RE: [sv-champions] 5-day email vote - 1556

Shalom,

  count is initialized to -1.

  loop3 of 2nd loop is initialized to -1 and count is incremented to 0.

  loop3 of 3rd loop is initialized to 0 and count is incremented to 1.

  The initial block begins.

  The first loop executes, each time around triggering a call to
counter(). loop1 progresses through 1, 2, 3, causing count to be
incremented through 2, 3, 4, which values are printed by the first
series of $displays.

  The second loop executes with no effect on count, so each time around
it $displays 4's.

  The third loop executes, again with no effect on count, so each time
around it $displays some more 4's.

  Although according to 6.7, "Setting the initial value of a static
variable as part of the variable declaration (including static class
members) shall occur before any initial or always blocks are started.",
the LRM does not specify the execution order of static initializers.
Most implementations do these in source order.  I don't know what
happens in practice if they are in different modules, especially on
different command lines.

-- Brad

-----Original Message-----
From: Bresticker, Shalom [mailto:shalom.bresticker@intel.com] 
Sent: Tuesday, August 28, 2007 2:26 AM
To: Rich, Dave; Brad Pierce; sv-champions@eda.org
Subject: RE: [sv-champions] 5-day email vote - 1556

Hi,

Regarding 1556: 

> >         4)  The example is confusing.
> [DR] Not to me :)

I think more explanatory comments would be helpful, either as code
comments or as text before or after the example. I can figure it out,
but it takes some work. Other people might have more trouble.


> >         5)  The comments in the example are wrong, because
> they say 1
> 2
> > 3 3 3 3 3 3 3 3 should be printed, but actually it should
> be 2 3 4 4 4
> 4
> > 4 4 4
> [DR] The results assumes the illegal statement is not executed. 
> Perhaps that should be shown as a completely separate module. Would 
> that be less confusing?

I am confused, because Brad asserts that the comments say that 9 or 10
numbers should be printed, whereas I only see two comments, one says
"end // prints 1 2 3" and the other says, "end // prints 3 3 3".

Where do the other 3 or 4 come from?
I understand that there is an additional print task call. But there is
no comment saying what it will display.

And another question:
There is an initialization of int at the top of the module:
int count = -1; // static keyword not required

Afterwards, there is another initialization:
static int loop3 = counter(); // static keyword required

where
function int counter();
return count++;
endfunction

Is there something in the LRM that guarantees that the initialization of
count will occur before the initialization of loop3?

Finally, and this is not intended to suggest a modification of this
proposal, I think that 6.21 and 6.7 should xref each other, as both talk
about variable initialization. In particular, 6.21 is missing the
information about when this occurs, which is relevant in this example.

I would also cross-reference between 9.2.1, which discusses intial
procedures, and 6.7, which discusses the scheduling of variable
initialization, particularly as this is different than in 1364.

Thanks,
Shalom

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