RE: [sv-ec] Queue Methods - return status?

Hi,

I agree that these should be treated as invalid reads and writes, but I disagree where Arturo says, "an assertion may be issued".

For invalid writes, the LRM says, "An invalid index (i.e., a 4-state expression with X's or Z's, or a value that lies outside 0...$+1) shall cause a write operation to be ignored and a run-time warning to be issued," i.e., a warning is mandatory.

For invalid reads, the LRM says, "An invalid index value (i.e., a 4-state expression with X's or Z's, or a value that lies outside 0...$) shall cause a read operation (e = Q[n]) to return the default initial value for the type of queue item," with no mention of a warning. Of course, nothing prevents a tool from issuing such a warning, but it is not in the LRM.

Regards,
Shalom

> -----Original Message-----
> From: owner-sv-ec@server.eda.org 
> [mailto:owner-sv-ec@server.eda.org] On Behalf Of Arturo Salz
> Sent: Wednesday, June 17, 2009 11:43 AM
> To: Clifford E. Cummings; sv-ec@eda.org
> Subject: RE: [sv-ec] Queue Methods - return status?
> 
> Hi Cliff,
> 
> Interesting question. Here are my two cents:
> 
> Calling insert() with an invalid index - either larger than 
> $+1, negative, or containing X or Z - behaves the same as any 
> other array write with an invalid, that is, no write is 
> performed and an assertion may be issued.
> 
> Calling delete() with an invalid index deletes no element and 
> an assertion may be issued. This behavior is consistent with 
> the above.
> 
> Calling pop_front() or pop_back() on an empty queue returns 
> the default uninitialized value for the queue element type, 
> and an assertion may be issued. This is consistent with an 
> array read with an invalid index.
> 
> These seem rather natural extensions from other array 
> operations. Nonetheless, it would be good to document them.
> 
>         Arturo
> 
> 
> -----Original Message-----
> From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On 
> Behalf Of Clifford E. Cummings
> Sent: Tuesday, June 16, 2009 8:35 PM
> To: sv-ec@eda.org
> Subject: [sv-ec] Queue Methods - return status?
> 
> Hi, All -
> 
> This question has been posed to me a number of times and I am not
> 100% sure what the answer should be.
> 
> Do the queue methods return any type of status if they fail? Looking
> over the LRM (clause 7.11.2 in Ballot Draft), the methods are
> described, but unlike mailbox methods, there does not appear to be
> any return status, nor is there any description of what should happen
> if the called methods fail.
> 
> Examples:
> insert() method at an index. What happens if you try to insert into a
> queue at location 5 if there are only two entries in the queue? And
> where is the behavior described. This is a void function.
> 
> delete() method at an index. Same type of issue. Deleting an entry
> that does not exist.
> 
> pop_front() or pop_back() from an empty queue. What happens? 
> Any status?
> 
> The push_front(), push_back() and size() methods should all be okay.
> 
> Thanks for any thoughts.
> 
> Regards - Cliff
> 
> 
> ----------------------------------------------------
> Cliff Cummings - Sunburst Design, Inc.
> 14314 SW Allen Blvd., PMB 501, Beaverton, OR 97005
> Phone: 503-641-8446 / FAX: 503-641-8486
> cliffc@sunburst-design.com / www.sunburst-design.com
> Expert Verilog, SystemVerilog, Synthesis and Verification Training
> 
> 
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