function_subroutine_call" isn't a
system_tf_call so one could argue that void'($bits(x)) would be illegal.
Clearly that isn't the intent once you consider all the systf file I/O
cases where one wants to through away return codes.

I don't see any reason to not interpret this in the most permissive way
possible.  I'd even support allowing (at least) systf task calls since
that would be a great way for real user code to insulate themselves
against possible variations in vendor implementations and/or LRM
versions.  A great example of that is with "$system" for which there is
variation in implementation.  Allowing a systask call in a void cast
would allow user code to have:
     void'($system("..."));
as completely portable code even among different vendors.

Gord

Surya Pratik Saha wrote:
> Hi,
> As per LRM-BNF, void casted statment is:
> 
> *Subroutine_call_statement ::= subroutine_call;
> | void'(function_subroutine_call);*
> 
> And for void function, LRM mentions following text (page no. 156 of 
> IEEE 1800).
> 
> *Function calls are expressions unless of type void, which are
statements:
> a = b + myfunc1(c, d); //call myfunc1 (defined above) as an expression

> myprint(a); //call myprint (defined below) as a statement function 
> void myprint (int a); ...
> endfunction
> 
> *Can **function_subroutine_call **contain void function call? I don't 
> think so, as void function call is a statement. But some simulators 
> don't think like that and passes the following case:
> 
> module top;
>     initial begin
>         void'(f());
>     end
>     function void f;
>         return ;
>     endfunction
> endmodule
> 
> Any expert comment?
> 
> --
> Regards
> Surya
> 
> 
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--
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Gordon Vreugdenhil                                503-685-0808
Model Technology (Mentor Graphics)                gordonv@model.com


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