From: Shalom Bresticker (Shalom.Bresticker@freescale.com)
Date: Mon May 03 2004 - 09:11:27 PDT
Do you people have any problem with sending your mails to email@example.com with
subject "errata/517: " ?
Charles Dawson wrote:
> Hi Jim,
> Although I agree that none of the routines have a really good description
> of what happens in erroneous situations, I think vpi_get_value() is more
> likely to be called in certain corner case situations. In these situations
> it would be good to have a more explicit description of how the routine
> should function. To me the most interesting ones are:
> - When simulation has not yet begun, what is the value of an object that
> you would otherwise normally be able to get a value for?
> - Similarly, when simulation has completed?
> - If you have a handle to a bit or part select that is out of range, what
> is it's value?
> I think your second proposal should be added to all the routines to cover
> the remaining situations, so people know how to handle errors.
> Garnett, Jim wrote:
> > All,
> > I wanted to provide a preliminary proposal as a first attempt to present
> > a proposal to an open PTF errata.
> > PTF Errata 517
> > Synopsis : 27.14: No discussion on what to return if there is no value
> > for an object
> > Description : vpi_get_value() has no description of what happens if
> > there is no value
> > at any point for an object passed to it. For example,
> > what happens if
> > you pass it a handle to something that does not have a
> > value such as a
> > vpiModule object? What if simulation has not started
> > yet. What is the
> > value of a net at that point? After simulation has finished?
> > Discussion : In looking into this issue, it seems that there are other
> > vpi_get_... functions
> > (vpi_get_systf_info, vpi_get_delays, and vpi_get_cb_info)
> > that don't provide
> > any information on what is returned if the "obj" passed to
> > it is invalid. These
> > other functions are not quite as unique as vpi_get_value
> > in that its data
> > structure (s_vpi_value) has a union with a wide variety of
> > types. This wide
> > variety of types is what would make it difficult to pass a
> > known "invalid" value
> > back. But in general, all the functions must allocate the
> > data structure that is
> > used for passing data and none of the functions explicitly
> > describe what is
> > returned when an invalid obj is passed in.
> > Proposal : I see two possible proposals (that could and maybe should
> > apply to all vpi_get...
> > functions mentioned above);
> > Proposal 1 : Basically change nothing. This is based on the premise
> > that the only way to know
> > for sure if the vpi_get_value function returned a valid
> > value or not is to check
> > to see if an error occurred with vpi_chk_error(). This
> > would assume that the user
> > looking at the documentation would know that
> > vpi_chk_error existed and why/how
> > to use the function.
> > Proposal 2 : Add text to the vpi_get_value description that states
> > that the user needs to check
> > vpi_chk_error to ensure that the prior call was
> > successful and thus the data
> > structure is valid. The text could be as follows:
> > To ensure that a valid s_vpi_value structure
> > exists and an error did not occur,
> > the vpi_chk_error routine should subsequently be
> > called.
> > and appended to the end of the first paragraph of the
> > vpi_get_value description.
> > Any feedback is appceciated.
> > -- Jim Garnett
> Charles Dawson
> Senior Engineering Manager
> NC-Verilog Team
> Cadence Design Systems, Inc.
> 270 Billerica Road
> Chelmsford, MA 01824
> (978) 262 - 6273
-- Shalom Bresticker Shalom.Bresticker @freescale.com Design & Reuse Methodology Tel: +972 9 9522268 Freescale Semiconductor Israel, Ltd. Fax: +972 9 9522890 POB 2208, Herzlia 46120, ISRAEL Cell: +972 50 5441478
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