RE: [sv-bc] Query related with default value to ref port.

In particular, the LRM also says in 13.5.2:

"Only the following shall be legal to pass by reference:
- a variable,
- a class property,
- a member of an unpacked structure, or
- an element of an unpacked array" 


It had been proposed that the LRM say something to the effect that a default causes the subroutine call to be evaluated as though the default had been specified explicitly in the call. However, this was not stated because there is a difference. An expression appearing in the subroutine call is evaluated in the context of the call, whereas a default is evaluated in the context of the subroutine declaration.

Steven's statements that "the default must be a legal value to use as the actual argument" and "anything that is illegal to insert would also be illegal as a default value" could be used to clarify the intent.

Shalom


> -----Original Message-----
> From: owner-sv-bc@server.eda.org 
> [mailto:owner-sv-bc@server.eda.org] On Behalf Of Steven Sharp
> Sent: Monday, July 13, 2009 8:18 PM
> To: dhiraj@cal.interrasystems.com; sv-bc@server.eda.org; 
> Dave_Rich@mentor.com
> Subject: RE: [sv-bc] Query related with default value to ref port.
> 
> 
> >From: "Rich, Dave" <Dave_Rich@mentor.com>
> 
> >Although I cannot find it in the LRM, I believe the 
> intention of a ref
> >argument is that it cannot be left unspecified. This 
> probably needs to
> >be explicitly stated.
> 
> The LRM says that defaults are allowed for ref arguments, so they can
> definitely be left unspecified.  However, the default must be a legal
> value to use as the actual argument.
> 
> 
> >> When the subroutine is called, arguments with default values can be
> >> omitted from the call, and the compiler
> >> shall insert their corresponding values.".
> 
> Therefore, anything that is illegal to insert would also be illegal as
> a default value.
> 
>  
> >> So is the following testcase is valid
> >> 
> >> task automatic TASK1(ref bit signed [6:0] in1 = -16, input signed
> >[5:0] in2,
> 
> The actual passed to a ref argument must be a variable.  You cannot
> pass -16 to a ref argument, so you cannot use it as a default.
> 
> 
> >> As most of the standard simulators are showing error for this.
> 
> As they should.
> 
> 
> Steven Sharp
> sharp@cadence.com
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