Re: [myhdl-list] AttributeError in 0.8-dev but not in 0.7

[Per K. <bas...@gm...>]

Yes, I think you're right! It is mixing intbv[1:0] and bool that causes it.

If that is to be forbidden, there needs to be an assert as soon as
possible. But I don't see why we should disallow it.
The reason I didn't see it sooner was that the bool and the intbv were
instantiated in separate modules. And unless we ban one-bit intbvs or bools
outright I don't see how that sort of thing can be avoided. One hardware
designer's bool is another's one bit integer. :)
/Per

On Thu, Jan 24, 2013 at 3:08 PM, Christopher Felton
<chr...@gm...>wrote:

> On 1/24/2013 7:41 AM, Per Karlsson wrote:
> > The problem is that val is an intbv (that is checked) but next is a bool
> > (and next is never checked). So next has no ._val
> > I don't think the problem can be reproduced using mere assignments. It
> is,
> > I think, the mixed types in the conditionals that cause the error.
> > I'll make another try at reproducing it 'in vitro' once I get the time.
> > /Per
> >
> > On Thu, Jan 24, 2013 at 1:15 PM, Christopher Felton
> > <chr...@gm...>wrote:
> >
> >> The /self._val._val = next._val/ is correct, it says
> >> assign the /Signal.intbv._val/, the _val of the signal
> >> is an intbv (per the check right before).
> >>
> >
>
> Hmmm, I don't think a conditional will cause the the
> myhdl.simulator to invoke the /update/ functions.
>
> Looking at the code, I could see the attribute hazard in
> the /_update()/ function if:
>
>      _val  : type == intbv
>      _next : type == bool
>
> But for the above to occur the /Signal._SetNextVal/ would
> need to be assigned to /Signal._SetNextBool/.  Now, for that
> to occur the /Signal/ would need to be instantiated with a
> /bool/ ...
>
> Do you see the error now?  You need a complex set of
> events.  You need to create a /Signal/ of type /bool/
> then assign it to and /intbv/ and then assign it to a
> /bool/ again.  If your code inter-mixes /bool/ and
> /intbv[1:]/ a bunch there is this potential to hit this.
>
> code snip:
>
>      x = Signal(bool(0))
>      x.next = intbv(1)[1:]
>      print(type(x._val), type(x._next))
>      x._update()
>      print(type(x._val), type(x._next))
>      x.next = False
>      print(type(x._val), type(x._next))
>      x._update()
>
>
> The above will cause the error you are seeing.
>
> Now the question is, does the design intend for /bool/
> and /intbv[1:]/ interchanged.  If it does then this needs
> to be fixed, if it doesn't then we need to add an assert
> that prevents the first /intbv/ assignment to the bool.
>
> Regards,
> Chris Felton
>
>
>
>
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